diff --git a/.gitmodules b/.gitmodules
index 6244b3c095186..fbebccf408fb6 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -33,3 +33,6 @@
 [submodule "src/libcompiler_builtins"]
 	path = src/libcompiler_builtins
 	url = https://github.com/rust-lang-nursery/compiler-builtins
+[submodule "src/tools/clippy"]
+	path = src/tools/clippy
+	url = https://github.com/rust-lang-nursery/rust-clippy.git
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index c424ca7ab009e..7441d51055ffb 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -232,7 +232,34 @@ Some common invocations of `x.py` are:
   guidelines as of yet, but basic rules like 4 spaces for indentation and no
   more than 99 characters in a single line should be kept in mind when writing
   code.
-- `rustup toolchain link <name> build/<host-triple>/<stage>` - Use the custom compiler build via [rustup](https://github.com/rust-lang-nursery/rustup.rs#working-with-custom-toolchains-and-local-builds).
+
+### Using your local build
+
+If you use Rustup to manage your rust install, it has a feature called ["custom
+toolchains"][toolchain-link] that you can use to access your newly-built compiler
+without having to install it to your system or user PATH. If you've run `python
+x.py build`, then you can add your custom rustc to a new toolchain like this:
+
+[toolchain-link]: https://github.com/rust-lang-nursery/rustup.rs#working-with-custom-toolchains-and-local-builds
+
+```
+rustup toolchain link <name> build/<host-triple>/stage2
+```
+
+Where `<host-triple>` is the build triple for the host (the triple of your
+computer, by default), and `<name>` is the name for your custom toolchain. (If you
+added `--stage 1` to your build command, the compiler will be in the `stage1`
+folder instead.) You'll only need to do this once - it will automatically point
+to the latest build you've done.
+
+Once this is set up, you can use your custom toolchain just like any other. For
+example, if you've named your toolchain `local`, running `cargo +local build` will
+compile a project with your custom rustc, setting `rustup override set local` will
+override the toolchain for your current directory, and `cargo +local doc` will use
+your custom rustc and rustdoc to generate docs. (If you do this with a `--stage 1`
+build, you'll need to build rustdoc specially, since it's not normally built in
+stage 1. `python x.py build --stage 1 src/libstd src/tools/rustdoc` will build
+rustdoc and libstd, which will allow rustdoc to be run with that toolchain.)
 
 ## Pull Requests
 
@@ -298,6 +325,32 @@ Speaking of tests, Rust has a comprehensive test suite. More information about
 it can be found
 [here](https://github.com/rust-lang/rust-wiki-backup/blob/master/Note-testsuite.md).
 
+### External Dependencies
+
+Currently building Rust will also build the following external projects:
+
+* [clippy](https://github.com/rust-lang-nursery/rust-clippy)
+
+If your changes break one of these projects, you need to fix them by opening
+a pull request against the broken project. When you have opened a pull request,
+you can point the submodule at your pull request by calling
+
+```
+git fetch origin pull/$id_of_your_pr/head:my_pr
+git checkout my_pr
+```
+
+within the submodule's directory. Don't forget to also add your changes with
+
+```
+git add path/to/submodule
+```
+
+outside the submodule.
+
+It can also be more convenient during development to set `submodules = false`
+in the `config.toml` to prevent `x.py` from resetting to the original branch.
+
 ## Writing Documentation
 
 Documentation improvements are very welcome. The source of `doc.rust-lang.org`
diff --git a/RELEASES.md b/RELEASES.md
index c3a7367a2ee54..5815cb0f97260 100644
--- a/RELEASES.md
+++ b/RELEASES.md
@@ -3,7 +3,7 @@ Version 1.20.0 (2017-08-31)
 
 Language
 --------
-- [Associated constants in traits is now stabilised.][42809]
+- [Associated constants are now stabilised.][42809]
 - [A lot of macro bugs are now fixed.][42913]
 
 Compiler
@@ -77,7 +77,7 @@ Stabilized APIs
 - [`slice::sort_unstable_by_key`]
 - [`slice::sort_unstable_by`]
 - [`slice::sort_unstable`]
-- [`ste::from_boxed_utf8_unchecked`]
+- [`str::from_boxed_utf8_unchecked`]
 - [`str::as_bytes_mut`]
 - [`str::as_bytes_mut`]
 - [`str::from_utf8_mut`]
diff --git a/config.toml.example b/config.toml.example
index fd1f03b9d0e24..3f5101ebf342f 100644
--- a/config.toml.example
+++ b/config.toml.example
@@ -73,6 +73,10 @@
 # controlled by rustbuild's -j parameter.
 #link-jobs = 0
 
+# When invoking `llvm-config` this configures whether the `--shared` argument is
+# passed to prefer linking to shared libraries.
+#link-shared = false
+
 # =============================================================================
 # General build configuration options
 # =============================================================================
@@ -166,6 +170,15 @@
 # to +10 on Unix platforms, and by using a "low priority" job object on Windows.
 #low-priority = false
 
+# Arguments passed to the `./configure` script, used during distcheck. You
+# probably won't fill this in but rather it's filled in by the `./configure`
+# script.
+#configure-args = []
+
+# Indicates that a local rebuild is ocurring instead of a full bootstrap,
+# essentially skipping stage0 as the local compiler is recompiling itself again.
+#local-rebuild = false
+
 # =============================================================================
 # General install configuration options
 # =============================================================================
@@ -195,6 +208,13 @@
 # =============================================================================
 [rust]
 
+# Indicates that the build should be optimized for debugging Rust. Note that
+# this is typically not what you want as it takes an incredibly large amount of
+# time to have a debug-mode rustc compile any code (notably libstd). If this
+# value is set to `true` it will affect a number of configuration options below
+# as well, if unconfigured.
+#debug = false
+
 # Whether or not to optimize the compiler and standard library
 # Note: the slowness of the non optimized compiler compiling itself usually
 #       outweighs the time gains in not doing optimizations, therefore a
@@ -249,6 +269,10 @@
 # desired in distributions, for example.
 #rpath = true
 
+# Suppresses extraneous output from tests to ensure the output of the test
+# harness is relatively clean.
+#quiet-tests = false
+
 # Flag indicating whether tests are compiled with optimizations (the -O flag) or
 # with debuginfo (the -g flag)
 #optimize-tests = true
@@ -259,7 +283,13 @@
 #codegen-tests = true
 
 # Flag indicating whether git info will be retrieved from .git automatically.
-#ignore-git = false
+# Having the git information can cause a lot of rebuilds during development.
+# Note: If this attribute is not explicity set (e.g. if left commented out) it
+# will default to true if channel = "dev", but will default to false otherwise.
+#ignore-git = true
+
+# When creating source tarballs whether or not to create a source tarball.
+#dist-src = false
 
 # =============================================================================
 # Options for specific targets
@@ -304,6 +334,10 @@
 # linked binaries
 #musl-root = "..."
 
+# Used in testing for configuring where the QEMU images are located, you
+# probably don't want to use this.
+#qemu-rootfs = "..."
+
 # =============================================================================
 # Distribution options
 #
diff --git a/configure b/configure
index 664b473b2c9d0..eeb8d081d3454 100755
--- a/configure
+++ b/configure
@@ -1,779 +1,17 @@
 #!/bin/sh
 
-# /bin/sh on Solaris is not a POSIX compatible shell, but /usr/bin/bash is.
-if [ `uname -s` = 'SunOS' -a "${POSIX_SHELL}" != "true" ]; then
-    POSIX_SHELL="true"
-    export POSIX_SHELL
-    exec /usr/bin/env bash $0 "$@"
-fi
-unset POSIX_SHELL # clear it so if we invoke other scripts, they run as bash as well
+script="$(dirname $0)"/src/bootstrap/configure.py
 
-msg() {
-    echo "configure: $*"
-}
-
-step_msg() {
-    msg
-    msg "$1"
-    msg
-}
-
-warn() {
-    echo "configure: WARNING: $1"
-}
-
-err() {
-    echo "configure: error: $1"
-    exit 1
-}
-
-run() {
-    msg "$@"
-    "$@"
-}
-
-need_ok() {
-    if [ $? -ne 0 ]
-    then
-        err "$1"
-    fi
-}
-
-need_cmd() {
-    if command -v $1 >/dev/null 2>&1
-    then msg "found program '$1'"
-    else err "program '$1' is missing, please install it"
-    fi
-}
-
-make_dir() {
-    if [ ! -d $1 ]
-    then
-        run mkdir -p $1
-    fi
-}
-
-copy_if_changed() {
-    if cmp -s $1 $2
-    then
-        msg "leaving $2 unchanged"
-    else
-        run cp -f $1 $2
-        chmod u-w $2 # make copied artifact read-only
-    fi
-}
-
-move_if_changed() {
-    if cmp -s $1 $2
-    then
-        msg "leaving $2 unchanged"
-    else
-        run mv -f $1 $2
-        chmod u-w $2 # make moved artifact read-only
-    fi
-}
-
-putvar() {
-    local T
-    eval T=\$$1
-    eval TLEN=\${#$1}
-    if [ $TLEN -gt 35 ]
-    then
-        printf "configure: %-20s := %.35s ...\n" $1 "$T"
-    else
-        printf "configure: %-20s := %s %s\n" $1 "$T" "$2"
-    fi
-    printf "%-20s := %s\n" $1 "$T" >>config.tmp
-}
-
-putpathvar() {
-    local T
-    eval T=\$$1
-    eval TLEN=\${#$1}
-    if [ $TLEN -gt 35 ]
-    then
-        printf "configure: %-20s := %.35s ...\n" $1 "$T"
-    else
-        printf "configure: %-20s := %s %s\n" $1 "$T" "$2"
-    fi
-    if [ -z "$T" ]
-    then
-        printf "%-20s := \n" $1 >>config.tmp
-    else
-        printf "%-20s := \"%s\"\n" $1 "$T" >>config.tmp
-    fi
-}
-
-probe() {
-    local V=$1
+try() {
+    cmd=$1
     shift
-    local P
-    local T
-    for P
-    do
-        T=$(command -v $P 2>&1)
-        if [ $? -eq 0 ]
-        then
-            VER0=$($P --version 2>/dev/null \
-                |  grep -o '[vV]\?[0-9][0-9.][a-z0-9.-]*' | head -1 )
-            if [ $? -eq 0 -a "x${VER0}" != "x" ]
-            then
-              VER="($VER0)"
-            else
-              VER=""
-            fi
-            break
-        else
-            VER=""
-            T=""
-        fi
-    done
-    eval $V=\$T
-    putpathvar $V "$VER"
-}
-
-probe_need() {
-    probe $*
-    local V=$1
-    shift
-    eval VV=\$$V
-    if [ -z "$VV" ]
-    then
-        err "$V needed, but unable to find any of: $*"
-    fi
-}
-
-validate_opt () {
-    for arg in $CFG_CONFIGURE_ARGS
-    do
-        isArgValid=0
-        for option in $BOOL_OPTIONS
-        do
-            if test --disable-$option = $arg
-            then
-                isArgValid=1
-            fi
-            if test --enable-$option = $arg
-            then
-                isArgValid=1
-            fi
-        done
-        for option in $VAL_OPTIONS
-        do
-            if echo "$arg" | grep -q -- "--$option="
-            then
-                isArgValid=1
-            fi
-        done
-        if [ "$arg" = "--help" ]
-        then
-            echo
-            echo "No more help available for Configure options,"
-            echo "check the Wiki or join our IRC channel"
-            break
-        else
-            if test $isArgValid -eq 0
-            then
-                err "Option '$arg' is not recognized"
-            fi
-        fi
-    done
-}
-
-# `valopt OPTION_NAME DEFAULT DOC` extracts a string-valued option
-# from command line, using provided default value for the option if
-# not present, and saves it to the generated config.mk.
-#
-# `valopt_nosave` is much the same, except that it does not save the
-# result to config.mk (instead the script should use `putvar` itself
-# later on to save it).  `valopt_core` is the core upon which the
-# other two are built.
-
-valopt_core() {
-    VAL_OPTIONS="$VAL_OPTIONS $2"
-
-    local SAVE=$1
-    local OP=$2
-    local DEFAULT=$3
-    shift
-    shift
-    shift
-    local DOC="$*"
-    if [ $HELP -eq 0 ]
-    then
-        local UOP=$(echo $OP | tr '[:lower:]' '[:upper:]' | tr '\-' '\_')
-        local V="CFG_${UOP}"
-        local V_PROVIDED="${V}_PROVIDED"
-        eval $V="$DEFAULT"
-        for arg in $CFG_CONFIGURE_ARGS
-        do
-            if echo "$arg" | grep -q -- "--$OP="
-            then
-                val=$(echo "$arg" | cut -f2 -d=)
-                eval $V=$val
-                eval $V_PROVIDED=1
-            fi
-        done
-        if [ "$SAVE" = "save" ]
-        then
-            putvar $V
-        fi
-    else
-        if [ -z "$DEFAULT" ]
-        then
-            DEFAULT="<none>"
-        fi
-        OP="${OP}=[${DEFAULT}]"
-        printf "    --%-30s %s\n" "$OP" "$DOC"
-    fi
-}
-
-valopt_nosave() {
-    valopt_core nosave "$@"
-}
-
-valopt() {
-    valopt_core save "$@"
-}
-
-# `opt OPTION_NAME DEFAULT DOC` extracts a boolean-valued option from
-# command line, using the provided default value (0/1) for the option
-# if not present, and saves it to the generated config.mk.
-#
-# `opt_nosave` is much the same, except that it does not save the
-# result to config.mk (instead the script should use `putvar` itself
-# later on to save it).  `opt_core` is the core upon which the other
-# two are built.
-
-opt_core() {
-    BOOL_OPTIONS="$BOOL_OPTIONS $2"
-
-    local SAVE=$1
-    local OP=$2
-    local DEFAULT=$3
-    shift
-    shift
-    shift
-    local DOC="$*"
-    local FLAG=""
-
-    if [ $DEFAULT -eq 0 ]
-    then
-        FLAG="enable"
-        DEFAULT_FLAG="disable"
-    else
-        FLAG="disable"
-        DEFAULT_FLAG="enable"
-        DOC="don't $DOC"
-    fi
-
-    if [ $HELP -eq 0 ]
-    then
-        for arg in $CFG_CONFIGURE_ARGS
-        do
-            if [ "$arg" = "--${FLAG}-${OP}" ]
-            then
-                OP=$(echo $OP | tr 'a-z-' 'A-Z_')
-                FLAG=$(echo $FLAG | tr 'a-z' 'A-Z')
-                local V="CFG_${FLAG}_${OP}"
-                local V_PROVIDED="CFG_${FLAG}_${OP}_PROVIDED"
-                eval $V=1
-                eval $V_PROVIDED=1
-                if [ "$SAVE" = "save" ]
-                then
-                   putvar $V
-                fi
-            elif [ "$arg" = "--${DEFAULT_FLAG}-${OP}" ]
-            then
-                OP=$(echo $OP | tr 'a-z-' 'A-Z_')
-                DEFAULT_FLAG=$(echo $DEFAULT_FLAG | tr 'a-z' 'A-Z')
-                local V_PROVIDED="CFG_${DEFAULT_FLAG}_${OP}_PROVIDED"
-                eval $V_PROVIDED=1
-            fi
-        done
-    else
-        if [ -n "$META" ]
-        then
-            OP="$OP=<$META>"
-        fi
-        printf "    --%-30s %s\n" "$FLAG-$OP" "$DOC"
-     fi
-}
-
-opt_nosave() {
-    opt_core nosave "$@"
-}
-
-opt() {
-    opt_core save "$@"
-}
-
-envopt() {
-    local NAME=$1
-    local V="CFG_${NAME}"
-    eval VV=\$$V
-
-    # If configure didn't set a value already, then check environment.
-    #
-    # (It is recommended that the configure script always check the
-    # environment before setting any values to envopt variables; see
-    # e.g.  how CFG_CC is handled, where it first checks `-z "$CC"`,
-    # and issues msg if it ends up employing that provided value.)
-    if [ -z "$VV" ]
-    then
-        eval $V=\$$NAME
-        eval VV=\$$V
-    fi
-
-    # If script or environment provided a value, save it.
-    if [ -n "$VV" ]
-    then
-        putvar $V
-    fi
-}
-
-enable_if_not_disabled() {
-    local OP=$1
-    local UOP=$(echo $OP | tr '[:lower:]' '[:upper:]' | tr '\-' '\_')
-    local ENAB_V="CFG_ENABLE_$UOP"
-    local EXPLICITLY_DISABLED="CFG_DISABLE_${UOP}_PROVIDED"
-    eval VV=\$$EXPLICITLY_DISABLED
-    if [ -z "$VV" ]; then
-        eval $ENAB_V=1
+    T=$($cmd --version 2>/dev/null)
+    if [ $? -eq 0 ]; then
+        exec $cmd "$script" "$@"
     fi
 }
 
-to_gnu_triple() {
-    case $1 in
-        i686-pc-windows-gnu) echo i686-w64-mingw32 ;;
-        x86_64-pc-windows-gnu) echo x86_64-w64-mingw32 ;;
-        *) echo $1 ;;
-    esac
-}
-
-# Prints the absolute path of a directory to stdout
-abs_path() {
-    local _path="$1"
-    # Unset CDPATH because it causes havok: it makes the destination unpredictable
-    # and triggers 'cd' to print the path to stdout. Route `cd`'s output to /dev/null
-    # for good measure.
-    (unset CDPATH && cd "$_path" > /dev/null && pwd)
-}
-
-HELP=0
-for arg; do
-    case "$arg" in
-        --help) HELP=1;;
-    esac
-done
-
-msg "looking for configure programs"
-need_cmd cmp
-need_cmd mkdir
-need_cmd printf
-need_cmd cut
-need_cmd head
-need_cmd grep
-need_cmd xargs
-need_cmd cp
-need_cmd find
-need_cmd uname
-need_cmd date
-need_cmd tr
-need_cmd sed
-need_cmd file
-need_cmd make
-
-CFG_SRC_DIR="$(abs_path $(dirname $0))/"
-CFG_SRC_DIR_RELATIVE="$(dirname $0)/"
-CFG_BUILD_DIR="$(pwd)/"
-CFG_SELF="$0"
-CFG_CONFIGURE_ARGS="$@"
-
-
-case "${CFG_SRC_DIR}" in
-    *\ * )
-        err "The path to the rust source directory contains spaces, which is not supported"
-        ;;
-    *)
-        ;;
-esac
-
-
-OPTIONS=""
-if [ "$HELP" -eq 1 ]
-then
-    echo
-    echo "Usage: $CFG_SELF [options]"
-    echo
-    echo "Options:"
-    echo
-else
-    msg "recreating config.tmp"
-    echo '' >config.tmp
-
-    step_msg "processing $CFG_SELF args"
-fi
-
-BOOL_OPTIONS=""
-VAL_OPTIONS=""
-
-opt debug 0 "debug mode; disables optimization unless \`--enable-optimize\` given"
-opt valgrind 0 "run tests with valgrind (memcheck by default)"
-opt helgrind 0 "run tests with helgrind instead of memcheck"
-opt valgrind-rpass 1 "run rpass-valgrind tests with valgrind"
-opt docs     1 "build standard library documentation"
-opt compiler-docs     0 "build compiler documentation"
-opt optimize-tests 1 "build tests with optimizations"
-opt debuginfo-tests 0 "build tests with debugger metadata"
-opt quiet-tests 0 "enable quieter output when running tests"
-opt libcpp 1 "build llvm with libc++ instead of libstdc++ when using clang"
-opt llvm-assertions 0 "build LLVM with assertions"
-opt debug-assertions 0 "build with debugging assertions"
-opt fast-make 0 "use .gitmodules as timestamp for submodule deps"
-opt ccache 0 "invoke gcc/clang via ccache to reuse object files between builds"
-opt sccache 0 "invoke gcc/clang via sccache to reuse object files between builds"
-opt local-rust 0 "use an installed rustc rather than downloading a snapshot"
-opt local-rebuild 0 "assume local-rust matches the current version, for rebuilds; implies local-rust, and is implied if local-rust already matches the current version"
-opt llvm-static-stdcpp 0 "statically link to libstdc++ for LLVM"
-opt llvm-link-shared 0 "prefer shared linking to LLVM (llvm-config --link-shared)"
-opt rpath 1 "build rpaths into rustc itself"
-opt stage0-landing-pads 1 "enable landing pads during bootstrap with stage0"
-# This is used by the automation to produce single-target nightlies
-opt dist-host-only 0 "only install bins for the host architecture"
-opt inject-std-version 1 "inject the current compiler version of libstd into programs"
-opt llvm-version-check 1 "check if the LLVM version is supported, build anyway"
-opt codegen-tests 1 "run the src/test/codegen tests"
-opt option-checking 1 "complain about unrecognized options in this configure script"
-opt ninja 0 "build LLVM using the Ninja generator (for MSVC, requires building in the correct environment)"
-opt locked-deps 0 "force Cargo.lock to be up to date"
-opt vendor 0 "enable usage of vendored Rust crates"
-opt sanitizers 0 "build the sanitizer runtimes (asan, lsan, msan, tsan)"
-opt dist-src 1 "when building tarballs enables building a source tarball"
-opt cargo-openssl-static 0 "static openssl in cargo"
-opt profiler 0 "build the profiler runtime"
-
-# Optimization and debugging options. These may be overridden by the release channel, etc.
-opt_nosave optimize 1 "build optimized rust code"
-opt_nosave optimize-cxx 1 "build optimized C++ code"
-opt_nosave optimize-llvm 1 "build optimized LLVM"
-opt_nosave llvm-assertions 0 "build LLVM with assertions"
-opt_nosave debug-assertions 0 "build with debugging assertions"
-opt_nosave llvm-release-debuginfo 0 "build LLVM with debugger metadata"
-opt_nosave debuginfo 0 "build with debugger metadata"
-opt_nosave debuginfo-lines 0 "build with line number debugger metadata"
-opt_nosave debuginfo-only-std 0 "build only libstd with debugging information"
-opt_nosave debug-jemalloc 0 "build jemalloc with --enable-debug --enable-fill"
-
-valopt localstatedir "/var/lib" "local state directory"
-valopt sysconfdir "/etc" "install system configuration files"
-
-valopt datadir "${CFG_PREFIX}/share" "install data"
-valopt infodir "${CFG_PREFIX}/share/info" "install additional info"
-valopt llvm-root "" "set LLVM root"
-valopt python "" "set path to python"
-valopt jemalloc-root "" "set directory where libjemalloc_pic.a is located"
-valopt build "" "GNUs ./configure syntax LLVM build triple"
-valopt android-cross-path "" "Android NDK standalone path (deprecated)"
-valopt i686-linux-android-ndk "" "i686-linux-android NDK standalone path"
-valopt arm-linux-androideabi-ndk "" "arm-linux-androideabi NDK standalone path"
-valopt armv7-linux-androideabi-ndk "" "armv7-linux-androideabi NDK standalone path"
-valopt aarch64-linux-android-ndk "" "aarch64-linux-android NDK standalone path"
-valopt x86_64-linux-android-ndk "" "x86_64-linux-android NDK standalone path"
-valopt nacl-cross-path  "" "NaCl SDK path (Pepper Canary is recommended). Must be absolute!"
-valopt musl-root "/usr/local" "MUSL root installation directory (deprecated)"
-valopt musl-root-x86_64 "" "x86_64-unknown-linux-musl install directory"
-valopt musl-root-i686 "" "i686-unknown-linux-musl install directory"
-valopt musl-root-arm "" "arm-unknown-linux-musleabi install directory"
-valopt musl-root-armhf "" "arm-unknown-linux-musleabihf install directory"
-valopt musl-root-armv7 "" "armv7-unknown-linux-musleabihf install directory"
-valopt extra-filename "" "Additional data that is hashed and passed to the -C extra-filename flag"
-valopt qemu-armhf-rootfs "" "rootfs in qemu testing, you probably don't want to use this"
-valopt qemu-aarch64-rootfs "" "rootfs in qemu testing, you probably don't want to use this"
-valopt experimental-targets "" "experimental LLVM targets to build"
-
-if [ -e ${CFG_SRC_DIR}.git ]
-then
-    valopt release-channel "dev" "the name of the release channel to build"
-else
-    # If we have no git directory then we are probably a tarball distribution
-    # and should default to stable channel - Issue 28322
-    probe CFG_GIT          git
-    msg "git: no git directory. Changing default release channel to stable"
-    valopt release-channel "stable" "the name of the release channel to build"
-fi
-
-# Used on systems where "cc" and "ar" are unavailable
-valopt default-linker "cc" "the default linker"
-valopt default-ar     "ar" "the default ar"
-
-# Many of these are saved below during the "writing configuration" step
-# (others are conditionally saved).
-opt_nosave manage-submodules 1 "let the build manage the git submodules"
-opt_nosave clang 0 "prefer clang to gcc for building the runtime"
-opt_nosave jemalloc 1 "build liballoc with jemalloc"
-opt full-bootstrap 0 "build three compilers instead of two"
-opt extended 0 "build an extended rust tool set"
-
-valopt_nosave prefix "/usr/local" "set installation prefix"
-valopt_nosave local-rust-root "/usr/local" "set prefix for local rust binary"
-valopt_nosave host "${CFG_BUILD}" "GNUs ./configure syntax LLVM host triples"
-valopt_nosave target "${CFG_HOST}" "GNUs ./configure syntax LLVM target triples"
-valopt_nosave mandir "${CFG_PREFIX}/share/man" "install man pages in PATH"
-valopt_nosave docdir "${CFG_PREFIX}/share/doc/rust" "install documentation in PATH"
-valopt_nosave bindir "${CFG_PREFIX}/bin" "install binaries"
-
-# On Windows this determines root of the subtree for target libraries.
-# Host runtime libs always go to 'bin'.
-valopt libdir "${CFG_PREFIX}/lib" "install libraries"
-
-case "$CFG_LIBDIR" in
-    "$CFG_PREFIX"/*) CAT_INC=2;;
-    "$CFG_PREFIX"*)  CAT_INC=1;;
-    *)
-        err "libdir must begin with the prefix. Use --prefix to set it accordingly.";;
-esac
-
-CFG_LIBDIR_RELATIVE=`echo ${CFG_LIBDIR} | cut -c$((${#CFG_PREFIX}+${CAT_INC}))-`
-
-if [ $HELP -eq 1 ]
-then
-    echo
-    exit 0
-fi
-
-# Validate Options
-if [ -z "$CFG_DISABLE_OPTION_CHECKING" ]
-then
-    step_msg "validating $CFG_SELF args"
-    validate_opt
-fi
-
-# Validate the release channel, and configure options
-case "$CFG_RELEASE_CHANNEL" in
-    nightly )
-	msg "overriding settings for $CFG_RELEASE_CHANNEL"
-        enable_if_not_disabled llvm-assertions
-        # FIXME(stage0) re-enable this on the next stage0 now that #35566 is
-        # fixed
-        case "$CFG_BUILD" in
-          *-pc-windows-gnu)
-            ;;
-          *)
-            enable_if_not_disabled debuginfo-lines
-            enable_if_not_disabled debuginfo-only-std
-            ;;
-        esac
-
-	;;
-    beta | stable)
-	msg "overriding settings for $CFG_RELEASE_CHANNEL"
-        case "$CFG_BUILD" in
-          *-pc-windows-gnu)
-            ;;
-          *)
-            enable_if_not_disabled debuginfo-lines
-            enable_if_not_disabled debuginfo-only-std
-            ;;
-        esac
-	;;
-    dev)
-	;;
-    *)
-        err "release channel must be 'dev', 'nightly', 'beta' or 'stable'"
-        ;;
-esac
-
-# Adjust perf and debug options for debug mode
-if [ -n "$CFG_ENABLE_DEBUG" ]; then
-    msg "debug mode enabled, setting performance options"
-    if [ -z "$CFG_ENABLE_OPTIMIZE_PROVIDED" ]; then
-        msg "optimization not explicitly enabled, disabling optimization"
-        CFG_DISABLE_OPTIMIZE=1
-        CFG_DISABLE_OPTIMIZE_CXX=1
-    fi
-
-    # Set following variables to 1 unless setting already provided
-    enable_if_not_disabled debug-assertions
-    enable_if_not_disabled debug-jemalloc
-    enable_if_not_disabled debuginfo
-    enable_if_not_disabled llvm-assertions
-fi
-
-# OK, now write the debugging options
-if [ -n "$CFG_DISABLE_OPTIMIZE" ]; then putvar CFG_DISABLE_OPTIMIZE; fi
-if [ -n "$CFG_DISABLE_OPTIMIZE_CXX" ]; then putvar CFG_DISABLE_OPTIMIZE_CXX; fi
-if [ -n "$CFG_DISABLE_OPTIMIZE_LLVM" ]; then putvar CFG_DISABLE_OPTIMIZE_LLVM; fi
-if [ -n "$CFG_ENABLE_LLVM_ASSERTIONS" ]; then putvar CFG_ENABLE_LLVM_ASSERTIONS; fi
-if [ -n "$CFG_ENABLE_DEBUG_ASSERTIONS" ]; then putvar CFG_ENABLE_DEBUG_ASSERTIONS; fi
-if [ -n "$CFG_ENABLE_LLVM_RELEASE_DEBUGINFO" ]; then putvar CFG_ENABLE_LLVM_RELEASE_DEBUGINFO; fi
-if [ -n "$CFG_ENABLE_DEBUGINFO" ]; then putvar CFG_ENABLE_DEBUGINFO; fi
-if [ -n "$CFG_ENABLE_DEBUGINFO_LINES" ]; then putvar CFG_ENABLE_DEBUGINFO_LINES; fi
-if [ -n "$CFG_ENABLE_DEBUGINFO_ONLY_STD" ]; then putvar CFG_ENABLE_DEBUGINFO_ONLY_STD; fi
-if [ -n "$CFG_ENABLE_DEBUG_JEMALLOC" ]; then putvar CFG_ENABLE_DEBUG_JEMALLOC; fi
-
-step_msg "looking for build programs"
-
-probe_need CFG_CURL curl
-if [ -z "$CFG_PYTHON_PROVIDED" ]; then
-    probe_need CFG_PYTHON      python2.7 python2 python
-fi
-
-python_version=$($CFG_PYTHON -V 2>&1)
-if [ $(echo $python_version | grep -c '^Python 2\.7') -ne 1 ]; then
-    err "Found $python_version, but Python 2.7 is required"
-fi
-
-# the valgrind rpass tests will fail if you don't have a valgrind, but they're
-# only disabled if you opt out.
-if [ -z "$CFG_VALGRIND" ]
-then
-    # If the user has explicitly asked for valgrind tests, then fail
-    if [ -n "$CFG_ENABLE_VALGRIND" ] && [ -n "$CFG_ENABLE_VALGRIND_PROVIDED" ]
-    then
-        err "No valgrind present, but valgrind tests explicitly requested"
-    else
-        CFG_DISABLE_VALGRIND_RPASS=1
-        putvar CFG_DISABLE_VALGRIND_RPASS
-    fi
-fi
-
-# Do some sanity checks if running on buildbot
-# (these env vars are set by rust-buildbot)
-if [ -n "$RUST_DIST_SERVER" -a -n "$ALLOW_NONZERO_RLIMIT_CORE" ]; then
-   # Frequently the llvm submodule directory is broken by the build
-   # being killed
-   llvm_lock="${CFG_SRC_DIR}/.git/modules/src/llvm/index.lock"
-   if [ -e "$llvm_lock" ]; then
-       step_msg "removing $llvm_lock"
-       rm -f "$llvm_lock"
-   fi
-fi
-
-BIN_SUF=
-if [ "$CFG_OSTYPE" = "pc-windows-gnu" ] || [ "$CFG_OSTYPE" = "pc-windows-msvc" ]
-then
-    BIN_SUF=.exe
-fi
-
-# --enable-local-rebuild implies --enable-local-rust too
-if [ -n "$CFG_ENABLE_LOCAL_REBUILD" ]
-then
-    if [ -z "$CFG_ENABLE_LOCAL_RUST" ]
-    then
-        CFG_ENABLE_LOCAL_RUST=1
-        putvar CFG_ENABLE_LOCAL_RUST
-    fi
-fi
-
-if [ -n "$CFG_ENABLE_LOCAL_RUST" ]
-then
-    system_rustc=$(which rustc)
-    if [ -f ${CFG_LOCAL_RUST_ROOT}/bin/rustc${BIN_SUF} ]
-    then
-        : # everything already configured
-    elif [ -n "$system_rustc" ]
-    then
-        # we assume that rustc is in a /bin directory
-        CFG_LOCAL_RUST_ROOT=${system_rustc%/bin/rustc}
-    else
-        err "no local rust to use"
-    fi
-
-    CMD="${CFG_LOCAL_RUST_ROOT}/bin/rustc${BIN_SUF}"
-    LRV=`LD_LIBRARY_PATH=${CFG_LOCAL_RUST_ROOT}/lib $CMD --version`
-    if [ $? -ne 0 ]
-    then
-        step_msg "failure while running $CMD --version"
-        exit 1
-    fi
-    step_msg "using rustc at: ${CFG_LOCAL_RUST_ROOT} with version: $LRV"
-    putvar CFG_LOCAL_RUST_ROOT
-fi
-
-# Same with jemalloc.  save the setting here.
-if [ -n "$CFG_DISABLE_JEMALLOC" ]
-then
-    putvar CFG_DISABLE_JEMALLOC
-fi
-
-# All safeguards based on $CFG_ENABLE_CLANG should occur before this
-# point in the script; after this point, script logic should inspect
-# $CFG_USING_CLANG rather than $CFG_ENABLE_CLANG.
-
-# Set CFG_{CC,CXX,CPP,CFLAGS,CXXFLAGS,LDFLAGS}
-envopt CC
-envopt CXX
-envopt CPP
-envopt CFLAGS
-envopt CXXFLAGS
-envopt LDFLAGS
-
-# a little post-processing of various config values
-CFG_PREFIX=${CFG_PREFIX%/}
-CFG_MANDIR=${CFG_MANDIR%/}
-CFG_DOCDIR=${CFG_DOCDIR%/}
-CFG_BINDIR=${CFG_BINDIR%/}
-CFG_HOST="$(echo $CFG_HOST | tr ',' ' ')"
-CFG_TARGET="$(echo $CFG_TARGET | tr ',' ' ')"
-
-# copy build-triples to host-triples so that builds are a subset of hosts
-V_TEMP=""
-for i in $CFG_BUILD $CFG_HOST;
-do
-   echo "$V_TEMP" | grep -qF $i || V_TEMP="$V_TEMP${V_TEMP:+ }$i"
-done
-CFG_HOST=$V_TEMP
-
-# copy host-triples to target-triples so that hosts are a subset of targets
-V_TEMP=""
-for i in $CFG_HOST $CFG_TARGET;
-do
-   echo "$V_TEMP" | grep -qF $i || V_TEMP="$V_TEMP${V_TEMP:+ }$i"
-done
-CFG_TARGET=$V_TEMP
-
-step_msg "writing configuration"
-
-putvar CFG_SRC_DIR
-putvar CFG_SRC_DIR_RELATIVE
-putvar CFG_BUILD_DIR
-putvar CFG_OSTYPE
-putvar CFG_CPUTYPE
-putvar CFG_CONFIGURE_ARGS
-putvar CFG_PREFIX
-putvar CFG_HOST
-putvar CFG_TARGET
-putvar CFG_LIBDIR_RELATIVE
-putvar CFG_DISABLE_MANAGE_SUBMODULES
-putvar CFG_AARCH64_LINUX_ANDROID_NDK
-putvar CFG_ARM_LINUX_ANDROIDEABI_NDK
-putvar CFG_ARMV7_LINUX_ANDROIDEABI_NDK
-putvar CFG_I686_LINUX_ANDROID_NDK
-putvar CFG_X86_64_LINUX_ANDROID_NDK
-putvar CFG_NACL_CROSS_PATH
-putvar CFG_MANDIR
-putvar CFG_DOCDIR
-putvar CFG_BINDIR
-putvar CFG_USING_LIBCPP
-
-msg
-copy_if_changed ${CFG_SRC_DIR}src/bootstrap/mk/Makefile.in ./Makefile
-move_if_changed config.tmp config.mk
-rm -f config.tmp
-touch config.stamp
-
-if [ -z "$CFG_ENABLE_DEBUG" ]; then
-    step_msg "configured in release mode. for development consider --enable-debug"
-else
-    step_msg "complete"
-fi
-
-if [ "$CFG_SRC_DIR" = `pwd` ]; then
-    X_PY=x.py
-else
-    X_PY=${CFG_SRC_DIR_RELATIVE}x.py
-fi
-
-msg "run \`python ${X_PY} --help\`"
-msg
+try python2.7 "$@"
+try python27 "$@"
+try python2 "$@"
+exec python $script "$@"
diff --git a/src/Cargo.lock b/src/Cargo.lock
index 123c884585c19..b5e292159638f 100644
--- a/src/Cargo.lock
+++ b/src/Cargo.lock
@@ -80,7 +80,7 @@ version = "0.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "kernel32-sys 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.29 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.30 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -93,7 +93,7 @@ dependencies = [
  "cfg-if 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "dbghelp-sys 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "kernel32-sys 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.29 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.30 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-demangle 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -104,7 +104,7 @@ version = "0.1.12"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "gcc 0.3.51 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.29 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.30 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -140,7 +140,7 @@ dependencies = [
  "gcc 0.3.51 (registry+https://github.com/rust-lang/crates.io-index)",
  "getopts 0.2.14 (registry+https://github.com/rust-lang/crates.io-index)",
  "lazy_static 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.29 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.30 (registry+https://github.com/rust-lang/crates.io-index)",
  "num_cpus 1.6.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.11 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_derive 1.0.11 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -175,20 +175,14 @@ dependencies = [
 
 [[package]]
 name = "cargo"
-version = "0.22.0"
-source = "git+https://github.com/rust-lang/cargo#bcf3997b1fa177afc5b6c632a6fbbf6cc75df427"
-replace = "cargo 0.22.0"
-
-[[package]]
-name = "cargo"
-version = "0.22.0"
+version = "0.23.0"
 dependencies = [
  "advapi32-sys 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "atty 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "bufstream 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "cargotest 0.1.0",
  "core-foundation 0.4.4 (registry+https://github.com/rust-lang/crates.io-index)",
- "crates-io 0.11.0",
+ "crates-io 0.12.0",
  "crossbeam 0.2.10 (registry+https://github.com/rust-lang/crates.io-index)",
  "curl 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "docopt 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -197,7 +191,7 @@ dependencies = [
  "filetime 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
  "flate2 0.2.19 (registry+https://github.com/rust-lang/crates.io-index)",
  "fs2 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "git2 0.6.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "git2 0.6.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "git2-curl 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "glob 0.2.11 (registry+https://github.com/rust-lang/crates.io-index)",
  "hamcrest 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -206,8 +200,8 @@ dependencies = [
  "ignore 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "jobserver 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "kernel32-sys 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.29 (registry+https://github.com/rust-lang/crates.io-index)",
- "libgit2-sys 0.6.12 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.30 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libgit2-sys 0.6.14 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "miow 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "num_cpus 1.6.2 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -223,7 +217,7 @@ dependencies = [
  "shell-escape 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "tar 0.4.13 (registry+https://github.com/rust-lang/crates.io-index)",
  "tempdir 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)",
- "termcolor 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "termcolor 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "toml 0.4.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "url 1.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -233,10 +227,10 @@ dependencies = [
 name = "cargotest"
 version = "0.1.0"
 dependencies = [
- "cargo 0.22.0",
+ "cargo 0.23.0",
  "filetime 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
  "flate2 0.2.19 (registry+https://github.com/rust-lang/crates.io-index)",
- "git2 0.6.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "git2 0.6.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "hamcrest 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "hex 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -303,7 +297,7 @@ dependencies = [
  "env_logger 0.4.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "filetime 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
  "getopts 0.2.14 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.29 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.30 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-serialize 0.3.24 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -312,6 +306,14 @@ dependencies = [
 name = "completion"
 version = "0.1.0"
 
+[[package]]
+name = "conv"
+version = "0.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "custom_derive 0.1.7 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "core"
 version = "0.0.0"
@@ -325,7 +327,7 @@ version = "0.4.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "core-foundation-sys 0.4.4 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.29 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.30 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -333,12 +335,12 @@ name = "core-foundation-sys"
 version = "0.4.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.29 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.30 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "crates-io"
-version = "0.11.0"
+version = "0.12.0"
 dependencies = [
  "curl 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "error-chain 0.11.0-rc.2 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -353,13 +355,37 @@ name = "crossbeam"
 version = "0.2.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "cssparser"
+version = "0.13.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "cssparser-macros 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "matches 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "phf 0.7.21 (registry+https://github.com/rust-lang/crates.io-index)",
+ "procedural-masquerade 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 0.3.15 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 0.11.11 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "cssparser-macros"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "phf_codegen 0.7.21 (registry+https://github.com/rust-lang/crates.io-index)",
+ "procedural-masquerade 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 0.3.15 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 0.11.11 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "curl"
 version = "0.4.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "curl-sys 0.3.14 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.29 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.30 (registry+https://github.com/rust-lang/crates.io-index)",
  "openssl-probe 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "openssl-sys 0.9.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "socket2 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -372,7 +398,7 @@ version = "0.3.14"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "gcc 0.3.51 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.29 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.30 (registry+https://github.com/rust-lang/crates.io-index)",
  "libz-sys 1.0.16 (registry+https://github.com/rust-lang/crates.io-index)",
  "openssl-sys 0.9.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "pkg-config 0.3.9 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -380,6 +406,11 @@ dependencies = [
  "winapi 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "custom_derive"
+version = "0.1.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "dbghelp-sys"
 version = "0.2.0"
@@ -389,6 +420,14 @@ dependencies = [
  "winapi-build 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "debug_unreachable"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "unreachable 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "derive-new"
 version = "0.3.0"
@@ -417,7 +456,7 @@ dependencies = [
 
 [[package]]
 name = "dtoa"
-version = "0.4.1"
+version = "0.4.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
@@ -474,7 +513,7 @@ name = "filetime"
 version = "0.1.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.29 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.30 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -494,7 +533,7 @@ name = "flate2"
 version = "0.2.19"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.29 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.30 (registry+https://github.com/rust-lang/crates.io-index)",
  "miniz-sys 0.1.9 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -518,13 +557,22 @@ version = "0.4.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "kernel32-sys 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.29 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.30 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "futf"
+version = "0.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "debug_unreachable 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "mac 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "futures"
-version = "0.1.14"
+version = "0.1.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
@@ -539,12 +587,12 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "git2"
-version = "0.6.6"
+version = "0.6.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "bitflags 0.9.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.29 (registry+https://github.com/rust-lang/crates.io-index)",
- "libgit2-sys 0.6.12 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.30 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libgit2-sys 0.6.14 (registry+https://github.com/rust-lang/crates.io-index)",
  "openssl-probe 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "openssl-sys 0.9.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "url 1.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -556,7 +604,7 @@ version = "0.7.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "curl 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "git2 0.6.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "git2 0.6.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "url 1.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -634,6 +682,26 @@ dependencies = [
 name = "hover"
 version = "0.1.0"
 
+[[package]]
+name = "html-diff"
+version = "0.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "kuchiki 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "html5ever"
+version = "0.18.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "log 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
+ "mac 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "markup5ever 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 0.3.15 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 0.11.11 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "idna"
 version = "0.1.4"
@@ -688,7 +756,7 @@ dependencies = [
 
 [[package]]
 name = "itoa"
-version = "0.3.1"
+version = "0.3.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
@@ -696,8 +764,8 @@ name = "jobserver"
 version = "0.1.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.29 (registry+https://github.com/rust-lang/crates.io-index)",
- "rand 0.3.15 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.30 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand 0.3.16 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -705,7 +773,7 @@ name = "jsonrpc-core"
 version = "7.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "futures 0.1.14 (registry+https://github.com/rust-lang/crates.io-index)",
+ "futures 0.1.15 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.11 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_derive 1.0.11 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -721,6 +789,17 @@ dependencies = [
  "winapi-build 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "kuchiki"
+version = "0.5.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "cssparser 0.13.7 (registry+https://github.com/rust-lang/crates.io-index)",
+ "html5ever 0.18.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "matches 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "selectors 0.18.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "languageserver-types"
 version = "0.12.0"
@@ -748,18 +827,18 @@ dependencies = [
 
 [[package]]
 name = "libc"
-version = "0.2.29"
+version = "0.2.30"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "libgit2-sys"
-version = "0.6.12"
+version = "0.6.14"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "cmake 0.1.24 (registry+https://github.com/rust-lang/crates.io-index)",
  "curl-sys 0.3.14 (registry+https://github.com/rust-lang/crates.io-index)",
  "gcc 0.3.51 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.29 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.30 (registry+https://github.com/rust-lang/crates.io-index)",
  "libssh2-sys 0.2.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "libz-sys 1.0.16 (registry+https://github.com/rust-lang/crates.io-index)",
  "openssl-sys 0.9.17 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -772,7 +851,7 @@ version = "0.2.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "cmake 0.1.24 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.29 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.30 (registry+https://github.com/rust-lang/crates.io-index)",
  "libz-sys 1.0.16 (registry+https://github.com/rust-lang/crates.io-index)",
  "openssl-sys 0.9.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "pkg-config 0.3.9 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -784,7 +863,7 @@ version = "1.0.16"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "gcc 0.3.51 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.29 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.30 (registry+https://github.com/rust-lang/crates.io-index)",
  "pkg-config 0.3.9 (registry+https://github.com/rust-lang/crates.io-index)",
  "vcpkg 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -805,7 +884,42 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "filetime 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
  "gcc 0.3.51 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.29 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.30 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "mac"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[[package]]
+name = "magenta"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "conv 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "magenta-sys 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "magenta-sys"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "bitflags 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "markup5ever"
+version = "0.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "phf 0.7.21 (registry+https://github.com/rust-lang/crates.io-index)",
+ "phf_codegen 0.7.21 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rustc-serialize 0.3.24 (registry+https://github.com/rust-lang/crates.io-index)",
+ "string_cache 0.6.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "string_cache_codegen 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "tendril 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -835,7 +949,7 @@ name = "memchr"
 version = "0.1.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.29 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.30 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -843,7 +957,7 @@ name = "memchr"
 version = "1.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.29 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.30 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -852,7 +966,7 @@ version = "0.1.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "gcc 0.3.51 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.29 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.30 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -877,7 +991,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "cfg-if 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "kernel32-sys 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.29 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.30 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "ws2_32-sys 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -902,7 +1016,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "num-integer 0.1.35 (registry+https://github.com/rust-lang/crates.io-index)",
  "num-traits 0.1.40 (registry+https://github.com/rust-lang/crates.io-index)",
- "rand 0.3.15 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand 0.3.16 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-serialize 0.3.24 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -953,7 +1067,7 @@ name = "num_cpus"
 version = "1.6.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.29 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.30 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -973,7 +1087,7 @@ dependencies = [
  "bitflags 0.9.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "foreign-types 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "lazy_static 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.29 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.30 (registry+https://github.com/rust-lang/crates.io-index)",
  "openssl-sys 0.9.17 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -988,7 +1102,7 @@ version = "0.9.17"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "gcc 0.3.51 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.29 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.30 (registry+https://github.com/rust-lang/crates.io-index)",
  "pkg-config 0.3.9 (registry+https://github.com/rust-lang/crates.io-index)",
  "vcpkg 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -1029,19 +1143,64 @@ name = "pest"
 version = "0.3.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "phf"
+version = "0.7.21"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "phf_shared 0.7.21 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "phf_codegen"
+version = "0.7.21"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "phf_generator 0.7.21 (registry+https://github.com/rust-lang/crates.io-index)",
+ "phf_shared 0.7.21 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "phf_generator"
+version = "0.7.21"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "phf_shared 0.7.21 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand 0.3.16 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "phf_shared"
+version = "0.7.21"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "siphasher 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "pkg-config"
 version = "0.3.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "precomputed-hash"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "proc_macro"
 version = "0.0.0"
 dependencies = [
+ "rustc_errors 0.0.0",
  "syntax 0.0.0",
  "syntax_pos 0.0.0",
 ]
 
+[[package]]
+name = "procedural-masquerade"
+version = "0.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "profiler_builtins"
 version = "0.0.0"
@@ -1106,10 +1265,11 @@ dependencies = [
 
 [[package]]
 name = "rand"
-version = "0.3.15"
+version = "0.3.16"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.29 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.30 (registry+https://github.com/rust-lang/crates.io-index)",
+ "magenta 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1168,9 +1328,9 @@ version = "0.1.0"
 
 [[package]]
 name = "rls"
-version = "0.1.0"
+version = "0.122.0"
 dependencies = [
- "cargo 0.22.0 (git+https://github.com/rust-lang/cargo)",
+ "cargo 0.23.0",
  "env_logger 0.4.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "jsonrpc-core 7.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "languageserver-types 0.12.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1179,15 +1339,14 @@ dependencies = [
  "racer 2.0.10 (registry+https://github.com/rust-lang/crates.io-index)",
  "rls-analysis 0.6.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "rls-data 0.10.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rls-rustc 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "rls-span 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "rls-vfs 0.4.4 (registry+https://github.com/rust-lang/crates.io-index)",
- "rustfmt-nightly 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rustfmt-nightly 0.2.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.11 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_derive 1.0.11 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_json 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "toml 0.4.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "url 1.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "url_serde 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1213,6 +1372,11 @@ dependencies = [
  "serde_derive 1.0.11 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "rls-rustc"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "rls-span"
 version = "0.4.0"
@@ -1634,6 +1798,7 @@ dependencies = [
  "build_helper 0.1.0",
  "env_logger 0.4.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "gcc 0.3.51 (registry+https://github.com/rust-lang/crates.io-index)",
+ "html-diff 0.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "pulldown-cmark 0.0.14 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -1647,14 +1812,14 @@ dependencies = [
 
 [[package]]
 name = "rustfmt-nightly"
-version = "0.2.2"
+version = "0.2.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "diff 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
  "env_logger 0.4.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "getopts 0.2.14 (registry+https://github.com/rust-lang/crates.io-index)",
  "kernel32-sys 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.29 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.30 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "regex 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.11 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1686,6 +1851,21 @@ name = "scopeguard"
 version = "0.1.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "selectors"
+version = "0.18.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "bitflags 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cssparser 0.13.7 (registry+https://github.com/rust-lang/crates.io-index)",
+ "fnv 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)",
+ "matches 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "phf 0.7.21 (registry+https://github.com/rust-lang/crates.io-index)",
+ "phf_codegen 0.7.21 (registry+https://github.com/rust-lang/crates.io-index)",
+ "precomputed-hash 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "smallvec 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "semver"
 version = "0.7.0"
@@ -1737,8 +1917,8 @@ name = "serde_json"
 version = "1.0.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "dtoa 0.4.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "itoa 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "dtoa 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "itoa 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "num-traits 0.1.40 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.11 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -1752,6 +1932,16 @@ name = "shell-escape"
 version = "0.1.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "siphasher"
+version = "0.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[[package]]
+name = "smallvec"
+version = "0.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "socket2"
 version = "0.2.2"
@@ -1759,7 +1949,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "cfg-if 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "kernel32-sys 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.29 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.30 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "ws2_32-sys 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -1801,6 +1991,36 @@ dependencies = [
  "core 0.0.0",
 ]
 
+[[package]]
+name = "string_cache"
+version = "0.6.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "debug_unreachable 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "lazy_static 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
+ "phf_shared 0.7.21 (registry+https://github.com/rust-lang/crates.io-index)",
+ "precomputed-hash 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.11 (registry+https://github.com/rust-lang/crates.io-index)",
+ "string_cache_codegen 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "string_cache_shared 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "string_cache_codegen"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "phf_generator 0.7.21 (registry+https://github.com/rust-lang/crates.io-index)",
+ "phf_shared 0.7.21 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 0.3.15 (registry+https://github.com/rust-lang/crates.io-index)",
+ "string_cache_shared 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "string_cache_shared"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "strings"
 version = "0.1.0"
@@ -1877,7 +2097,7 @@ name = "syntex_errors"
 version = "0.52.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.29 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.30 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-serialize 0.3.24 (registry+https://github.com/rust-lang/crates.io-index)",
  "syntex_pos 0.52.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1899,7 +2119,7 @@ version = "0.52.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "bitflags 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.29 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.30 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-serialize 0.3.24 (registry+https://github.com/rust-lang/crates.io-index)",
  "syntex_errors 0.52.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1914,7 +2134,7 @@ version = "0.4.13"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "filetime 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.29 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.30 (registry+https://github.com/rust-lang/crates.io-index)",
  "xattr 0.1.11 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -1923,7 +2143,17 @@ name = "tempdir"
 version = "0.3.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "rand 0.3.15 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand 0.3.16 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "tendril"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "futf 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "mac 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "utf-8 0.7.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1945,13 +2175,13 @@ version = "0.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "kernel32-sys 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.29 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.30 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "termcolor"
-version = "0.3.2"
+version = "0.3.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "wincolor 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1980,7 +2210,7 @@ version = "2.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "kernel32-sys 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.29 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.30 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -2058,6 +2288,14 @@ name = "unicode-xid"
 version = "0.0.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "unreachable"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "void 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "unreachable"
 version = "1.0.0"
@@ -2101,6 +2339,14 @@ dependencies = [
  "winapi-build 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "utf-8"
+version = "0.7.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "matches 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "utf8-ranges"
 version = "0.1.3"
@@ -2169,7 +2415,7 @@ name = "xattr"
 version = "0.1.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.29 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.30 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -2198,20 +2444,24 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum bitflags 0.8.2 (registry+https://github.com/rust-lang/crates.io-index)" = "1370e9fc2a6ae53aea8b7a5110edbd08836ed87c88736dfabccade1c2b44bff4"
 "checksum bitflags 0.9.1 (registry+https://github.com/rust-lang/crates.io-index)" = "4efd02e230a02e18f92fc2735f44597385ed02ad8f831e7c1c1156ee5e1ab3a5"
 "checksum bufstream 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)" = "f2f382711e76b9de6c744cc00d0497baba02fb00a787f088c879f01d09468e32"
-"checksum cargo 0.22.0 (git+https://github.com/rust-lang/cargo)" = "<none>"
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 "checksum docopt 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)" = "3b5b93718f8b3e5544fcc914c43de828ca6c6ace23e0332c6080a2977b49787a"
-"checksum dtoa 0.4.1 (registry+https://github.com/rust-lang/crates.io-index)" = "80c8b71fd71146990a9742fc06dcbbde19161a267e0ad4e572c35162f4578c90"
+"checksum dtoa 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)" = "09c3753c3db574d215cba4ea76018483895d7bff25a31b49ba45db21c48e50ab"
 "checksum enum_primitive 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "be4551092f4d519593039259a9ed8daedf0da12e5109c5280338073eaeb81180"
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@@ -2222,10 +2472,11 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum fnv 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)" = "6cc484842f1e2884faf56f529f960cc12ad8c71ce96cc7abba0a067c98fee344"
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-"checksum futures 0.1.14 (registry+https://github.com/rust-lang/crates.io-index)" = "4b63a4792d4f8f686defe3b39b92127fea6344de5d38202b2ee5a11bbbf29d6a"
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 "checksum getopts 0.2.14 (registry+https://github.com/rust-lang/crates.io-index)" = "d9047cfbd08a437050b363d35ef160452c5fe8ea5187ae0a624708c91581d685"
-"checksum git2 0.6.6 (registry+https://github.com/rust-lang/crates.io-index)" = "aa01936ac96555c083c0e8553f672616274408d9d3fc5b8696603fbf63ff43ee"
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 "checksum git2-curl 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)" = "68676bc784bf0bef83278898929bf64a251e87c0340723d0b93fa096c9c5bf8e"
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@@ -2233,20 +2484,27 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
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@@ -2269,28 +2527,36 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum owning_ref 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)" = "cdf84f41639e037b484f93433aa3897863b561ed65c6e59c7073d7c561710f37"
 "checksum percent-encoding 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "de154f638187706bde41d9b4738748933d64e6b37bdbffc0b47a97d16a6ae356"
 "checksum pest 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)" = "0a6dda33d67c26f0aac90d324ab2eb7239c819fc7b2552fe9faa4fe88441edc8"
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 "checksum regex-syntax 0.3.9 (registry+https://github.com/rust-lang/crates.io-index)" = "f9ec002c35e86791825ed294b50008eea9ddfc8def4420124fbc6b08db834957"
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-"checksum rustfmt-nightly 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "6eea0d0590ae793fc4d281df56e01dc7531575c8ed9a72fadf5fdc7305a0d32f"
+"checksum rustfmt-nightly 0.2.5 (registry+https://github.com/rust-lang/crates.io-index)" = "7d6dbb39239e54df780a850721fba87b3fdb2e645b39041742ec111369cec6af"
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 "checksum scopeguard 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)" = "59a076157c1e2dc561d8de585151ee6965d910dd4dcb5dabb7ae3e83981a6c57"
+"checksum selectors 0.18.0 (registry+https://github.com/rust-lang/crates.io-index)" = "e3c89b1c6a3c029c82263f7dd2d44d0005ee7374eb09e254ab59dede4353a8c0"
 "checksum semver 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)" = "3fdd61b85a0fa777f7fb7c454b9189b2941b110d1385ce84d7f76efdf1606a85"
 "checksum semver-parser 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)" = "388a1df253eca08550bef6c72392cfe7c30914bf41df5269b68cbd6ff8f570a3"
 "checksum serde 1.0.11 (registry+https://github.com/rust-lang/crates.io-index)" = "f7726f29ddf9731b17ff113c461e362c381d9d69433f79de4f3dd572488823e9"
@@ -2299,8 +2565,13 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum serde_ignored 0.0.3 (registry+https://github.com/rust-lang/crates.io-index)" = "c10e798e4405d7dcec3658989e35ee6706f730a9ed7c1184d5ebd84317e82f46"
 "checksum serde_json 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)" = "48b04779552e92037212c3615370f6bd57a40ebba7f20e554ff9f55e41a69a7b"
 "checksum shell-escape 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)" = "dd5cc96481d54583947bfe88bf30c23d53f883c6cd0145368b69989d97b84ef8"
+"checksum siphasher 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "0df90a788073e8d0235a67e50441d47db7c8ad9debd91cbf43736a2a92d36537"
+"checksum smallvec 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)" = "4f8266519bc1d17d0b5b16f6c21295625d562841c708f6376f49028a43e9c11e"
 "checksum socket2 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "4daf80fcf54186fac4fe049e0b39d36a5cfde69a11a06413e61e77f553cccf9a"
 "checksum stable_deref_trait 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "15132e0e364248108c5e2c02e3ab539be8d6f5d52a01ca9bbf27ed657316f02b"
+"checksum string_cache 0.6.2 (registry+https://github.com/rust-lang/crates.io-index)" = "413fc7852aeeb5472f1986ef755f561ddf0c789d3d796e65f0b6fe293ecd4ef8"
+"checksum string_cache_codegen 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "479cde50c3539481f33906a387f2bd17c8e87cb848c35b6021d41fb81ff9b4d7"
+"checksum string_cache_shared 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "b1884d1bc09741d466d9b14e6d37ac89d6909cbcac41dd9ae982d4d063bbedfc"
 "checksum strings 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "da75d8bf2c4d210d63dd09581a041b036001f9f6e03d9b151dbff810fb7ba26a"
 "checksum strsim 0.6.0 (registry+https://github.com/rust-lang/crates.io-index)" = "b4d15c810519a91cf877e7e36e63fe068815c678181439f2f29e2562147c3694"
 "checksum syn 0.11.11 (registry+https://github.com/rust-lang/crates.io-index)" = "d3b891b9015c88c576343b9b3e41c2c11a51c219ef067b264bd9c8aa9b441dad"
@@ -2311,9 +2582,10 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum syntex_syntax 0.52.0 (registry+https://github.com/rust-lang/crates.io-index)" = "76a302e717e348aa372ff577791c3832395650073b8d8432f8b3cb170b34afde"
 "checksum tar 0.4.13 (registry+https://github.com/rust-lang/crates.io-index)" = "281285b717926caa919ad905ef89c63d75805c7d89437fb873100925a53f2b1b"
 "checksum tempdir 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)" = "87974a6f5c1dfb344d733055601650059a3363de2a6104819293baff662132d6"
+"checksum tendril 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)" = "8c1b72f8e2f5b73b65c315b1a70c730f24b9d7a25f39e98de8acbe2bb795caea"
 "checksum term 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)" = "fa63644f74ce96fbeb9b794f66aff2a52d601cbd5e80f4b97123e3899f4570f1"
 "checksum term_size 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "e2b6b55df3198cc93372e85dd2ed817f0e38ce8cc0f22eb32391bfad9c4bf209"
-"checksum termcolor 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)" = "9a5193a56b8d82014662c4b933dea6bec851daf018a2b01722e007daaf5f9dca"
+"checksum termcolor 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)" = "9065bced9c3e43453aa3d56f1e98590b8455b341d2fa191a1090c0dd0b242c75"
 "checksum textwrap 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)" = "f728584ea33b0ad19318e20557cb0a39097751dbb07171419673502f848c7af6"
 "checksum thread-id 2.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "a9539db560102d1cef46b8b78ce737ff0bb64e7e18d35b2a5688f7d097d0ff03"
 "checksum thread_local 0.2.7 (registry+https://github.com/rust-lang/crates.io-index)" = "8576dbbfcaef9641452d5cf0df9b0e7eeab7694956dd33bb61515fb8f18cfdd5"
@@ -2327,10 +2599,12 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum unicode-width 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)" = "bf3a113775714a22dcb774d8ea3655c53a32debae63a063acc00a91cc586245f"
 "checksum unicode-xid 0.0.3 (registry+https://github.com/rust-lang/crates.io-index)" = "36dff09cafb4ec7c8cf0023eb0b686cb6ce65499116a12201c9e11840ca01beb"
 "checksum unicode-xid 0.0.4 (registry+https://github.com/rust-lang/crates.io-index)" = "8c1f860d7d29cf02cb2f3f359fd35991af3d30bac52c57d265a3c461074cb4dc"
+"checksum unreachable 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "1f2ae5ddb18e1c92664717616dd9549dde73f539f01bd7b77c2edb2446bdff91"
 "checksum unreachable 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "382810877fe448991dfc7f0dd6e3ae5d58088fd0ea5e35189655f84e6814fa56"
 "checksum url 1.5.1 (registry+https://github.com/rust-lang/crates.io-index)" = "eeb819346883532a271eb626deb43c4a1bb4c4dd47c519bd78137c3e72a4fe27"
 "checksum url_serde 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "74e7d099f1ee52f823d4bdd60c93c3602043c728f5db3b97bdb548467f7bddea"
 "checksum userenv-sys 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "71d28ea36bbd9192d75bd9fa9b39f96ddb986eaee824adae5d53b6e51919b2f3"
+"checksum utf-8 0.7.1 (registry+https://github.com/rust-lang/crates.io-index)" = "b6f923c601c7ac48ef1d66f7d5b5b2d9a7ba9c51333ab75a3ddf8d0309185a56"
 "checksum utf8-ranges 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)" = "a1ca13c08c41c9c3e04224ed9ff80461d97e121589ff27c753a16cb10830ae0f"
 "checksum utf8-ranges 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "662fab6525a98beff2921d7f61a39e7d59e0b425ebc7d0d9e66d316e55124122"
 "checksum vcpkg 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "9e0a7d8bed3178a8fb112199d466eeca9ed09a14ba8ad67718179b4fd5487d0b"
diff --git a/src/Cargo.toml b/src/Cargo.toml
index ffec3eb075500..35ba022c4899a 100644
--- a/src/Cargo.toml
+++ b/src/Cargo.toml
@@ -56,5 +56,5 @@ debug-assertions = false
 debug = false
 debug-assertions = false
 
-[replace]
-"https://github.com/rust-lang/cargo#0.22.0" = { path = "tools/cargo" }
+[patch.'https://github.com/rust-lang/cargo']
+cargo = { path = "tools/cargo" }
diff --git a/src/bootstrap/README.md b/src/bootstrap/README.md
index 2e844ceb17831..e543b8c070bcc 100644
--- a/src/bootstrap/README.md
+++ b/src/bootstrap/README.md
@@ -76,10 +76,9 @@ The script accepts commands, flags, and arguments to determine what to do:
 There are currently two methods for configuring the rustbuild build system.
 
 First, rustbuild offers a TOML-based configuration system with a `config.toml`
-file in the same location as `config.mk`. An example of this configuration can
-be found at `config.toml.example`, and the configuration file can also be passed
-as `--config path/to/config.toml` if the build system is being invoked manually
-(via the python script).
+file. An example of this configuration can be found at `config.toml.example`,
+and the configuration file can also be passed as `--config path/to/config.toml`
+if the build system is being invoked manually (via the python script).
 
 Next, the `./configure` options serialized in `config.mk` will be
 parsed and read. That is, if any `./configure` options are passed, they'll be
diff --git a/src/bootstrap/bootstrap.py b/src/bootstrap/bootstrap.py
index 9369a55ccb97b..4ef6d70e820ea 100644
--- a/src/bootstrap/bootstrap.py
+++ b/src/bootstrap/bootstrap.py
@@ -167,6 +167,141 @@ def format_build_time(duration):
     return str(datetime.timedelta(seconds=int(duration)))
 
 
+def default_build_triple():
+    """Build triple as in LLVM"""
+    default_encoding = sys.getdefaultencoding()
+    try:
+        ostype = subprocess.check_output(
+            ['uname', '-s']).strip().decode(default_encoding)
+        cputype = subprocess.check_output(
+            ['uname', '-m']).strip().decode(default_encoding)
+    except (subprocess.CalledProcessError, OSError):
+        if sys.platform == 'win32':
+            return 'x86_64-pc-windows-msvc'
+        err = "uname not found"
+        sys.exit(err)
+
+    # The goal here is to come up with the same triple as LLVM would,
+    # at least for the subset of platforms we're willing to target.
+    ostype_mapper = {
+        'Bitrig': 'unknown-bitrig',
+        'Darwin': 'apple-darwin',
+        'DragonFly': 'unknown-dragonfly',
+        'FreeBSD': 'unknown-freebsd',
+        'Haiku': 'unknown-haiku',
+        'NetBSD': 'unknown-netbsd',
+        'OpenBSD': 'unknown-openbsd'
+    }
+
+    # Consider the direct transformation first and then the special cases
+    if ostype in ostype_mapper:
+        ostype = ostype_mapper[ostype]
+    elif ostype == 'Linux':
+        os_from_sp = subprocess.check_output(
+            ['uname', '-o']).strip().decode(default_encoding)
+        if os_from_sp == 'Android':
+            ostype = 'linux-android'
+        else:
+            ostype = 'unknown-linux-gnu'
+    elif ostype == 'SunOS':
+        ostype = 'sun-solaris'
+        # On Solaris, uname -m will return a machine classification instead
+        # of a cpu type, so uname -p is recommended instead.  However, the
+        # output from that option is too generic for our purposes (it will
+        # always emit 'i386' on x86/amd64 systems).  As such, isainfo -k
+        # must be used instead.
+        try:
+            cputype = subprocess.check_output(
+                ['isainfo', '-k']).strip().decode(default_encoding)
+        except (subprocess.CalledProcessError, OSError):
+            err = "isainfo not found"
+            sys.exit(err)
+    elif ostype.startswith('MINGW'):
+        # msys' `uname` does not print gcc configuration, but prints msys
+        # configuration. so we cannot believe `uname -m`:
+        # msys1 is always i686 and msys2 is always x86_64.
+        # instead, msys defines $MSYSTEM which is MINGW32 on i686 and
+        # MINGW64 on x86_64.
+        ostype = 'pc-windows-gnu'
+        cputype = 'i686'
+        if os.environ.get('MSYSTEM') == 'MINGW64':
+            cputype = 'x86_64'
+    elif ostype.startswith('MSYS'):
+        ostype = 'pc-windows-gnu'
+    elif ostype.startswith('CYGWIN_NT'):
+        cputype = 'i686'
+        if ostype.endswith('WOW64'):
+            cputype = 'x86_64'
+        ostype = 'pc-windows-gnu'
+    else:
+        err = "unknown OS type: {}".format(ostype)
+        sys.exit(err)
+
+    cputype_mapper = {
+        'BePC': 'i686',
+        'aarch64': 'aarch64',
+        'amd64': 'x86_64',
+        'arm64': 'aarch64',
+        'i386': 'i686',
+        'i486': 'i686',
+        'i686': 'i686',
+        'i786': 'i686',
+        'powerpc': 'powerpc',
+        'powerpc64': 'powerpc64',
+        'powerpc64le': 'powerpc64le',
+        'ppc': 'powerpc',
+        'ppc64': 'powerpc64',
+        'ppc64le': 'powerpc64le',
+        's390x': 's390x',
+        'x64': 'x86_64',
+        'x86': 'i686',
+        'x86-64': 'x86_64',
+        'x86_64': 'x86_64'
+    }
+
+    # Consider the direct transformation first and then the special cases
+    if cputype in cputype_mapper:
+        cputype = cputype_mapper[cputype]
+    elif cputype in {'xscale', 'arm'}:
+        cputype = 'arm'
+        if ostype == 'linux-android':
+            ostype = 'linux-androideabi'
+    elif cputype == 'armv6l':
+        cputype = 'arm'
+        if ostype == 'linux-android':
+            ostype = 'linux-androideabi'
+        else:
+            ostype += 'eabihf'
+    elif cputype in {'armv7l', 'armv8l'}:
+        cputype = 'armv7'
+        if ostype == 'linux-android':
+            ostype = 'linux-androideabi'
+        else:
+            ostype += 'eabihf'
+    elif cputype == 'mips':
+        if sys.byteorder == 'big':
+            cputype = 'mips'
+        elif sys.byteorder == 'little':
+            cputype = 'mipsel'
+        else:
+            raise ValueError("unknown byteorder: {}".format(sys.byteorder))
+    elif cputype == 'mips64':
+        if sys.byteorder == 'big':
+            cputype = 'mips64'
+        elif sys.byteorder == 'little':
+            cputype = 'mips64el'
+        else:
+            raise ValueError('unknown byteorder: {}'.format(sys.byteorder))
+        # only the n64 ABI is supported, indicate it
+        ostype += 'abi64'
+    elif cputype == 'sparcv9':
+        pass
+    else:
+        err = "unknown cpu type: {}".format(cputype)
+        sys.exit(err)
+
+    return "{}-{}".format(cputype, ostype)
+
 class RustBuild(object):
     """Provide all the methods required to build Rust"""
     def __init__(self):
@@ -177,7 +312,6 @@ def __init__(self):
         self.build = ''
         self.build_dir = os.path.join(os.getcwd(), "build")
         self.clean = False
-        self.config_mk = ''
         self.config_toml = ''
         self.printed = False
         self.rust_root = os.path.abspath(os.path.join(__file__, '../../..'))
@@ -374,26 +508,6 @@ def get_toml(self, key):
                 return self.get_string(value) or value.strip()
         return None
 
-    def get_mk(self, key):
-        """Returns the value of the given key in config.mk, otherwise returns None
-
-        >>> rb = RustBuild()
-        >>> rb.config_mk = 'key := value\\n'
-        >>> rb.get_mk('key')
-        'value'
-
-        If the key does not exists, the result is None:
-
-        >>> rb.get_mk('does_not_exists') == None
-        True
-        """
-        for line in iter(self.config_mk.splitlines()):
-            if line.startswith(key + ' '):
-                var = line[line.find(':=') + 2:].strip()
-                if var != '':
-                    return var
-        return None
-
     def cargo(self):
         """Return config path for cargo"""
         return self.program_config('cargo')
@@ -407,15 +521,9 @@ def program_config(self, program):
 
         >>> rb = RustBuild()
         >>> rb.config_toml = 'rustc = "rustc"\\n'
-        >>> rb.config_mk = 'CFG_LOCAL_RUST_ROOT := /tmp/rust\\n'
         >>> rb.program_config('rustc')
         'rustc'
-        >>> cargo_path = rb.program_config('cargo')
-        >>> cargo_path.rstrip(".exe") == os.path.join("/tmp/rust",
-        ... "bin", "cargo")
-        True
         >>> rb.config_toml = ''
-        >>> rb.config_mk = ''
         >>> cargo_path = rb.program_config('cargo')
         >>> cargo_path.rstrip(".exe") == os.path.join(rb.bin_root(),
         ... "bin", "cargo")
@@ -424,10 +532,6 @@ def program_config(self, program):
         config = self.get_toml(program)
         if config:
             return config
-        config = self.get_mk('CFG_LOCAL_RUST_ROOT')
-        if config:
-            return os.path.join(config, "bin", "{}{}".format(
-                program, self.exe_suffix()))
         return os.path.join(self.bin_root(), "bin", "{}{}".format(
             program, self.exe_suffix()))
 
@@ -439,10 +543,14 @@ def get_string(line):
         'devel'
         """
         start = line.find('"')
-        if start == -1:
-            return None
-        end = start + 1 + line[start + 1:].find('"')
-        return line[start + 1:end]
+        if start != -1:
+            end = start + 1 + line[start + 1:].find('"')
+            return line[start + 1:end]
+        start = line.find('\'')
+        if start != -1:
+            end = start + 1 + line[start + 1:].find('\'')
+            return line[start + 1:end]
+        return None
 
     @staticmethod
     def exe_suffix():
@@ -521,154 +629,12 @@ def build_triple(self):
         config = self.get_toml('build')
         if config:
             return config
-        config = self.get_mk('CFG_BUILD')
-        if config:
-            return config
-        try:
-            ostype = subprocess.check_output(
-                ['uname', '-s']).strip().decode(default_encoding)
-            cputype = subprocess.check_output(
-                ['uname', '-m']).strip().decode(default_encoding)
-        except (subprocess.CalledProcessError, OSError):
-            if sys.platform == 'win32':
-                return 'x86_64-pc-windows-msvc'
-            err = "uname not found"
-            if self.verbose:
-                raise Exception(err)
-            sys.exit(err)
-
-        # The goal here is to come up with the same triple as LLVM would,
-        # at least for the subset of platforms we're willing to target.
-        ostype_mapper = {
-            'Bitrig': 'unknown-bitrig',
-            'Darwin': 'apple-darwin',
-            'DragonFly': 'unknown-dragonfly',
-            'FreeBSD': 'unknown-freebsd',
-            'Haiku': 'unknown-haiku',
-            'NetBSD': 'unknown-netbsd',
-            'OpenBSD': 'unknown-openbsd'
-        }
-
-        # Consider the direct transformation first and then the special cases
-        if ostype in ostype_mapper:
-            ostype = ostype_mapper[ostype]
-        elif ostype == 'Linux':
-            os_from_sp = subprocess.check_output(
-                ['uname', '-o']).strip().decode(default_encoding)
-            if os_from_sp == 'Android':
-                ostype = 'linux-android'
-            else:
-                ostype = 'unknown-linux-gnu'
-        elif ostype == 'SunOS':
-            ostype = 'sun-solaris'
-            # On Solaris, uname -m will return a machine classification instead
-            # of a cpu type, so uname -p is recommended instead.  However, the
-            # output from that option is too generic for our purposes (it will
-            # always emit 'i386' on x86/amd64 systems).  As such, isainfo -k
-            # must be used instead.
-            try:
-                cputype = subprocess.check_output(
-                    ['isainfo', '-k']).strip().decode(default_encoding)
-            except (subprocess.CalledProcessError, OSError):
-                err = "isainfo not found"
-                if self.verbose:
-                    raise Exception(err)
-                sys.exit(err)
-        elif ostype.startswith('MINGW'):
-            # msys' `uname` does not print gcc configuration, but prints msys
-            # configuration. so we cannot believe `uname -m`:
-            # msys1 is always i686 and msys2 is always x86_64.
-            # instead, msys defines $MSYSTEM which is MINGW32 on i686 and
-            # MINGW64 on x86_64.
-            ostype = 'pc-windows-gnu'
-            cputype = 'i686'
-            if os.environ.get('MSYSTEM') == 'MINGW64':
-                cputype = 'x86_64'
-        elif ostype.startswith('MSYS'):
-            ostype = 'pc-windows-gnu'
-        elif ostype.startswith('CYGWIN_NT'):
-            cputype = 'i686'
-            if ostype.endswith('WOW64'):
-                cputype = 'x86_64'
-            ostype = 'pc-windows-gnu'
-        else:
-            err = "unknown OS type: {}".format(ostype)
-            if self.verbose:
-                raise ValueError(err)
-            sys.exit(err)
-
-        cputype_mapper = {
-            'BePC': 'i686',
-            'aarch64': 'aarch64',
-            'amd64': 'x86_64',
-            'arm64': 'aarch64',
-            'i386': 'i686',
-            'i486': 'i686',
-            'i686': 'i686',
-            'i786': 'i686',
-            'powerpc': 'powerpc',
-            'powerpc64': 'powerpc64',
-            'powerpc64le': 'powerpc64le',
-            'ppc': 'powerpc',
-            'ppc64': 'powerpc64',
-            'ppc64le': 'powerpc64le',
-            's390x': 's390x',
-            'x64': 'x86_64',
-            'x86': 'i686',
-            'x86-64': 'x86_64',
-            'x86_64': 'x86_64'
-        }
-
-        # Consider the direct transformation first and then the special cases
-        if cputype in cputype_mapper:
-            cputype = cputype_mapper[cputype]
-        elif cputype in {'xscale', 'arm'}:
-            cputype = 'arm'
-            if ostype == 'linux-android':
-                ostype = 'linux-androideabi'
-        elif cputype == 'armv6l':
-            cputype = 'arm'
-            if ostype == 'linux-android':
-                ostype = 'linux-androideabi'
-            else:
-                ostype += 'eabihf'
-        elif cputype in {'armv7l', 'armv8l'}:
-            cputype = 'armv7'
-            if ostype == 'linux-android':
-                ostype = 'linux-androideabi'
-            else:
-                ostype += 'eabihf'
-        elif cputype == 'mips':
-            if sys.byteorder == 'big':
-                cputype = 'mips'
-            elif sys.byteorder == 'little':
-                cputype = 'mipsel'
-            else:
-                raise ValueError("unknown byteorder: {}".format(sys.byteorder))
-        elif cputype == 'mips64':
-            if sys.byteorder == 'big':
-                cputype = 'mips64'
-            elif sys.byteorder == 'little':
-                cputype = 'mips64el'
-            else:
-                raise ValueError('unknown byteorder: {}'.format(sys.byteorder))
-            # only the n64 ABI is supported, indicate it
-            ostype += 'abi64'
-        elif cputype == 'sparcv9':
-            pass
-        else:
-            err = "unknown cpu type: {}".format(cputype)
-            if self.verbose:
-                raise ValueError(err)
-            sys.exit(err)
-
-        return "{}-{}".format(cputype, ostype)
+        return default_build_triple()
 
     def update_submodules(self):
         """Update submodules"""
         if (not os.path.exists(os.path.join(self.rust_root, ".git"))) or \
-                self.get_toml('submodules') == "false" or \
-                self.get_mk('CFG_DISABLE_MANAGE_SUBMODULES') == "1":
+                self.get_toml('submodules') == "false":
             return
         print('Updating submodules')
         default_encoding = sys.getdefaultencoding()
@@ -680,11 +646,9 @@ def update_submodules(self):
         ).decode(default_encoding).splitlines()]
         submodules = [module for module in submodules
                       if not ((module.endswith("llvm") and
-                               (self.get_toml('llvm-config') or
-                                self.get_mk('CFG_LLVM_ROOT'))) or
+                               self.get_toml('llvm-config')) or
                               (module.endswith("jemalloc") and
-                               (self.get_toml('jemalloc') or
-                                self.get_mk('CFG_JEMALLOC_ROOT'))))]
+                               self.get_toml('jemalloc')))]
         run(["git", "submodule", "update",
              "--init", "--recursive"] + submodules,
             cwd=self.rust_root, verbose=self.verbose)
@@ -721,21 +685,15 @@ def bootstrap():
             build.config_toml = config.read()
     except:
         pass
-    try:
-        build.config_mk = open('config.mk').read()
-    except:
-        pass
 
     if '\nverbose = 2' in build.config_toml:
         build.verbose = 2
     elif '\nverbose = 1' in build.config_toml:
         build.verbose = 1
 
-    build.use_vendored_sources = '\nvendor = true' in build.config_toml or \
-                                 'CFG_ENABLE_VENDOR' in build.config_mk
+    build.use_vendored_sources = '\nvendor = true' in build.config_toml
 
-    build.use_locked_deps = '\nlocked-deps = true' in build.config_toml or \
-                            'CFG_ENABLE_LOCKED_DEPS' in build.config_mk
+    build.use_locked_deps = '\nlocked-deps = true' in build.config_toml
 
     if 'SUDO_USER' in os.environ and not build.use_vendored_sources:
         if os.environ.get('USER') != os.environ['SUDO_USER']:
diff --git a/src/bootstrap/bootstrap_test.py b/src/bootstrap/bootstrap_test.py
index a65a3a4042eca..32ea4b4abe638 100644
--- a/src/bootstrap/bootstrap_test.py
+++ b/src/bootstrap/bootstrap_test.py
@@ -15,6 +15,7 @@
 import unittest
 import tempfile
 import hashlib
+import sys
 
 from shutil import rmtree
 
@@ -110,5 +111,6 @@ def test_same_dates(self):
         TEST_LOADER.loadTestsFromTestCase(VerifyTestCase),
         TEST_LOADER.loadTestsFromTestCase(ProgramOutOfDate)])
 
-    RUNNER = unittest.TextTestRunner(verbosity=2)
-    RUNNER.run(SUITE)
+    RUNNER = unittest.TextTestRunner(stream=sys.stdout, verbosity=2)
+    result = RUNNER.run(SUITE)
+    sys.exit(0 if result.wasSuccessful() else 1)
diff --git a/src/bootstrap/builder.rs b/src/bootstrap/builder.rs
index 298f6a004a20a..722b3d16e9d19 100644
--- a/src/bootstrap/builder.rs
+++ b/src/bootstrap/builder.rs
@@ -248,7 +248,7 @@ impl<'a> Builder<'a> {
                 compile::StartupObjects, tool::BuildManifest, tool::Rustbook, tool::ErrorIndex,
                 tool::UnstableBookGen, tool::Tidy, tool::Linkchecker, tool::CargoTest,
                 tool::Compiletest, tool::RemoteTestServer, tool::RemoteTestClient,
-                tool::RustInstaller, tool::Cargo, tool::Rls, tool::Rustdoc,
+                tool::RustInstaller, tool::Cargo, tool::Rls, tool::Rustdoc, tool::Clippy,
                 native::Llvm),
             Kind::Test => describe!(check::Tidy, check::Bootstrap, check::DefaultCompiletest,
                 check::HostCompiletest, check::Crate, check::CrateLibrustc, check::Linkcheck,
diff --git a/src/bootstrap/channel.rs b/src/bootstrap/channel.rs
index 9c1ae83d38281..6ed504dfe74a3 100644
--- a/src/bootstrap/channel.rs
+++ b/src/bootstrap/channel.rs
@@ -24,7 +24,7 @@ use Build;
 use config::Config;
 
 // The version number
-pub const CFG_RELEASE_NUM: &str = "1.21.0";
+pub const CFG_RELEASE_NUM: &str = "1.22.0";
 
 // An optional number to put after the label, e.g. '.2' -> '-beta.2'
 // Be sure to make this starts with a dot to conform to semver pre-release
diff --git a/src/bootstrap/config.rs b/src/bootstrap/config.rs
index f43035fbfe8a1..372e0906cc61e 100644
--- a/src/bootstrap/config.rs
+++ b/src/bootstrap/config.rs
@@ -10,12 +10,12 @@
 
 //! Serialized configuration of a build.
 //!
-//! This module implements parsing `config.mk` and `config.toml` configuration
-//! files to tweak how the build runs.
+//! This module implements parsing `config.toml` configuration files to tweak
+//! how the build runs.
 
 use std::collections::HashMap;
 use std::env;
-use std::fs::{self, File};
+use std::fs::File;
 use std::io::prelude::*;
 use std::path::PathBuf;
 use std::process;
@@ -23,7 +23,7 @@ use std::cmp;
 
 use num_cpus;
 use toml;
-use util::{exe, push_exe_path};
+use util::exe;
 use cache::{INTERNER, Interned};
 use flags::Flags;
 pub use flags::Subcommand;
@@ -124,14 +124,12 @@ pub struct Config {
     pub nodejs: Option<PathBuf>,
     pub gdb: Option<PathBuf>,
     pub python: Option<PathBuf>,
-    pub configure_args: Vec<String>,
     pub openssl_static: bool,
-
+    pub configure_args: Vec<String>,
 
     // These are either the stage0 downloaded binaries or the locally installed ones.
     pub initial_cargo: PathBuf,
     pub initial_rustc: PathBuf,
-
 }
 
 /// Per-target configuration stored in the global configuration structure.
@@ -190,6 +188,8 @@ struct Build {
     sanitizers: Option<bool>,
     profiler: Option<bool>,
     openssl_static: Option<bool>,
+    configure_args: Option<Vec<String>>,
+    local_rebuild: Option<bool>,
 }
 
 /// TOML representation of various global install decisions.
@@ -219,6 +219,7 @@ struct Llvm {
     targets: Option<String>,
     experimental_targets: Option<String>,
     link_jobs: Option<u32>,
+    link_shared: Option<bool>,
 }
 
 #[derive(Deserialize, Default, Clone)]
@@ -265,6 +266,9 @@ struct Rust {
     debuginfo_tests: Option<bool>,
     codegen_tests: Option<bool>,
     ignore_git: Option<bool>,
+    debug: Option<bool>,
+    dist_src: Option<bool>,
+    quiet_tests: Option<bool>,
 }
 
 /// TOML representation of how each build target is configured.
@@ -374,6 +378,8 @@ impl Config {
         set(&mut config.sanitizers, build.sanitizers);
         set(&mut config.profiler, build.profiler);
         set(&mut config.openssl_static, build.openssl_static);
+        set(&mut config.configure_args, build.configure_args);
+        set(&mut config.local_rebuild, build.local_rebuild);
         config.verbose = cmp::max(config.verbose, flags.verbose);
 
         if let Some(ref install) = toml.install {
@@ -385,6 +391,18 @@ impl Config {
             config.mandir = install.mandir.clone().map(PathBuf::from);
         }
 
+        // Store off these values as options because if they're not provided
+        // we'll infer default values for them later
+        let mut llvm_assertions = None;
+        let mut debuginfo_lines = None;
+        let mut debuginfo_only_std = None;
+        let mut debug = None;
+        let mut debug_jemalloc = None;
+        let mut debuginfo = None;
+        let mut debug_assertions = None;
+        let mut optimize = None;
+        let mut ignore_git = None;
+
         if let Some(ref llvm) = toml.llvm {
             match llvm.ccache {
                 Some(StringOrBool::String(ref s)) => {
@@ -397,31 +415,35 @@ impl Config {
             }
             set(&mut config.ninja, llvm.ninja);
             set(&mut config.llvm_enabled, llvm.enabled);
-            set(&mut config.llvm_assertions, llvm.assertions);
+            llvm_assertions = llvm.assertions;
             set(&mut config.llvm_optimize, llvm.optimize);
             set(&mut config.llvm_release_debuginfo, llvm.release_debuginfo);
             set(&mut config.llvm_version_check, llvm.version_check);
             set(&mut config.llvm_static_stdcpp, llvm.static_libstdcpp);
+            set(&mut config.llvm_link_shared, llvm.link_shared);
             config.llvm_targets = llvm.targets.clone();
             config.llvm_experimental_targets = llvm.experimental_targets.clone();
             config.llvm_link_jobs = llvm.link_jobs;
         }
 
         if let Some(ref rust) = toml.rust {
-            set(&mut config.rust_debug_assertions, rust.debug_assertions);
-            set(&mut config.rust_debuginfo, rust.debuginfo);
-            set(&mut config.rust_debuginfo_lines, rust.debuginfo_lines);
-            set(&mut config.rust_debuginfo_only_std, rust.debuginfo_only_std);
-            set(&mut config.rust_optimize, rust.optimize);
+            debug = rust.debug;
+            debug_assertions = rust.debug_assertions;
+            debuginfo = rust.debuginfo;
+            debuginfo_lines = rust.debuginfo_lines;
+            debuginfo_only_std = rust.debuginfo_only_std;
+            optimize = rust.optimize;
+            ignore_git = rust.ignore_git;
+            debug_jemalloc = rust.debug_jemalloc;
             set(&mut config.rust_optimize_tests, rust.optimize_tests);
             set(&mut config.rust_debuginfo_tests, rust.debuginfo_tests);
             set(&mut config.codegen_tests, rust.codegen_tests);
             set(&mut config.rust_rpath, rust.rpath);
-            set(&mut config.debug_jemalloc, rust.debug_jemalloc);
             set(&mut config.use_jemalloc, rust.use_jemalloc);
             set(&mut config.backtrace, rust.backtrace);
             set(&mut config.channel, rust.channel.clone());
-            set(&mut config.ignore_git, rust.ignore_git);
+            set(&mut config.rust_dist_src, rust.dist_src);
+            set(&mut config.quiet_tests, rust.quiet_tests);
             config.rustc_default_linker = rust.default_linker.clone();
             config.rustc_default_ar = rust.default_ar.clone();
             config.musl_root = rust.musl_root.clone().map(PathBuf::from);
@@ -476,224 +498,29 @@ impl Config {
             None => stage0_root.join(exe("cargo", &config.build)),
         };
 
-        // compat with `./configure` while we're still using that
-        if fs::metadata("config.mk").is_ok() {
-            config.update_with_config_mk();
-        }
+        // Now that we've reached the end of our configuration, infer the
+        // default values for all options that we haven't otherwise stored yet.
 
-        config
-    }
+        let default = config.channel == "nightly";
+        config.llvm_assertions = llvm_assertions.unwrap_or(default);
 
-    /// "Temporary" routine to parse `config.mk` into this configuration.
-    ///
-    /// While we still have `./configure` this implements the ability to decode
-    /// that configuration into this. This isn't exactly a full-blown makefile
-    /// parser, but hey it gets the job done!
-    fn update_with_config_mk(&mut self) {
-        let mut config = String::new();
-        File::open("config.mk").unwrap().read_to_string(&mut config).unwrap();
-        for line in config.lines() {
-            let mut parts = line.splitn(2, ":=").map(|s| s.trim());
-            let key = parts.next().unwrap();
-            let value = match parts.next() {
-                Some(n) if n.starts_with('\"') => &n[1..n.len() - 1],
-                Some(n) => n,
-                None => continue
-            };
-
-            macro_rules! check {
-                ($(($name:expr, $val:expr),)*) => {
-                    if value == "1" {
-                        $(
-                            if key == concat!("CFG_ENABLE_", $name) {
-                                $val = true;
-                                continue
-                            }
-                            if key == concat!("CFG_DISABLE_", $name) {
-                                $val = false;
-                                continue
-                            }
-                        )*
-                    }
-                }
-            }
+        let default = match &config.channel[..] {
+            "stable" | "beta" | "nightly" => true,
+            _ => false,
+        };
+        config.rust_debuginfo_lines = debuginfo_lines.unwrap_or(default);
+        config.rust_debuginfo_only_std = debuginfo_only_std.unwrap_or(default);
 
-            check! {
-                ("MANAGE_SUBMODULES", self.submodules),
-                ("COMPILER_DOCS", self.compiler_docs),
-                ("DOCS", self.docs),
-                ("LLVM_ASSERTIONS", self.llvm_assertions),
-                ("LLVM_RELEASE_DEBUGINFO", self.llvm_release_debuginfo),
-                ("OPTIMIZE_LLVM", self.llvm_optimize),
-                ("LLVM_VERSION_CHECK", self.llvm_version_check),
-                ("LLVM_STATIC_STDCPP", self.llvm_static_stdcpp),
-                ("LLVM_LINK_SHARED", self.llvm_link_shared),
-                ("OPTIMIZE", self.rust_optimize),
-                ("DEBUG_ASSERTIONS", self.rust_debug_assertions),
-                ("DEBUGINFO", self.rust_debuginfo),
-                ("DEBUGINFO_LINES", self.rust_debuginfo_lines),
-                ("DEBUGINFO_ONLY_STD", self.rust_debuginfo_only_std),
-                ("JEMALLOC", self.use_jemalloc),
-                ("DEBUG_JEMALLOC", self.debug_jemalloc),
-                ("RPATH", self.rust_rpath),
-                ("OPTIMIZE_TESTS", self.rust_optimize_tests),
-                ("DEBUGINFO_TESTS", self.rust_debuginfo_tests),
-                ("QUIET_TESTS", self.quiet_tests),
-                ("LOCAL_REBUILD", self.local_rebuild),
-                ("NINJA", self.ninja),
-                ("CODEGEN_TESTS", self.codegen_tests),
-                ("LOCKED_DEPS", self.locked_deps),
-                ("VENDOR", self.vendor),
-                ("FULL_BOOTSTRAP", self.full_bootstrap),
-                ("EXTENDED", self.extended),
-                ("SANITIZERS", self.sanitizers),
-                ("PROFILER", self.profiler),
-                ("DIST_SRC", self.rust_dist_src),
-                ("CARGO_OPENSSL_STATIC", self.openssl_static),
-            }
+        let default = debug == Some(true);
+        config.debug_jemalloc = debug_jemalloc.unwrap_or(default);
+        config.rust_debuginfo = debuginfo.unwrap_or(default);
+        config.rust_debug_assertions = debug_assertions.unwrap_or(default);
+        config.rust_optimize = optimize.unwrap_or(!default);
 
-            match key {
-                "CFG_BUILD" if value.len() > 0 => self.build = INTERNER.intern_str(value),
-                "CFG_HOST" if value.len() > 0 => {
-                    self.hosts.extend(value.split(" ").map(|s| INTERNER.intern_str(s)));
+        let default = config.channel == "dev";
+        config.ignore_git = ignore_git.unwrap_or(default);
 
-                }
-                "CFG_TARGET" if value.len() > 0 => {
-                    self.targets.extend(value.split(" ").map(|s| INTERNER.intern_str(s)));
-                }
-                "CFG_EXPERIMENTAL_TARGETS" if value.len() > 0 => {
-                    self.llvm_experimental_targets = Some(value.to_string());
-                }
-                "CFG_MUSL_ROOT" if value.len() > 0 => {
-                    self.musl_root = Some(parse_configure_path(value));
-                }
-                "CFG_MUSL_ROOT_X86_64" if value.len() > 0 => {
-                    let target = INTERNER.intern_str("x86_64-unknown-linux-musl");
-                    let target = self.target_config.entry(target).or_insert(Target::default());
-                    target.musl_root = Some(parse_configure_path(value));
-                }
-                "CFG_MUSL_ROOT_I686" if value.len() > 0 => {
-                    let target = INTERNER.intern_str("i686-unknown-linux-musl");
-                    let target = self.target_config.entry(target).or_insert(Target::default());
-                    target.musl_root = Some(parse_configure_path(value));
-                }
-                "CFG_MUSL_ROOT_ARM" if value.len() > 0 => {
-                    let target = INTERNER.intern_str("arm-unknown-linux-musleabi");
-                    let target = self.target_config.entry(target).or_insert(Target::default());
-                    target.musl_root = Some(parse_configure_path(value));
-                }
-                "CFG_MUSL_ROOT_ARMHF" if value.len() > 0 => {
-                    let target = INTERNER.intern_str("arm-unknown-linux-musleabihf");
-                    let target = self.target_config.entry(target).or_insert(Target::default());
-                    target.musl_root = Some(parse_configure_path(value));
-                }
-                "CFG_MUSL_ROOT_ARMV7" if value.len() > 0 => {
-                    let target = INTERNER.intern_str("armv7-unknown-linux-musleabihf");
-                    let target = self.target_config.entry(target).or_insert(Target::default());
-                    target.musl_root = Some(parse_configure_path(value));
-                }
-                "CFG_DEFAULT_AR" if value.len() > 0 => {
-                    self.rustc_default_ar = Some(value.to_string());
-                }
-                "CFG_DEFAULT_LINKER" if value.len() > 0 => {
-                    self.rustc_default_linker = Some(value.to_string());
-                }
-                "CFG_GDB" if value.len() > 0 => {
-                    self.gdb = Some(parse_configure_path(value));
-                }
-                "CFG_RELEASE_CHANNEL" => {
-                    self.channel = value.to_string();
-                }
-                "CFG_PREFIX" => {
-                    self.prefix = Some(PathBuf::from(value));
-                }
-                "CFG_SYSCONFDIR" => {
-                    self.sysconfdir = Some(PathBuf::from(value));
-                }
-                "CFG_DOCDIR" => {
-                    self.docdir = Some(PathBuf::from(value));
-                }
-                "CFG_BINDIR" => {
-                    self.bindir = Some(PathBuf::from(value));
-                }
-                "CFG_LIBDIR" => {
-                    self.libdir = Some(PathBuf::from(value));
-                }
-                "CFG_LIBDIR_RELATIVE" => {
-                    self.libdir_relative = Some(PathBuf::from(value));
-                }
-                "CFG_MANDIR" => {
-                    self.mandir = Some(PathBuf::from(value));
-                }
-                "CFG_LLVM_ROOT" if value.len() > 0 => {
-                    let target = self.target_config.entry(self.build.clone())
-                                     .or_insert(Target::default());
-                    let root = parse_configure_path(value);
-                    target.llvm_config = Some(push_exe_path(root, &["bin", "llvm-config"]));
-                }
-                "CFG_JEMALLOC_ROOT" if value.len() > 0 => {
-                    let target = self.target_config.entry(self.build.clone())
-                                     .or_insert(Target::default());
-                    target.jemalloc = Some(parse_configure_path(value).join("libjemalloc_pic.a"));
-                }
-                "CFG_ARM_LINUX_ANDROIDEABI_NDK" if value.len() > 0 => {
-                    let target = INTERNER.intern_str("arm-linux-androideabi");
-                    let target = self.target_config.entry(target).or_insert(Target::default());
-                    target.ndk = Some(parse_configure_path(value));
-                }
-                "CFG_ARMV7_LINUX_ANDROIDEABI_NDK" if value.len() > 0 => {
-                    let target = INTERNER.intern_str("armv7-linux-androideabi");
-                    let target = self.target_config.entry(target).or_insert(Target::default());
-                    target.ndk = Some(parse_configure_path(value));
-                }
-                "CFG_I686_LINUX_ANDROID_NDK" if value.len() > 0 => {
-                    let target = INTERNER.intern_str("i686-linux-android");
-                    let target = self.target_config.entry(target).or_insert(Target::default());
-                    target.ndk = Some(parse_configure_path(value));
-                }
-                "CFG_AARCH64_LINUX_ANDROID_NDK" if value.len() > 0 => {
-                    let target = INTERNER.intern_str("aarch64-linux-android");
-                    let target = self.target_config.entry(target).or_insert(Target::default());
-                    target.ndk = Some(parse_configure_path(value));
-                }
-                "CFG_X86_64_LINUX_ANDROID_NDK" if value.len() > 0 => {
-                    let target = INTERNER.intern_str("x86_64-linux-android");
-                    let target = self.target_config.entry(target).or_insert(Target::default());
-                    target.ndk = Some(parse_configure_path(value));
-                }
-                "CFG_LOCAL_RUST_ROOT" if value.len() > 0 => {
-                    let path = parse_configure_path(value);
-                    self.initial_rustc = push_exe_path(path.clone(), &["bin", "rustc"]);
-                    self.initial_cargo = push_exe_path(path, &["bin", "cargo"]);
-                }
-                "CFG_PYTHON" if value.len() > 0 => {
-                    let path = parse_configure_path(value);
-                    self.python = Some(path);
-                }
-                "CFG_ENABLE_CCACHE" if value == "1" => {
-                    self.ccache = Some(exe("ccache", &self.build));
-                }
-                "CFG_ENABLE_SCCACHE" if value == "1" => {
-                    self.ccache = Some(exe("sccache", &self.build));
-                }
-                "CFG_CONFIGURE_ARGS" if value.len() > 0 => {
-                    self.configure_args = value.split_whitespace()
-                                               .map(|s| s.to_string())
-                                               .collect();
-                }
-                "CFG_QEMU_ARMHF_ROOTFS" if value.len() > 0 => {
-                    let target = INTERNER.intern_str("arm-unknown-linux-gnueabihf");
-                    let target = self.target_config.entry(target).or_insert(Target::default());
-                    target.qemu_rootfs = Some(parse_configure_path(value));
-                }
-                "CFG_QEMU_AARCH64_ROOTFS" if value.len() > 0 => {
-                    let target = INTERNER.intern_str("aarch64-unknown-linux-gnu");
-                    let target = self.target_config.entry(target).or_insert(Target::default());
-                    target.qemu_rootfs = Some(parse_configure_path(value));
-                }
-                _ => {}
-            }
-        }
+        config
     }
 
     pub fn verbose(&self) -> bool {
@@ -705,30 +532,6 @@ impl Config {
     }
 }
 
-#[cfg(not(windows))]
-fn parse_configure_path(path: &str) -> PathBuf {
-    path.into()
-}
-
-#[cfg(windows)]
-fn parse_configure_path(path: &str) -> PathBuf {
-    // on windows, configure produces unix style paths e.g. /c/some/path but we
-    // only want real windows paths
-
-    use std::process::Command;
-    use build_helper;
-
-    // '/' is invalid in windows paths, so we can detect unix paths by the presence of it
-    if !path.contains('/') {
-        return path.into();
-    }
-
-    let win_path = build_helper::output(Command::new("cygpath").arg("-w").arg(path));
-    let win_path = win_path.trim();
-
-    win_path.into()
-}
-
 fn set<T>(field: &mut T, val: Option<T>) {
     if let Some(v) = val {
         *field = v;
diff --git a/src/bootstrap/configure.py b/src/bootstrap/configure.py
new file mode 100755
index 0000000000000..fa8b761336068
--- /dev/null
+++ b/src/bootstrap/configure.py
@@ -0,0 +1,414 @@
+#!/usr/bin/env python
+# Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+# file at the top-level directory of this distribution and at
+# http://rust-lang.org/COPYRIGHT.
+#
+# Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+# http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+# <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+# option. This file may not be copied, modified, or distributed
+# except according to those terms.
+
+# ignore-tidy-linelength
+
+import sys
+import os
+rust_dir = os.path.dirname(os.path.abspath(__file__))
+rust_dir = os.path.dirname(rust_dir)
+rust_dir = os.path.dirname(rust_dir)
+sys.path.append(os.path.join(rust_dir, "src", "bootstrap"))
+import bootstrap
+
+class Option:
+    def __init__(self, name, rustbuild, desc, value):
+        self.name = name
+        self.rustbuild = rustbuild
+        self.desc = desc
+        self.value = value
+
+options = []
+
+def o(*args):
+    options.append(Option(*args, value=False))
+
+def v(*args):
+    options.append(Option(*args, value=True))
+
+o("debug", "rust.debug", "debug mode; disables optimization unless `--enable-optimize` given")
+o("docs", "build.docs", "build standard library documentation")
+o("compiler-docs", "build.compiler-docs", "build compiler documentation")
+o("optimize-tests", "rust.optimize-tests", "build tests with optimizations")
+o("debuginfo-tests", "rust.debuginfo-tests", "build tests with debugger metadata")
+o("quiet-tests", "rust.quiet-tests", "enable quieter output when running tests")
+o("ccache", "llvm.ccache", "invoke gcc/clang via ccache to reuse object files between builds")
+o("sccache", None, "invoke gcc/clang via sccache to reuse object files between builds")
+o("local-rust", None, "use an installed rustc rather than downloading a snapshot")
+v("local-rust-root", None, "set prefix for local rust binary")
+o("local-rebuild", "build.local-rebuild", "assume local-rust matches the current version, for rebuilds; implies local-rust, and is implied if local-rust already matches the current version")
+o("llvm-static-stdcpp", "llvm.static-libstdcpp", "statically link to libstdc++ for LLVM")
+o("llvm-link-shared", "llvm.link-shared", "prefer shared linking to LLVM (llvm-config --link-shared)")
+o("rpath", "rust.rpath", "build rpaths into rustc itself")
+o("llvm-version-check", "llvm.version-check", "check if the LLVM version is supported, build anyway")
+o("codegen-tests", "rust.codegen-tests", "run the src/test/codegen tests")
+o("option-checking", None, "complain about unrecognized options in this configure script")
+o("ninja", "llvm.ninja", "build LLVM using the Ninja generator (for MSVC, requires building in the correct environment)")
+o("locked-deps", "build.locked-deps", "force Cargo.lock to be up to date")
+o("vendor", "build.vendor", "enable usage of vendored Rust crates")
+o("sanitizers", "build.sanitizers", "build the sanitizer runtimes (asan, lsan, msan, tsan)")
+o("dist-src", "rust.dist-src", "when building tarballs enables building a source tarball")
+o("cargo-openssl-static", "build.openssl-static", "static openssl in cargo")
+o("profiler", "build.profiler", "build the profiler runtime")
+
+# Optimization and debugging options. These may be overridden by the release
+# channel, etc.
+o("optimize", "rust.optimize", "build optimized rust code")
+o("optimize-llvm", "llvm.optimize", "build optimized LLVM")
+o("llvm-assertions", "llvm.assertions", "build LLVM with assertions")
+o("debug-assertions", "rust.debug-assertions", "build with debugging assertions")
+o("llvm-release-debuginfo", "llvm.release-debuginfo", "build LLVM with debugger metadata")
+o("debuginfo", "rust.debuginfo", "build with debugger metadata")
+o("debuginfo-lines", "rust.debuginfo-lines", "build with line number debugger metadata")
+o("debuginfo-only-std", "rust.debuginfo-only-std", "build only libstd with debugging information")
+o("debug-jemalloc", "rust.debug-jemalloc", "build jemalloc with --enable-debug --enable-fill")
+
+v("prefix", "install.prefix", "set installation prefix")
+v("localstatedir", "install.localstatedir", "local state directory")
+v("datadir", "install.datadir", "install data")
+v("sysconfdir", "install.sysconfdir", "install system configuration files")
+v("infodir", "install.infodir", "install additional info")
+v("libdir", "install.libdir", "install libraries")
+v("mandir", "install.mandir", "install man pages in PATH")
+v("docdir", "install.docdir", "install documentation in PATH")
+v("bindir", "install.bindir", "install binaries")
+
+v("llvm-root", None, "set LLVM root")
+v("python", "build.python", "set path to python")
+v("jemalloc-root", None, "set directory where libjemalloc_pic.a is located")
+v("android-cross-path", "target.arm-linux-androideabi.android-ndk",
+  "Android NDK standalone path (deprecated)")
+v("i686-linux-android-ndk", "target.i686-linux-android.android-ndk",
+  "i686-linux-android NDK standalone path")
+v("arm-linux-androideabi-ndk", "target.arm-linux-androideabi.android-ndk",
+  "arm-linux-androideabi NDK standalone path")
+v("armv7-linux-androideabi-ndk", "target.armv7-linux-androideabi.android-ndk",
+  "armv7-linux-androideabi NDK standalone path")
+v("aarch64-linux-android-ndk", "target.aarch64-linux-android.android-ndk",
+  "aarch64-linux-android NDK standalone path")
+v("x86_64-linux-android-ndk", "target.x86_64-linux-android.android-ndk",
+  "x86_64-linux-android NDK standalone path")
+v("musl-root", "target.x86_64-unknown-linux-musl.musl-root",
+  "MUSL root installation directory (deprecated)")
+v("musl-root-x86_64", "target.x86_64-unknown-linux-musl.musl-root",
+  "x86_64-unknown-linux-musl install directory")
+v("musl-root-i686", "target.i686-unknown-linux-musl.musl-root",
+  "i686-unknown-linux-musl install directory")
+v("musl-root-arm", "target.arm-unknown-linux-musleabi.musl-root",
+  "arm-unknown-linux-musleabi install directory")
+v("musl-root-armhf", "target.arm-unknown-linux-musleabihf.musl-root",
+  "arm-unknown-linux-musleabihf install directory")
+v("musl-root-armv7", "target.armv7-unknown-linux-musleabihf.musl-root",
+  "armv7-unknown-linux-musleabihf install directory")
+v("qemu-armhf-rootfs", "target.arm-unknown-linux-gnueabihf.qemu-rootfs",
+  "rootfs in qemu testing, you probably don't want to use this")
+v("qemu-aarch64-rootfs", "target.aarch64-unknown-linux-gnu.qemu-rootfs",
+  "rootfs in qemu testing, you probably don't want to use this")
+v("experimental-targets", "llvm.experimental-targets",
+  "experimental LLVM targets to build")
+v("release-channel", "rust.channel", "the name of the release channel to build")
+
+# Used on systems where "cc" and "ar" are unavailable
+v("default-linker", "rust.default-linker", "the default linker")
+v("default-ar", "rust.default-ar", "the default ar")
+
+# Many of these are saved below during the "writing configuration" step
+# (others are conditionally saved).
+o("manage-submodules", "build.submodules", "let the build manage the git submodules")
+o("jemalloc", "rust.use-jemalloc", "build liballoc with jemalloc")
+o("full-bootstrap", "build.full-bootstrap", "build three compilers instead of two")
+o("extended", "build.extended", "build an extended rust tool set")
+
+v("build", "build.build", "GNUs ./configure syntax LLVM build triple")
+v("host", None, "GNUs ./configure syntax LLVM host triples")
+v("target", None, "GNUs ./configure syntax LLVM target triples")
+
+v("set", None, "set arbitrary key/value pairs in TOML configuration")
+
+def p(msg):
+    print("configure: " + msg)
+
+def err(msg):
+    print("configure: error: " + msg)
+    sys.exit(1)
+
+if '--help' in sys.argv or '-h' in sys.argv:
+    print('Usage: ./configure [options]')
+    print('')
+    print('Options')
+    for option in options:
+        if 'android' in option.name:
+            # no one needs to know about these obscure options
+            continue
+        if option.value:
+            print('\t{:30} {}'.format('--{}=VAL'.format(option.name), option.desc))
+        else:
+            print('\t{:30} {}'.format('--enable-{}'.format(option.name), option.desc))
+    print('')
+    print('This configure script is a thin configuration shim over the true')
+    print('configuration system, `config.toml`. You can explore the comments')
+    print('in `config.toml.example` next to this configure script to see')
+    print('more information about what each option is. Additionally you can')
+    print('pass `--set` as an argument to set arbitrary key/value pairs')
+    print('in the TOML configuration if desired')
+    print('')
+    print('Also note that all options which take `--enable` can similarly')
+    print('be passed with `--disable-foo` to forcibly disable the option')
+    sys.exit(0)
+
+# Parse all command line arguments into one of these three lists, handling
+# boolean and value-based options separately
+unknown_args = []
+need_value_args = []
+known_args = {}
+
+p("processing command line")
+i = 1
+while i < len(sys.argv):
+    arg = sys.argv[i]
+    i += 1
+    if not arg.startswith('--'):
+        unknown_args.append(arg)
+        continue
+
+    found = False
+    for option in options:
+        value = None
+        if option.value:
+            keyval = arg[2:].split('=', 1)
+            key = keyval[0]
+            if option.name != key:
+                continue
+
+            if len(keyval) > 1:
+                value = keyval[1]
+            elif i < len(sys.argv):
+                value = sys.argv[i]
+                i += 1
+            else:
+                need_value_args.append(arg)
+                continue
+        else:
+            if arg[2:] == 'enable-' + option.name:
+                value = True
+            elif arg[2:] == 'disable-' + option.name:
+                value = False
+            else:
+                continue
+
+        found = True
+        if not option.name in known_args:
+            known_args[option.name] = []
+        known_args[option.name].append((option, value))
+        break
+
+    if not found:
+        unknown_args.append(arg)
+p("")
+
+if 'option-checking' not in known_args or known_args['option-checking'][1]:
+    if len(unknown_args) > 0:
+        err("Option '" + unknown_args[0] + "' is not recognized")
+    if len(need_value_args) > 0:
+        err("Option '{0}' needs a value ({0}=val)".format(need_value_args[0]))
+
+# Parse all known arguments into a configuration structure that reflects the
+# TOML we're going to write out
+config = {}
+
+def build():
+    if 'build' in known_args:
+        return known_args['build'][0][1]
+    return bootstrap.default_build_triple()
+
+def set(key, value):
+      s = "{:20} := {}".format(key, value)
+      if len(s) < 70:
+          p(s)
+      else:
+          p(s[:70] + " ...")
+
+      arr = config
+      parts = key.split('.')
+      for i, part in enumerate(parts):
+          if i == len(parts) - 1:
+              arr[part] = value
+          else:
+              if not part in arr:
+                  arr[part] = {}
+              arr = arr[part]
+
+for key in known_args:
+    # The `set` option is special and can be passed a bunch of times
+    if key == 'set':
+        for option, value in known_args[key]:
+            keyval = value.split('=', 1)
+            if len(keyval) == 1 or keyval[1] == "true":
+                value = True
+            elif keyval[1] == "false":
+                value = False
+            else:
+                value = keyval[1]
+            set(keyval[0], value)
+        continue
+
+    # Ensure each option is only passed once
+    arr = known_args[key]
+    if len(arr) > 1:
+        err("Option '{}' provided more than once".format(key))
+    option, value = arr[0]
+
+    # If we have a clear avenue to set our value in rustbuild, do so
+    if option.rustbuild is not None:
+        set(option.rustbuild, value)
+        continue
+
+    # Otherwise we're a "special" option and need some extra handling, so do
+    # that here.
+    if option.name == 'sccache':
+        set('llvm.ccache', 'sccache')
+    elif option.name == 'local-rust':
+        for path in os.environ['PATH'].split(os.pathsep):
+            if os.path.exists(path + '/rustc'):
+                set('build.rustc', path + '/rustc')
+                break
+        for path in os.environ['PATH'].split(os.pathsep):
+            if os.path.exists(path + '/cargo'):
+                set('build.cargo', path + '/cargo')
+                break
+    elif option.name == 'local-rust-root':
+        set('build.rustc', value + '/bin/rustc')
+        set('build.cargo', value + '/bin/cargo')
+    elif option.name == 'llvm-root':
+        set('target.{}.llvm-config'.format(build()), value + '/bin/llvm-config')
+    elif option.name == 'jemalloc-root':
+        set('target.{}.jemalloc'.format(build()), value + '/libjemalloc_pic.a')
+    elif option.name == 'host':
+        set('build.host', value.split(','))
+    elif option.name == 'target':
+        set('build.target', value.split(','))
+    elif option.name == 'option-checking':
+        # this was handled above
+        pass
+    else:
+        raise RuntimeError("unhandled option {}".format(option.name))
+
+set('build.configure-args', sys.argv[1:])
+
+# "Parse" the `config.toml.example` file into the various sections, and we'll
+# use this as a template of a `config.toml` to write out which preserves
+# all the various comments and whatnot.
+#
+# Note that the `target` section is handled separately as we'll duplicate it
+# per configure dtarget, so there's a bit of special handling for that here.
+sections = {}
+cur_section = None
+sections[None] = []
+section_order = [None]
+targets = {}
+
+for line in open(rust_dir + '/config.toml.example').read().split("\n"):
+    if line.startswith('['):
+        cur_section = line[1:-1]
+        if cur_section.startswith('target'):
+            cur_section = 'target'
+        elif '.' in cur_section:
+            raise RuntimeError("don't know how to deal with section: {}".format(cur_section))
+        sections[cur_section] = [line]
+        section_order.append(cur_section)
+    else:
+        sections[cur_section].append(line)
+
+# Fill out the `targets` array by giving all configured targets a copy of the
+# `target` section we just loaded from the example config
+configured_targets = [build()]
+if 'build' in config:
+    if 'host' in config['build']:
+        configured_targets += config['build']['host']
+    if 'target' in config['build']:
+        configured_targets += config['build']['target']
+if 'target' in config:
+    for target in config['target']:
+        configured_targets.append(target)
+for target in configured_targets:
+    targets[target] = sections['target'][:]
+    targets[target][0] = targets[target][0].replace("x86_64-unknown-linux-gnu", target)
+
+# Here we walk through the constructed configuration we have from the parsed
+# command line arguemnts. We then apply each piece of configuration by
+# basically just doing a `sed` to change the various configuration line to what
+# we've got configure.
+def to_toml(value):
+    if isinstance(value, bool):
+        if value:
+            return "true"
+        else:
+            return "false"
+    elif isinstance(value, list):
+        return '[' + ', '.join(map(to_toml, value)) + ']'
+    elif isinstance(value, str):
+        return "'" + value + "'"
+    else:
+        raise 'no toml'
+
+def configure_section(lines, config):
+    for key in config:
+        value = config[key]
+        found = False
+        for i, line in enumerate(lines):
+            if not line.startswith('#' + key + ' = '):
+                continue
+            found = True
+            lines[i] = "{} = {}".format(key, to_toml(value))
+            break
+        if not found:
+            raise RuntimeError("failed to find config line for {}".format(key))
+
+for section_key in config:
+    section_config = config[section_key]
+    if not section_key in sections:
+        raise RuntimeError("config key {} not in sections".format(key))
+
+    if section_key == 'target':
+        for target in section_config:
+            configure_section(targets[target], section_config[target])
+    else:
+        configure_section(sections[section_key], section_config)
+
+# Now that we've built up our `config.toml`, write it all out in the same
+# order that we read it in.
+p("")
+p("writing `config.toml` in current directory")
+with open('config.toml', 'w') as f:
+    for section in section_order:
+        if section == 'target':
+            for target in targets:
+                for line in targets[target]:
+                    f.write(line + "\n")
+        else:
+            for line in sections[section]:
+                f.write(line + "\n")
+
+with open('Makefile', 'w') as f:
+    contents = os.path.join(rust_dir, 'src', 'bootstrap', 'mk', 'Makefile.in')
+    contents = open(contents).read()
+    contents = contents.replace("$(CFG_SRC_DIR)", rust_dir + '/')
+    contents = contents.replace("$(CFG_PYTHON)", sys.executable)
+    f.write(contents)
+
+# Finally, clean up with a bit of a help message
+relpath = os.path.dirname(__file__)
+if relpath == '':
+    relpath = '.'
+
+p("")
+p("run `python {}/x.py --help`".format(relpath))
+p("")
diff --git a/src/bootstrap/dist.rs b/src/bootstrap/dist.rs
index bfcfb5f9a37f8..2e243b022c314 100644
--- a/src/bootstrap/dist.rs
+++ b/src/bootstrap/dist.rs
@@ -724,6 +724,9 @@ impl Step for Src {
         let dst_src = dst.join("rust");
         t!(fs::create_dir_all(&dst_src));
 
+        let src_files = [
+            "src/Cargo.lock",
+        ];
         // This is the reduced set of paths which will become the rust-src component
         // (essentially libstd and all of its path dependencies)
         let std_src_dirs = [
@@ -754,11 +757,14 @@ impl Step for Src {
             "src/libprofiler_builtins",
         ];
         let std_src_dirs_exclude = [
-            "src/compiler-rt/test",
+            "src/libcompiler_builtins/compiler-rt/test",
             "src/jemalloc/test/unit",
         ];
 
         copy_src_dirs(build, &std_src_dirs[..], &std_src_dirs_exclude[..], &dst_src);
+        for file in src_files.iter() {
+            copy(&build.src.join(file), &dst_src.join(file));
+        }
 
         // Create source tarball in rust-installer format
         let mut cmd = rust_installer(builder);
@@ -822,6 +828,7 @@ impl Step for PlainSourceTarball {
             "RELEASES.md",
             "configure",
             "x.py",
+            "config.toml.example",
         ];
         let src_dirs = [
             "man",
@@ -1081,8 +1088,14 @@ impl Step for Rls {
            .arg("--output-dir").arg(&distdir(build))
            .arg("--non-installed-overlay").arg(&overlay)
            .arg(format!("--package-name={}-{}", name, target))
-           .arg("--component-name=rls")
            .arg("--legacy-manifest-dirs=rustlib,cargo");
+
+        if build.config.channel == "nightly" {
+            cmd.arg("--component-name=rls");
+        } else {
+            cmd.arg("--component-name=rls-preview");
+        }
+
         build.run(&mut cmd);
         distdir(build).join(format!("{}-{}.tar.gz", name, target))
     }
diff --git a/src/bootstrap/doc.rs b/src/bootstrap/doc.rs
index 86f5346bea1fb..b9a52a66793df 100644
--- a/src/bootstrap/doc.rs
+++ b/src/bootstrap/doc.rs
@@ -669,11 +669,6 @@ impl Step for ErrorIndex {
         let build = builder.build;
         let target = self.target;
 
-        builder.ensure(compile::Rustc {
-            compiler: builder.compiler(0, build.build),
-            target,
-        });
-
         println!("Documenting error index ({})", target);
         let out = build.doc_out(target);
         t!(fs::create_dir_all(&out));
diff --git a/src/bootstrap/flags.rs b/src/bootstrap/flags.rs
index a84d43d3deede..7546d7fd4f07a 100644
--- a/src/bootstrap/flags.rs
+++ b/src/bootstrap/flags.rs
@@ -136,7 +136,7 @@ To learn more about a subcommand, run `./x.py <subcommand> -h`");
             None => {
                 // No subcommand -- show the general usage and subcommand help
                 println!("{}\n", subcommand_help);
-                process::exit(0);
+                process::exit(1);
             }
         };
 
diff --git a/src/bootstrap/lib.rs b/src/bootstrap/lib.rs
index 55358f2ffcb73..f21b382619d0a 100644
--- a/src/bootstrap/lib.rs
+++ b/src/bootstrap/lib.rs
@@ -123,7 +123,6 @@ extern crate build_helper;
 extern crate serde_derive;
 #[macro_use]
 extern crate lazy_static;
-extern crate serde;
 extern crate serde_json;
 extern crate cmake;
 extern crate filetime;
@@ -718,7 +717,7 @@ impl Build {
     fn force_use_stage1(&self, compiler: Compiler, target: Interned<String>) -> bool {
         !self.config.full_bootstrap &&
             compiler.stage >= 2 &&
-            self.hosts.iter().any(|h| *h == target)
+            (self.hosts.iter().any(|h| *h == target) || target == self.build)
     }
 
     /// Returns the directory that OpenSSL artifacts are compiled into if
diff --git a/src/bootstrap/mk/Makefile.in b/src/bootstrap/mk/Makefile.in
index 9410927824cc1..67495b891f80d 100644
--- a/src/bootstrap/mk/Makefile.in
+++ b/src/bootstrap/mk/Makefile.in
@@ -8,8 +8,6 @@
 # option. This file may not be copied, modified, or distributed
 # except according to those terms.
 
-include config.mk
-
 ifdef VERBOSE
 Q :=
 BOOTSTRAP_ARGS := -v
diff --git a/src/bootstrap/native.rs b/src/bootstrap/native.rs
index 0a307e72bf61d..8173903c03440 100644
--- a/src/bootstrap/native.rs
+++ b/src/bootstrap/native.rs
@@ -407,6 +407,7 @@ impl Step for Openssl {
             "i686-unknown-freebsd" => "BSD-x86-elf",
             "i686-unknown-linux-gnu" => "linux-elf",
             "i686-unknown-linux-musl" => "linux-elf",
+            "i686-unknown-netbsd" => "BSD-x86-elf",
             "mips-unknown-linux-gnu" => "linux-mips32",
             "mips64-unknown-linux-gnuabi64" => "linux64-mips64",
             "mips64el-unknown-linux-gnuabi64" => "linux64-mips64",
diff --git a/src/bootstrap/tool.rs b/src/bootstrap/tool.rs
index d798e8de3dffa..b129aa113a030 100644
--- a/src/bootstrap/tool.rs
+++ b/src/bootstrap/tool.rs
@@ -120,6 +120,7 @@ fn prepare_tool_cargo(
     }
 
     cargo.env("CFG_RELEASE_CHANNEL", &build.config.channel);
+    cargo.env("CFG_VERSION", build.rust_version());
 
     let info = GitInfo::new(&build.config, &dir);
     if let Some(sha) = info.sha() {
@@ -198,7 +199,7 @@ tool!(
     Linkchecker, "src/tools/linkchecker", "linkchecker", Mode::Libstd;
     CargoTest, "src/tools/cargotest", "cargotest", Mode::Libstd;
     Compiletest, "src/tools/compiletest", "compiletest", Mode::Libtest;
-    BuildManifest, "src/tools/build-manifest", "build-manifest", Mode::Librustc;
+    BuildManifest, "src/tools/build-manifest", "build-manifest", Mode::Libstd;
     RemoteTestClient, "src/tools/remote-test-client", "remote-test-client", Mode::Libstd;
     RustInstaller, "src/tools/rust-installer", "rust-installer", Mode::Libstd;
 );
@@ -340,6 +341,44 @@ impl Step for Cargo {
     }
 }
 
+#[derive(Debug, Copy, Clone, Hash, PartialEq, Eq)]
+pub struct Clippy {
+    pub compiler: Compiler,
+    pub target: Interned<String>,
+}
+
+impl Step for Clippy {
+    type Output = PathBuf;
+    const DEFAULT: bool = false;
+    const ONLY_HOSTS: bool = true;
+
+    fn should_run(run: ShouldRun) -> ShouldRun {
+        run.path("src/tools/clippy")
+    }
+
+    fn make_run(run: RunConfig) {
+        run.builder.ensure(Clippy {
+            compiler: run.builder.compiler(run.builder.top_stage, run.builder.build.build),
+            target: run.target,
+        });
+    }
+
+    fn run(self, builder: &Builder) -> PathBuf {
+        // Clippy depends on procedural macros (serde), which requires a full host
+        // compiler to be available, so we need to depend on that.
+        builder.ensure(compile::Rustc {
+            compiler: self.compiler,
+            target: builder.build.build,
+        });
+        builder.ensure(ToolBuild {
+            compiler: self.compiler,
+            target: self.target,
+            tool: "clippy",
+            mode: Mode::Librustc,
+        })
+    }
+}
+
 #[derive(Debug, Copy, Clone, Hash, PartialEq, Eq)]
 pub struct Rls {
     pub compiler: Compiler,
diff --git a/src/bootstrap/util.rs b/src/bootstrap/util.rs
index 092fb04637ba7..234d937823fb5 100644
--- a/src/bootstrap/util.rs
+++ b/src/bootstrap/util.rs
@@ -279,7 +279,7 @@ pub fn symlink_dir(src: &Path, dest: &Path) -> io::Result<()> {
                                 ptr::null_mut());
 
             let mut data = [0u8; MAXIMUM_REPARSE_DATA_BUFFER_SIZE];
-            let mut db = data.as_mut_ptr()
+            let db = data.as_mut_ptr()
                             as *mut REPARSE_MOUNTPOINT_DATA_BUFFER;
             let buf = &mut (*db).ReparseTarget as *mut _;
             let mut i = 0;
diff --git a/src/ci/docker/x86_64-gnu-distcheck/Dockerfile b/src/ci/docker/x86_64-gnu-distcheck/Dockerfile
index 786f59eb9f761..f16dd9809981e 100644
--- a/src/ci/docker/x86_64-gnu-distcheck/Dockerfile
+++ b/src/ci/docker/x86_64-gnu-distcheck/Dockerfile
@@ -18,6 +18,6 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
 COPY scripts/sccache.sh /scripts/
 RUN sh /scripts/sccache.sh
 
-ENV RUST_CONFIGURE_ARGS --build=x86_64-unknown-linux-gnu
+ENV RUST_CONFIGURE_ARGS --build=x86_64-unknown-linux-gnu --set rust.ignore-git=false
 ENV SCRIPT python2.7 ../x.py test distcheck
 ENV DIST_SRC 1
diff --git a/src/doc/unstable-book/src/language-features/generators.md b/src/doc/unstable-book/src/language-features/generators.md
new file mode 100644
index 0000000000000..7a559a7bec866
--- /dev/null
+++ b/src/doc/unstable-book/src/language-features/generators.md
@@ -0,0 +1,245 @@
+# `generators`
+
+The tracking issue for this feature is: [#43122]
+
+[#43122]: https://github.com/rust-lang/rust/issues/43122
+
+------------------------
+
+The `generators` feature gate in Rust allows you to define generator or
+coroutine literals. A generator is a "resumable function" that syntactically
+resembles a closure but compiles to much different semantics in the compiler
+itself. The primary feature of a generator is that it can be suspended during
+execution to be resumed at a later date. Generators use the `yield` keyword to
+"return", and then the caller can `resume` a generator to resume execution just
+after the `yield` keyword.
+
+Generators are an extra-unstable feature in the compiler right now. Added in
+[RFC 2033] they're mostly intended right now as a information/constraint
+gathering phase. The intent is that experimentation can happen on the nightly
+compiler before actual stabilization. A further RFC will be required to
+stabilize generators/coroutines and will likely contain at least a few small
+tweaks to the overall design.
+
+[RFC 2033]: https://github.com/rust-lang/rfcs/pull/2033
+
+A syntactical example of a generator is:
+
+```rust
+#![feature(generators, generator_trait)]
+
+use std::ops::{Generator, GeneratorState};
+
+fn main() {
+    let mut generator = || {
+        yield 1;
+        return "foo"
+    };
+
+    match generator.resume() {
+        GeneratorState::Yielded(1) => {}
+        _ => panic!("unexpected value from resume"),
+    }
+    match generator.resume() {
+        GeneratorState::Complete("foo") => {}
+        _ => panic!("unexpected value from resume"),
+    }
+}
+```
+
+Generators are closure-like literals which can contain a `yield` statement. The
+`yield` statement takes an optional expression of a value to yield out of the
+generator. All generator literals implement the `Generator` trait in the
+`std::ops` module. The `Generator` trait has one main method, `resume`, which
+resumes execution of the generator at the previous suspension point.
+
+An example of the control flow of generators is that the following example
+prints all numbers in order:
+
+```rust
+#![feature(generators, generator_trait)]
+
+use std::ops::Generator;
+
+fn main() {
+    let mut generator = || {
+        println!("2");
+        yield;
+        println!("4");
+    };
+
+    println!("1");
+    generator.resume();
+    println!("3");
+    generator.resume();
+    println!("5");
+}
+```
+
+At this time the main intended use case of generators is an implementation
+primitive for async/await syntax, but generators will likely be extended to
+ergonomic implementations of iterators and other primitives in the future.
+Feedback on the design and usage is always appreciated!
+
+### The `Generator` trait
+
+The `Generator` trait in `std::ops` currently looks like:
+
+```
+# #![feature(generator_trait)]
+# use std::ops::GeneratorState;
+
+pub trait Generator {
+    type Yield;
+    type Return;
+    fn resume(&mut self) -> GeneratorState<Self::Yield, Self::Return>;
+}
+```
+
+The `Generator::Yield` type is the type of values that can be yielded with the
+`yield` statement. The `Generator::Return` type is the returned type of the
+generator. This is typically the last expression in a generator's definition or
+any value passed to `return` in a generator. The `resume` function is the entry
+point for executing the `Generator` itself.
+
+The return value of `resume`, `GeneratorState`, looks like:
+
+```
+pub enum GeneratorState<Y, R> {
+    Yielded(Y),
+    Complete(R),
+}
+```
+
+The `Yielded` variant indicates that the generator can later be resumed. This
+corresponds to a `yield` point in a generator. The `Complete` variant indicates
+that the generator is complete and cannot be resumed again. Calling `resume`
+after a generator has returned `Complete` will likely result in a panic of the
+program.
+
+### Closure-like semantics
+
+The closure-like syntax for generators alludes to the fact that they also have
+closure-like semantics. Namely:
+
+* When created, a generator executes no code. A closure literal does not
+  actually execute any of the closure's code on construction, and similarly a
+  generator literal does not execute any code inside the generator when
+  constructed.
+
+* Generators can capture outer variables by reference or by move, and this can
+  be tweaked with the `move` keyword at the beginning of the closure. Like
+  closures all generators will have an implicit environment which is inferred by
+  the compiler. Outer variables can be moved into a generator for use as the
+  generator progresses.
+
+* Generator literals produce a value with a unique type which implements the
+  `std::ops::Generator` trait. This allows actual execution of the generator
+  through the `Generator::resume` method as well as also naming it in return
+  types and such.
+
+* Traits like `Send` and `Sync` are automatically implemented for a `Generator`
+  depending on the captured variables of the environment. Unlike closures though
+  generators also depend on variables live across suspension points. This means
+  that although the ambient environment may be `Send` or `Sync`, the generator
+  itself may not be due to internal variables live across `yield` points being
+  not-`Send` or not-`Sync`. Note, though, that generators, like closures, do
+  not implement traits like `Copy` or `Clone` automatically.
+
+* Whenever a generator is dropped it will drop all captured environment
+  variables.
+
+Note that unlike closures generators at this time cannot take any arguments.
+That is, generators must always look like `|| { ... }`. This restriction may be
+lifted at a future date, the design is ongoing!
+
+### Generators as state machines
+
+In the compiler generators are currently compiled as state machines. Each
+`yield` expression will correspond to a different state that stores all live
+variables over that suspension point. Resumption of a generator will dispatch on
+the current state and then execute internally until a `yield` is reached, at
+which point all state is saved off in the generator and a value is returned.
+
+Let's take a look at an example to see what's going on here:
+
+```rust
+#![feature(generators, generator_trait)]
+
+use std::ops::Generator;
+
+fn main() {
+    let ret = "foo";
+    let mut generator = move || {
+        yield 1;
+        return ret
+    };
+
+    generator.resume();
+    generator.resume();
+}
+```
+
+This generator literal will compile down to something similar to:
+
+```rust
+#![feature(generators, generator_trait)]
+
+use std::ops::{Generator, GeneratorState};
+
+fn main() {
+    let ret = "foo";
+    let mut generator = {
+        enum __Generator {
+            Start(&'static str),
+            Yield1(&'static str),
+            Done,
+        }
+
+        impl Generator for __Generator {
+            type Yield = i32;
+            type Return = &'static str;
+
+            fn resume(&mut self) -> GeneratorState<i32, &'static str> {
+                use std::mem;
+                match mem::replace(self, __Generator::Done) {
+                    __Generator::Start(s) => {
+                        *self = __Generator::Yield1(s);
+                        GeneratorState::Yielded(1)
+                    }
+
+                    __Generator::Yield1(s) => {
+                        *self = __Generator::Done;
+                        GeneratorState::Complete(s)
+                    }
+
+                    __Generator::Done => {
+                        panic!("generator resumed after completion")
+                    }
+                }
+            }
+        }
+
+        __Generator::Start(ret)
+    };
+
+    generator.resume();
+    generator.resume();
+}
+```
+
+Notably here we can see that the compiler is generating a fresh type,
+`__Generator` in this case. This type has a number of states (represented here
+as an `enum`) corresponding to each of the conceptual states of the generator.
+At the beginning we're closing over our outer variable `foo` and then that
+variable is also live over the `yield` point, so it's stored in both states.
+
+When the generator starts it'll immediately yield 1, but it saves off its state
+just before it does so indicating that it has reached the yield point. Upon
+resuming again we'll execute the `return ret` which returns the `Complete`
+state.
+
+Here we can also note that the `Done` state, if resumed, panics immediately as
+it's invalid to resume a completed generator. It's also worth noting that this
+is just a rough desugaring, not a normative specification for what the compiler
+does.
diff --git a/src/doc/unstable-book/src/language-features/match-beginning-vert.md b/src/doc/unstable-book/src/language-features/match-beginning-vert.md
new file mode 100644
index 0000000000000..f0a51af7fd1c8
--- /dev/null
+++ b/src/doc/unstable-book/src/language-features/match-beginning-vert.md
@@ -0,0 +1,23 @@
+# `match_beginning_vert`
+
+The tracking issue for this feature is [#44101].
+
+With this feature enabled, you are allowed to add a '|' to the beginning of a
+match arm:
+
+```rust
+#![feature(match_beginning_vert)]
+
+enum Foo { A, B, C }
+
+fn main() {
+    let x = Foo::A;
+    match x {
+        | Foo::A 
+        | Foo::B => println!("AB"),
+        | Foo::C => println!("C"),
+    }
+}
+```
+
+[#44101]: https://github.com/rust-lang/rust/issues/44101
\ No newline at end of file
diff --git a/src/doc/unstable-book/src/library-features/splice.md b/src/doc/unstable-book/src/library-features/splice.md
index ca7f78a8f79e5..dae4475257a02 100644
--- a/src/doc/unstable-book/src/library-features/splice.md
+++ b/src/doc/unstable-book/src/library-features/splice.md
@@ -18,7 +18,6 @@ let mut s = String::from("α is alpha, β is beta");
 let beta_offset = s.find('β').unwrap_or(s.len());
 
 // Replace the range up until the β from the string
-let t: String = s.splice(..beta_offset, "Α is capital alpha; ").collect();
-assert_eq!(t, "α is alpha, ");
+s.splice(..beta_offset, "Α is capital alpha; ");
 assert_eq!(s, "Α is capital alpha; β is beta");
 ```
\ No newline at end of file
diff --git a/src/liballoc/allocator.rs b/src/liballoc/allocator.rs
index f14f27023249e..5a9cd82b9d119 100644
--- a/src/liballoc/allocator.rs
+++ b/src/liballoc/allocator.rs
@@ -464,6 +464,29 @@ impl fmt::Display for CannotReallocInPlace {
 ///  * if a layout `k` fits a memory block (denoted by `ptr`)
 ///    currently allocated via an allocator `a`, then it is legal to
 ///    use that layout to deallocate it, i.e. `a.dealloc(ptr, k);`.
+///
+/// # Unsafety
+///
+/// The `Alloc` trait is an `unsafe` trait for a number of reasons, and
+/// implementors must ensure that they adhere to these contracts:
+///
+/// * Pointers returned from allocation functions must point to valid memory and
+///   retain their validity until at least the instance of `Alloc` is dropped
+///   itself.
+///
+/// * It's undefined behavior if global allocators unwind.  This restriction may
+///   be lifted in the future, but currently a panic from any of these
+///   functions may lead to memory unsafety. Note that as of the time of this
+///   writing allocators *not* intending to be global allocators can still panic
+///   in their implementation without violating memory safety.
+///
+/// * `Layout` queries and calculations in general must be correct. Callers of
+///   this trait are allowed to rely on the contracts defined on each method,
+///   and implementors must ensure such contracts remain true.
+///
+/// Note that this list may get tweaked over time as clarifications are made in
+/// the future. Additionally global allocators may gain unique requirements for
+/// how to safely implement one in the future as well.
 pub unsafe trait Alloc {
 
     // (Note: existing allocators have unspecified but well-defined
diff --git a/src/liballoc/boxed.rs b/src/liballoc/boxed.rs
index 82aac4dbf6334..d9f4a2217db4e 100644
--- a/src/liballoc/boxed.rs
+++ b/src/liballoc/boxed.rs
@@ -66,7 +66,7 @@ use core::hash::{self, Hash};
 use core::iter::FusedIterator;
 use core::marker::{self, Unsize};
 use core::mem;
-use core::ops::{CoerceUnsized, Deref, DerefMut};
+use core::ops::{CoerceUnsized, Deref, DerefMut, Generator, GeneratorState};
 use core::ops::{BoxPlace, Boxed, InPlace, Place, Placer};
 use core::ptr::{self, Unique};
 use core::convert::From;
@@ -784,3 +784,14 @@ impl<T: ?Sized> AsMut<T> for Box<T> {
         &mut **self
     }
 }
+
+#[unstable(feature = "generator_trait", issue = "43122")]
+impl<T> Generator for Box<T>
+    where T: Generator + ?Sized
+{
+    type Yield = T::Yield;
+    type Return = T::Return;
+    fn resume(&mut self) -> GeneratorState<Self::Yield, Self::Return> {
+        (**self).resume()
+    }
+}
diff --git a/src/liballoc/heap.rs b/src/liballoc/heap.rs
index 820f2d958d9a8..b2bd9d7d8fafa 100644
--- a/src/liballoc/heap.rs
+++ b/src/liballoc/heap.rs
@@ -27,24 +27,32 @@ pub mod __core {
 
 extern "Rust" {
     #[allocator]
+    #[rustc_allocator_nounwind]
     fn __rust_alloc(size: usize, align: usize, err: *mut u8) -> *mut u8;
     #[cold]
+    #[rustc_allocator_nounwind]
     fn __rust_oom(err: *const u8) -> !;
+    #[rustc_allocator_nounwind]
     fn __rust_dealloc(ptr: *mut u8, size: usize, align: usize);
+    #[rustc_allocator_nounwind]
     fn __rust_usable_size(layout: *const u8,
                           min: *mut usize,
                           max: *mut usize);
+    #[rustc_allocator_nounwind]
     fn __rust_realloc(ptr: *mut u8,
                       old_size: usize,
                       old_align: usize,
                       new_size: usize,
                       new_align: usize,
                       err: *mut u8) -> *mut u8;
+    #[rustc_allocator_nounwind]
     fn __rust_alloc_zeroed(size: usize, align: usize, err: *mut u8) -> *mut u8;
+    #[rustc_allocator_nounwind]
     fn __rust_alloc_excess(size: usize,
                            align: usize,
                            excess: *mut usize,
                            err: *mut u8) -> *mut u8;
+    #[rustc_allocator_nounwind]
     fn __rust_realloc_excess(ptr: *mut u8,
                              old_size: usize,
                              old_align: usize,
@@ -52,11 +60,13 @@ extern "Rust" {
                              new_align: usize,
                              excess: *mut usize,
                              err: *mut u8) -> *mut u8;
+    #[rustc_allocator_nounwind]
     fn __rust_grow_in_place(ptr: *mut u8,
                             old_size: usize,
                             old_align: usize,
                             new_size: usize,
                             new_align: usize) -> u8;
+    #[rustc_allocator_nounwind]
     fn __rust_shrink_in_place(ptr: *mut u8,
                               old_size: usize,
                               old_align: usize,
diff --git a/src/liballoc/lib.rs b/src/liballoc/lib.rs
index 2d41ed648102b..dc64a787ae9ae 100644
--- a/src/liballoc/lib.rs
+++ b/src/liballoc/lib.rs
@@ -80,6 +80,7 @@
 #![cfg_attr(not(test), feature(core_float))]
 #![cfg_attr(not(test), feature(exact_size_is_empty))]
 #![cfg_attr(not(test), feature(slice_rotate))]
+#![cfg_attr(not(test), feature(generator_trait))]
 #![cfg_attr(test, feature(rand, test))]
 #![feature(allow_internal_unstable)]
 #![feature(box_patterns)]
@@ -105,6 +106,7 @@
 #![feature(pattern)]
 #![feature(placement_in_syntax)]
 #![feature(placement_new_protocol)]
+#![feature(rustc_attrs)]
 #![feature(shared)]
 #![feature(slice_get_slice)]
 #![feature(slice_patterns)]
diff --git a/src/liballoc/macros.rs b/src/liballoc/macros.rs
index 763f04fcd0dcd..43ebaa4fbdb3f 100644
--- a/src/liballoc/macros.rs
+++ b/src/liballoc/macros.rs
@@ -8,12 +8,12 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-/// Creates a `Vec` containing the arguments.
+/// Creates a [`Vec`] containing the arguments.
 ///
 /// `vec!` allows `Vec`s to be defined with the same syntax as array expressions.
 /// There are two forms of this macro:
 ///
-/// - Create a `Vec` containing a given list of elements:
+/// - Create a [`Vec`] containing a given list of elements:
 ///
 /// ```
 /// let v = vec![1, 2, 3];
@@ -22,7 +22,7 @@
 /// assert_eq!(v[2], 3);
 /// ```
 ///
-/// - Create a `Vec` from a given element and size:
+/// - Create a [`Vec`] from a given element and size:
 ///
 /// ```
 /// let v = vec![1; 3];
@@ -30,14 +30,17 @@
 /// ```
 ///
 /// Note that unlike array expressions this syntax supports all elements
-/// which implement `Clone` and the number of elements doesn't have to be
+/// which implement [`Clone`] and the number of elements doesn't have to be
 /// a constant.
 ///
-/// This will use `clone()` to duplicate an expression, so one should be careful
+/// This will use `clone` to duplicate an expression, so one should be careful
 /// using this with types having a nonstandard `Clone` implementation. For
 /// example, `vec![Rc::new(1); 5]` will create a vector of five references
 /// to the same boxed integer value, not five references pointing to independently
 /// boxed integers.
+///
+/// [`Vec`]: ../std/vec/struct.Vec.html
+/// [`Clone`]: ../std/clone/trait.Clone.html
 #[cfg(not(test))]
 #[macro_export]
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -67,10 +70,22 @@ macro_rules! vec {
     ($($x:expr,)*) => (vec![$($x),*])
 }
 
-/// Use the syntax described in `std::fmt` to create a value of type `String`.
-/// See [`std::fmt`][fmt] for more information.
+/// Creates a `String` using interpolation of runtime expressions.
+///
+/// The first argument `format!` recieves is a format string.  This must be a string
+/// literal.  The power of the formatting string is in the `{}`s contained.
+///
+/// Additional parameters passed to `format!` replace the `{}`s within the
+/// formatting string in the order given unless named or positional parameters
+/// are used, see [`std::fmt`][fmt] for more information.
+///
+/// A common use for `format!` is concatenation and interpolation of strings.
+/// The same convention is used with [`print!`] and [`write!`] macros,
+/// depending on the intended destination of the string.
 ///
 /// [fmt]: ../std/fmt/index.html
+/// [`print!`]: ../std/macro.print.html
+/// [`write!`]: ../std/macro.write.html
 ///
 /// # Panics
 ///
diff --git a/src/liballoc/string.rs b/src/liballoc/string.rs
index b1919c7c968c9..ddb23b2ef37bf 100644
--- a/src/liballoc/string.rs
+++ b/src/liballoc/string.rs
@@ -1392,11 +1392,11 @@ impl String {
     }
 
     /// Creates a splicing iterator that removes the specified range in the string,
-    /// replaces with the given string, and yields the removed chars.
-    /// The given string doesn’t need to be the same length as the range.
+    /// and replaces it with the given string.
+    /// The given string doesn't need to be the same length as the range.
     ///
-    /// Note: The element range is removed when the [`Splice`] is dropped,
-    /// even if the iterator is not consumed until the end.
+    /// Note: Unlike [`Vec::splice`], the replacement happens eagerly, and this
+    /// method does not return the removed chars.
     ///
     /// # Panics
     ///
@@ -1404,7 +1404,7 @@ impl String {
     /// boundary, or if they're out of bounds.
     ///
     /// [`char`]: ../../std/primitive.char.html
-    /// [`Splice`]: ../../std/string/struct.Splice.html
+    /// [`Vec::splice`]: ../../std/vec/struct.Vec.html#method.splice
     ///
     /// # Examples
     ///
@@ -1416,45 +1416,32 @@ impl String {
     /// let beta_offset = s.find('β').unwrap_or(s.len());
     ///
     /// // Replace the range up until the β from the string
-    /// let t: String = s.splice(..beta_offset, "Α is capital alpha; ").collect();
-    /// assert_eq!(t, "α is alpha, ");
+    /// s.splice(..beta_offset, "Α is capital alpha; ");
     /// assert_eq!(s, "Α is capital alpha; β is beta");
     /// ```
     #[unstable(feature = "splice", reason = "recently added", issue = "32310")]
-    pub fn splice<'a, 'b, R>(&'a mut self, range: R, replace_with: &'b str) -> Splice<'a, 'b>
+    pub fn splice<R>(&mut self, range: R, replace_with: &str)
         where R: RangeArgument<usize>
     {
         // Memory safety
         //
         // The String version of Splice does not have the memory safety issues
         // of the vector version. The data is just plain bytes.
-        // Because the range removal happens in Drop, if the Splice iterator is leaked,
-        // the removal will not happen.
-        let len = self.len();
-        let start = match range.start() {
-             Included(&n) => n,
-             Excluded(&n) => n + 1,
-             Unbounded => 0,
+
+        match range.start() {
+             Included(&n) => assert!(self.is_char_boundary(n)),
+             Excluded(&n) => assert!(self.is_char_boundary(n + 1)),
+             Unbounded => {},
         };
-        let end = match range.end() {
-             Included(&n) => n + 1,
-             Excluded(&n) => n,
-             Unbounded => len,
+        match range.end() {
+             Included(&n) => assert!(self.is_char_boundary(n + 1)),
+             Excluded(&n) => assert!(self.is_char_boundary(n)),
+             Unbounded => {},
         };
 
-        // Take out two simultaneous borrows. The &mut String won't be accessed
-        // until iteration is over, in Drop.
-        let self_ptr = self as *mut _;
-        // slicing does the appropriate bounds checks
-        let chars_iter = self[start..end].chars();
-
-        Splice {
-            start,
-            end,
-            iter: chars_iter,
-            string: self_ptr,
-            replace_with,
-        }
+        unsafe {
+            self.as_mut_vec()
+        }.splice(range, replace_with.bytes());
     }
 
     /// Converts this `String` into a [`Box`]`<`[`str`]`>`.
@@ -2241,61 +2228,3 @@ impl<'a> DoubleEndedIterator for Drain<'a> {
 
 #[unstable(feature = "fused", issue = "35602")]
 impl<'a> FusedIterator for Drain<'a> {}
-
-/// A splicing iterator for `String`.
-///
-/// This struct is created by the [`splice()`] method on [`String`]. See its
-/// documentation for more.
-///
-/// [`splice()`]: struct.String.html#method.splice
-/// [`String`]: struct.String.html
-#[derive(Debug)]
-#[unstable(feature = "splice", reason = "recently added", issue = "32310")]
-pub struct Splice<'a, 'b> {
-    /// Will be used as &'a mut String in the destructor
-    string: *mut String,
-    /// Start of part to remove
-    start: usize,
-    /// End of part to remove
-    end: usize,
-    /// Current remaining range to remove
-    iter: Chars<'a>,
-    replace_with: &'b str,
-}
-
-#[unstable(feature = "splice", reason = "recently added", issue = "32310")]
-unsafe impl<'a, 'b> Sync for Splice<'a, 'b> {}
-#[unstable(feature = "splice", reason = "recently added", issue = "32310")]
-unsafe impl<'a, 'b> Send for Splice<'a, 'b> {}
-
-#[unstable(feature = "splice", reason = "recently added", issue = "32310")]
-impl<'a, 'b> Drop for Splice<'a, 'b> {
-    fn drop(&mut self) {
-        unsafe {
-            let vec = (*self.string).as_mut_vec();
-            vec.splice(self.start..self.end, self.replace_with.bytes());
-        }
-    }
-}
-
-#[unstable(feature = "splice", reason = "recently added", issue = "32310")]
-impl<'a, 'b> Iterator for Splice<'a, 'b> {
-    type Item = char;
-
-    #[inline]
-    fn next(&mut self) -> Option<char> {
-        self.iter.next()
-    }
-
-    fn size_hint(&self) -> (usize, Option<usize>) {
-        self.iter.size_hint()
-    }
-}
-
-#[unstable(feature = "splice", reason = "recently added", issue = "32310")]
-impl<'a, 'b> DoubleEndedIterator for Splice<'a, 'b> {
-    #[inline]
-    fn next_back(&mut self) -> Option<char> {
-        self.iter.next_back()
-    }
-}
diff --git a/src/liballoc/tests/string.rs b/src/liballoc/tests/string.rs
index f5c124c6b4458..6aba18ddf49ff 100644
--- a/src/liballoc/tests/string.rs
+++ b/src/liballoc/tests/string.rs
@@ -442,9 +442,8 @@ fn test_drain() {
 #[test]
 fn test_splice() {
     let mut s = "Hello, world!".to_owned();
-    let t: String = s.splice(7..12, "世界").collect();
+    s.splice(7..12, "世界");
     assert_eq!(s, "Hello, 世界!");
-    assert_eq!(t, "world");
 }
 
 #[test]
@@ -457,12 +456,10 @@ fn test_splice_char_boundary() {
 #[test]
 fn test_splice_inclusive_range() {
     let mut v = String::from("12345");
-    let t: String = v.splice(2...3, "789").collect();
+    v.splice(2...3, "789");
     assert_eq!(v, "127895");
-    assert_eq!(t, "34");
-    let t2: String = v.splice(1...2, "A").collect();
+    v.splice(1...2, "A");
     assert_eq!(v, "1A895");
-    assert_eq!(t2, "27");
 }
 
 #[test]
@@ -482,24 +479,15 @@ fn test_splice_inclusive_out_of_bounds() {
 #[test]
 fn test_splice_empty() {
     let mut s = String::from("12345");
-    let t: String = s.splice(1..2, "").collect();
+    s.splice(1..2, "");
     assert_eq!(s, "1345");
-    assert_eq!(t, "2");
 }
 
 #[test]
 fn test_splice_unbounded() {
     let mut s = String::from("12345");
-    let t: String = s.splice(.., "").collect();
+    s.splice(.., "");
     assert_eq!(s, "");
-    assert_eq!(t, "12345");
-}
-
-#[test]
-fn test_splice_forget() {
-    let mut s = String::from("12345");
-    ::std::mem::forget(s.splice(2..4, "789"));
-    assert_eq!(s, "12345");
 }
 
 #[test]
diff --git a/src/liballoc/vec_deque.rs b/src/liballoc/vec_deque.rs
index bf9069200297d..00def2a1eac49 100644
--- a/src/liballoc/vec_deque.rs
+++ b/src/liballoc/vec_deque.rs
@@ -459,10 +459,12 @@ impl<T> VecDeque<T> {
     ///
     /// `i` and `j` may be equal.
     ///
-    /// Fails if there is no element with either index.
-    ///
     /// Element at index 0 is the front of the queue.
     ///
+    /// # Panics
+    ///
+    /// Panics if either index is out of bounds.
+    ///
     /// # Examples
     ///
     /// ```
diff --git a/src/liballoc_jemalloc/build.rs b/src/liballoc_jemalloc/build.rs
index 41193f6a41f89..c9bea2ecf5e9f 100644
--- a/src/liballoc_jemalloc/build.rs
+++ b/src/liballoc_jemalloc/build.rs
@@ -111,9 +111,11 @@ fn main() {
         cmd.arg("--with-jemalloc-prefix=je_");
     }
 
-    if cfg!(feature = "debug-jemalloc") {
-        cmd.arg("--enable-debug");
-    }
+    // FIXME: building with jemalloc assertions is currently broken.
+    // See <https://github.com/rust-lang/rust/issues/44152>.
+    //if cfg!(feature = "debug") {
+    //    cmd.arg("--enable-debug");
+    //}
 
     cmd.arg(format!("--host={}", build_helper::gnu_target(&target)));
     cmd.arg(format!("--build={}", build_helper::gnu_target(&host)));
diff --git a/src/libcore/array.rs b/src/libcore/array.rs
index 4b7706bac300f..6a7926fecde38 100644
--- a/src/libcore/array.rs
+++ b/src/libcore/array.rs
@@ -123,14 +123,6 @@ macro_rules! array_impls {
                 }
             }
 
-            #[stable(feature = "rust1", since = "1.0.0")]
-            #[cfg(stage0)]
-            impl<T:Copy> Clone for [T; $N] {
-                fn clone(&self) -> [T; $N] {
-                    *self
-                }
-            }
-
             #[stable(feature = "rust1", since = "1.0.0")]
             impl<T: Hash> Hash for [T; $N] {
                 fn hash<H: hash::Hasher>(&self, state: &mut H) {
diff --git a/src/libcore/clone.rs b/src/libcore/clone.rs
index 2dc51718b97b2..826420a0c001c 100644
--- a/src/libcore/clone.rs
+++ b/src/libcore/clone.rs
@@ -88,7 +88,7 @@
 /// }
 /// ```
 #[stable(feature = "rust1", since = "1.0.0")]
-#[cfg_attr(not(stage0), lang = "clone")]
+#[lang = "clone"]
 pub trait Clone : Sized {
     /// Returns a copy of the value.
     ///
@@ -130,45 +130,3 @@ pub struct AssertParamIsClone<T: Clone + ?Sized> { _field: ::marker::PhantomData
            reason = "deriving hack, should not be public",
            issue = "0")]
 pub struct AssertParamIsCopy<T: Copy + ?Sized> { _field: ::marker::PhantomData<T> }
-
-#[stable(feature = "rust1", since = "1.0.0")]
-#[cfg(stage0)]
-impl<'a, T: ?Sized> Clone for &'a T {
-    /// Returns a shallow copy of the reference.
-    #[inline]
-    fn clone(&self) -> &'a T { *self }
-}
-
-macro_rules! clone_impl {
-    ($t:ty) => {
-        #[stable(feature = "rust1", since = "1.0.0")]
-        #[cfg(stage0)]
-        impl Clone for $t {
-            /// Returns a deep copy of the value.
-            #[inline]
-            fn clone(&self) -> $t { *self }
-        }
-    }
-}
-
-clone_impl! { isize }
-clone_impl! { i8 }
-clone_impl! { i16 }
-clone_impl! { i32 }
-clone_impl! { i64 }
-clone_impl! { i128 }
-
-clone_impl! { usize }
-clone_impl! { u8 }
-clone_impl! { u16 }
-clone_impl! { u32 }
-clone_impl! { u64 }
-clone_impl! { u128 }
-
-clone_impl! { f32 }
-clone_impl! { f64 }
-
-clone_impl! { ! }
-clone_impl! { () }
-clone_impl! { bool }
-clone_impl! { char }
diff --git a/src/libcore/fmt/num.rs b/src/libcore/fmt/num.rs
index 4ca303dee43f2..8ea388fddf884 100644
--- a/src/libcore/fmt/num.rs
+++ b/src/libcore/fmt/num.rs
@@ -242,7 +242,7 @@ macro_rules! impl_Display {
                 // decode last 1 or 2 chars
                 if n < 10 {
                     curr -= 1;
-                    *buf_ptr.offset(curr) = (n as u8) + 48;
+                    *buf_ptr.offset(curr) = (n as u8) + b'0';
                 } else {
                     let d1 = n << 1;
                     curr -= 2;
diff --git a/src/libcore/intrinsics.rs b/src/libcore/intrinsics.rs
index ad776c8605ac8..607f6f3701799 100644
--- a/src/libcore/intrinsics.rs
+++ b/src/libcore/intrinsics.rs
@@ -1343,4 +1343,81 @@ extern "rust-intrinsic" {
     /// on MSVC it's `*mut [usize; 2]`. For more information see the compiler's
     /// source as well as std's catch implementation.
     pub fn try(f: fn(*mut u8), data: *mut u8, local_ptr: *mut u8) -> i32;
+
+    /// Computes the byte offset that needs to be applied to `ptr` in order to
+    /// make it aligned to `align`.
+    /// If it is not possible to align `ptr`, the implementation returns
+    /// `usize::max_value()`.
+    ///
+    /// There are no guarantees whatsover that offsetting the pointer will not
+    /// overflow or go beyond the allocation that `ptr` points into.
+    /// It is up to the caller to ensure that the returned offset is correct
+    /// in all terms other than alignment.
+    ///
+    /// # Examples
+    ///
+    /// Accessing adjacent `u8` as `u16`
+    ///
+    /// ```
+    /// # #![feature(core_intrinsics)]
+    /// # fn foo(n: usize) {
+    /// # use std::intrinsics::align_offset;
+    /// # use std::mem::align_of;
+    /// # unsafe {
+    /// let x = [5u8, 6u8, 7u8, 8u8, 9u8];
+    /// let ptr = &x[n] as *const u8;
+    /// let offset = align_offset(ptr as *const (), align_of::<u16>());
+    /// if offset < x.len() - n - 1 {
+    ///     let u16_ptr = ptr.offset(offset as isize) as *const u16;
+    ///     assert_ne!(*u16_ptr, 500);
+    /// } else {
+    ///     // while the pointer can be aligned via `offset`, it would point
+    ///     // outside the allocation
+    /// }
+    /// # } }
+    /// ```
+    #[cfg(not(stage0))]
+    pub fn align_offset(ptr: *const (), align: usize) -> usize;
+}
+
+#[cfg(stage0)]
+/// Computes the byte offset that needs to be applied to `ptr` in order to
+/// make it aligned to `align`.
+/// If it is not possible to align `ptr`, the implementation returns
+/// `usize::max_value()`.
+///
+/// There are no guarantees whatsover that offsetting the pointer will not
+/// overflow or go beyond the allocation that `ptr` points into.
+/// It is up to the caller to ensure that the returned offset is correct
+/// in all terms other than alignment.
+///
+/// # Examples
+///
+/// Accessing adjacent `u8` as `u16`
+///
+/// ```
+/// # #![feature(core_intrinsics)]
+/// # fn foo(n: usize) {
+/// # use std::intrinsics::align_offset;
+/// # use std::mem::align_of;
+/// # unsafe {
+/// let x = [5u8, 6u8, 7u8, 8u8, 9u8];
+/// let ptr = &x[n] as *const u8;
+/// let offset = align_offset(ptr as *const (), align_of::<u16>());
+/// if offset < x.len() - n - 1 {
+///     let u16_ptr = ptr.offset(offset as isize) as *const u16;
+///     assert_ne!(*u16_ptr, 500);
+/// } else {
+///     // while the pointer can be aligned via `offset`, it would point
+///     // outside the allocation
+/// }
+/// # } }
+/// ```
+pub unsafe fn align_offset(ptr: *const (), align: usize) -> usize {
+    let offset = ptr as usize % align;
+    if offset == 0 {
+        0
+    } else {
+        align - offset
+    }
 }
diff --git a/src/libcore/macros.rs b/src/libcore/macros.rs
index 684b81a27f82e..ce183389a8083 100644
--- a/src/libcore/macros.rs
+++ b/src/libcore/macros.rs
@@ -8,16 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#[macro_export]
-// This stability attribute is totally useless.
-#[stable(feature = "rust1", since = "1.0.0")]
-#[cfg(stage0)]
-macro_rules! __rust_unstable_column {
-    () => {
-        column!()
-    }
-}
-
 /// Entry point of thread panic, for details, see std::macros
 #[macro_export]
 #[allow_internal_unstable]
@@ -62,11 +52,13 @@ macro_rules! panic {
 /// # Custom Messages
 ///
 /// This macro has a second form, where a custom panic message can
-/// be provided with or without arguments for formatting.
+/// be provided with or without arguments for formatting.  See [`std::fmt`]
+/// for syntax for this form.
 ///
 /// [`panic!`]: macro.panic.html
 /// [`debug_assert!`]: macro.debug_assert.html
-/// [testing]: ../book/first-edition/testing.html
+/// [testing]: ../book/second-edition/ch11-01-writing-tests.html#checking-results-with-the-assert-macro
+/// [`std::fmt`]: ../std/fmt/index.html
 ///
 /// # Examples
 ///
@@ -252,13 +244,15 @@ macro_rules! debug_assert {
 /// On panic, this macro will print the values of the expressions with their
 /// debug representations.
 ///
-/// Unlike `assert_eq!`, `debug_assert_eq!` statements are only enabled in non
+/// Unlike [`assert_eq!`], `debug_assert_eq!` statements are only enabled in non
 /// optimized builds by default. An optimized build will omit all
 /// `debug_assert_eq!` statements unless `-C debug-assertions` is passed to the
 /// compiler. This makes `debug_assert_eq!` useful for checks that are too
 /// expensive to be present in a release build but may be helpful during
 /// development.
 ///
+/// [`assert_eq!`]: ../std/macro.assert_eq.html
+///
 /// # Examples
 ///
 /// ```
@@ -277,13 +271,15 @@ macro_rules! debug_assert_eq {
 /// On panic, this macro will print the values of the expressions with their
 /// debug representations.
 ///
-/// Unlike `assert_ne!`, `debug_assert_ne!` statements are only enabled in non
+/// Unlike [`assert_ne!`], `debug_assert_ne!` statements are only enabled in non
 /// optimized builds by default. An optimized build will omit all
 /// `debug_assert_ne!` statements unless `-C debug-assertions` is passed to the
 /// compiler. This makes `debug_assert_ne!` useful for checks that are too
 /// expensive to be present in a release build but may be helpful during
 /// development.
 ///
+/// [`assert_ne!`]: ../std/macro.assert_ne.html
+///
 /// # Examples
 ///
 /// ```
@@ -300,10 +296,9 @@ macro_rules! debug_assert_ne {
 /// Helper macro for reducing boilerplate code for matching `Result` together
 /// with converting downstream errors.
 ///
-/// Prefer using `?` syntax to `try!`. `?` is built in to the language and is
-/// more succinct than `try!`. It is the standard method for error propagation.
+/// The `?` operator was added to replace `try!` and should be used instead.
 ///
-/// `try!` matches the given `Result`. In case of the `Ok` variant, the
+/// `try!` matches the given [`Result`]. In case of the `Ok` variant, the
 /// expression has the value of the wrapped value.
 ///
 /// In case of the `Err` variant, it retrieves the inner error. `try!` then
@@ -312,7 +307,9 @@ macro_rules! debug_assert_ne {
 /// error is then immediately returned.
 ///
 /// Because of the early return, `try!` can only be used in functions that
-/// return `Result`.
+/// return [`Result`].
+///
+/// [`Result`]: ../std/result/enum.Result.html
 ///
 /// # Examples
 ///
@@ -331,12 +328,19 @@ macro_rules! debug_assert_ne {
 ///     }
 /// }
 ///
+/// // The prefered method of quick returning Errors
+/// fn write_to_file_question() -> Result<(), MyError> {
+///     let mut file = File::create("my_best_friends.txt")?;
+///     Ok(())
+/// }
+///
+/// // The previous method of quick returning Errors
 /// fn write_to_file_using_try() -> Result<(), MyError> {
 ///     let mut file = try!(File::create("my_best_friends.txt"));
 ///     try!(file.write_all(b"This is a list of my best friends."));
-///     println!("I wrote to the file");
 ///     Ok(())
 /// }
+///
 /// // This is equivalent to:
 /// fn write_to_file_using_match() -> Result<(), MyError> {
 ///     let mut file = try!(File::create("my_best_friends.txt"));
@@ -344,7 +348,6 @@ macro_rules! debug_assert_ne {
 ///         Ok(v) => v,
 ///         Err(e) => return Err(From::from(e)),
 ///     }
-///     println!("I wrote to the file");
 ///     Ok(())
 /// }
 /// ```
@@ -365,7 +368,7 @@ macro_rules! try {
 /// formatted according to the specified format string and the result will be passed to the writer.
 /// The writer may be any value with a `write_fmt` method; generally this comes from an
 /// implementation of either the [`std::fmt::Write`] or the [`std::io::Write`] trait. The macro
-/// returns whatever the 'write_fmt' method returns; commonly a [`std::fmt::Result`], or an
+/// returns whatever the `write_fmt` method returns; commonly a [`std::fmt::Result`], or an
 /// [`io::Result`].
 ///
 /// See [`std::fmt`] for more information on the format string syntax.
@@ -470,10 +473,20 @@ macro_rules! writeln {
 /// * Loops that dynamically terminate.
 /// * Iterators that dynamically terminate.
 ///
+/// If the determination that the code is unreachable proves incorrect, the
+/// program immediately terminates with a [`panic!`].  The function [`unreachable`],
+/// which belongs to the [`std::intrinsics`] module, informs the compilier to
+/// optimize the code out of the release version entirely.
+///
+/// [`panic!`]:  ../std/macro.panic.html
+/// [`unreachable`]: ../std/intrinsics/fn.unreachable.html
+/// [`std::intrinsics`]: ../std/intrinsics/index.html
+///
 /// # Panics
 ///
-/// This will always [panic!](macro.panic.html)
+/// This will always [`panic!`]
 ///
+/// [`panic!`]: ../std/macro.panic.html
 /// # Examples
 ///
 /// Match arms:
@@ -516,13 +529,18 @@ macro_rules! unreachable {
     });
 }
 
-/// A standardized placeholder for marking unfinished code. It panics with the
-/// message `"not yet implemented"` when executed.
+/// A standardized placeholder for marking unfinished code.
+///
+/// It panics with the message `"not yet implemented"` when executed.
 ///
 /// This can be useful if you are prototyping and are just looking to have your
 /// code typecheck, or if you're implementing a trait that requires multiple
 /// methods, and you're only planning on using one of them.
 ///
+/// # Panics
+///
+/// This macro always panics.
+///
 /// # Examples
 ///
 /// Here's an example of some in-progress code. We have a trait `Foo`:
diff --git a/src/libcore/mem.rs b/src/libcore/mem.rs
index 4b866cab1eae2..a57d835528980 100644
--- a/src/libcore/mem.rs
+++ b/src/libcore/mem.rs
@@ -188,26 +188,6 @@ pub fn forget<T>(t: T) {
 /// ```
 #[inline]
 #[stable(feature = "rust1", since = "1.0.0")]
-#[cfg(stage0)]
-pub fn size_of<T>() -> usize {
-    unsafe { intrinsics::size_of::<T>() }
-}
-
-/// Returns the size of a type in bytes.
-///
-/// More specifically, this is the offset in bytes between successive
-/// items of the same type, including alignment padding.
-///
-/// # Examples
-///
-/// ```
-/// use std::mem;
-///
-/// assert_eq!(4, mem::size_of::<i32>());
-/// ```
-#[inline]
-#[stable(feature = "rust1", since = "1.0.0")]
-#[cfg(not(stage0))]
 pub const fn size_of<T>() -> usize {
     unsafe { intrinsics::size_of::<T>() }
 }
@@ -299,29 +279,6 @@ pub fn min_align_of_val<T: ?Sized>(val: &T) -> usize {
 /// ```
 #[inline]
 #[stable(feature = "rust1", since = "1.0.0")]
-#[cfg(stage0)]
-pub fn align_of<T>() -> usize {
-    unsafe { intrinsics::min_align_of::<T>() }
-}
-
-/// Returns the [ABI]-required minimum alignment of a type.
-///
-/// Every reference to a value of the type `T` must be a multiple of this number.
-///
-/// This is the alignment used for struct fields. It may be smaller than the preferred alignment.
-///
-/// [ABI]: https://en.wikipedia.org/wiki/Application_binary_interface
-///
-/// # Examples
-///
-/// ```
-/// use std::mem;
-///
-/// assert_eq!(4, mem::align_of::<i32>());
-/// ```
-#[inline]
-#[stable(feature = "rust1", since = "1.0.0")]
-#[cfg(not(stage0))]
 pub const fn align_of<T>() -> usize {
     unsafe { intrinsics::min_align_of::<T>() }
 }
@@ -754,39 +711,39 @@ pub unsafe fn transmute_copy<T, U>(src: &T) -> U {
 /// Opaque type representing the discriminant of an enum.
 ///
 /// See the `discriminant` function in this module for more information.
-#[unstable(feature = "discriminant_value", reason = "recently added, follows RFC", issue = "24263")]
+#[stable(feature = "discriminant_value", since = "1.22.0")]
 pub struct Discriminant<T>(u64, PhantomData<*const T>);
 
 // N.B. These trait implementations cannot be derived because we don't want any bounds on T.
 
-#[unstable(feature = "discriminant_value", reason = "recently added, follows RFC", issue = "24263")]
+#[stable(feature = "discriminant_value", since = "1.22.0")]
 impl<T> Copy for Discriminant<T> {}
 
-#[unstable(feature = "discriminant_value", reason = "recently added, follows RFC", issue = "24263")]
+#[stable(feature = "discriminant_value", since = "1.22.0")]
 impl<T> clone::Clone for Discriminant<T> {
     fn clone(&self) -> Self {
         *self
     }
 }
 
-#[unstable(feature = "discriminant_value", reason = "recently added, follows RFC", issue = "24263")]
+#[stable(feature = "discriminant_value", since = "1.22.0")]
 impl<T> cmp::PartialEq for Discriminant<T> {
     fn eq(&self, rhs: &Self) -> bool {
         self.0 == rhs.0
     }
 }
 
-#[unstable(feature = "discriminant_value", reason = "recently added, follows RFC", issue = "24263")]
+#[stable(feature = "discriminant_value", since = "1.22.0")]
 impl<T> cmp::Eq for Discriminant<T> {}
 
-#[unstable(feature = "discriminant_value", reason = "recently added, follows RFC", issue = "24263")]
+#[stable(feature = "discriminant_value", since = "1.22.0")]
 impl<T> hash::Hash for Discriminant<T> {
     fn hash<H: hash::Hasher>(&self, state: &mut H) {
         self.0.hash(state);
     }
 }
 
-#[unstable(feature = "discriminant_value", reason = "recently added, follows RFC", issue = "24263")]
+#[stable(feature = "discriminant_value", since = "1.22.0")]
 impl<T> fmt::Debug for Discriminant<T> {
     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
         fmt.debug_tuple("Discriminant")
@@ -811,7 +768,6 @@ impl<T> fmt::Debug for Discriminant<T> {
 /// the actual data:
 ///
 /// ```
-/// #![feature(discriminant_value)]
 /// use std::mem;
 ///
 /// enum Foo { A(&'static str), B(i32), C(i32) }
@@ -820,7 +776,7 @@ impl<T> fmt::Debug for Discriminant<T> {
 /// assert!(mem::discriminant(&Foo::B(1))     == mem::discriminant(&Foo::B(2)));
 /// assert!(mem::discriminant(&Foo::B(3))     != mem::discriminant(&Foo::C(3)));
 /// ```
-#[unstable(feature = "discriminant_value", reason = "recently added, follows RFC", issue = "24263")]
+#[stable(feature = "discriminant_value", since = "1.22.0")]
 pub fn discriminant<T>(v: &T) -> Discriminant<T> {
     unsafe {
         Discriminant(intrinsics::discriminant_value(v), PhantomData)
diff --git a/src/libcore/num/f32.rs b/src/libcore/num/f32.rs
index 5068375368466..43d38926c9718 100644
--- a/src/libcore/num/f32.rs
+++ b/src/libcore/num/f32.rs
@@ -10,8 +10,6 @@
 
 //! Operations and constants for 32-bits floats (`f32` type)
 
-#![cfg_attr(stage0, allow(overflowing_literals))]
-
 #![stable(feature = "rust1", since = "1.0.0")]
 
 use intrinsics;
diff --git a/src/libcore/ops/generator.rs b/src/libcore/ops/generator.rs
new file mode 100644
index 0000000000000..798c182bc6e38
--- /dev/null
+++ b/src/libcore/ops/generator.rs
@@ -0,0 +1,131 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+/// The result of a generator resumption.
+///
+/// This enum is returned from the `Generator::resume` method and indicates the
+/// possible return values of a generator. Currently this corresponds to either
+/// a suspension point (`Yielded`) or a termination point (`Complete`).
+#[derive(Clone, Copy, PartialEq, PartialOrd, Eq, Ord, Debug, Hash)]
+#[cfg_attr(not(stage0), lang = "generator_state")]
+#[unstable(feature = "generator_trait", issue = "43122")]
+pub enum GeneratorState<Y, R> {
+    /// The generator suspended with a value.
+    ///
+    /// This state indicates that a generator has been suspended, and typically
+    /// corresponds to a `yield` statement. The value provided in this variant
+    /// corresponds to the expression passed to `yield` and allows generators to
+    /// provide a value each time they yield.
+    Yielded(Y),
+
+    /// The generator completed with a return value.
+    ///
+    /// This state indicates that a generator has finished execution with the
+    /// provided value. Once a generator has returned `Complete` it is
+    /// considered a programmer error to call `resume` again.
+    Complete(R),
+}
+
+/// The trait implemented by builtin generator types.
+///
+/// Generators, also commonly referred to as coroutines, are currently an
+/// experimental language feature in Rust. Added in [RFC 2033] generators are
+/// currently intended to primarily provide a building block for async/await
+/// syntax but will likely extend to also providing an ergonomic definition for
+/// iterators and other primitives.
+///
+/// The syntax and semantics for generators is unstable and will require a
+/// further RFC for stabilization. At this time, though, the syntax is
+/// closure-like:
+///
+/// ```rust
+/// #![feature(generators, generator_trait)]
+///
+/// use std::ops::{Generator, GeneratorState};
+///
+/// fn main() {
+///     let mut generator = || {
+///         yield 1;
+///         return "foo"
+///     };
+///
+///     match generator.resume() {
+///         GeneratorState::Yielded(1) => {}
+///         _ => panic!("unexpected return from resume"),
+///     }
+///     match generator.resume() {
+///         GeneratorState::Complete("foo") => {}
+///         _ => panic!("unexpected return from resume"),
+///     }
+/// }
+/// ```
+///
+/// More documentation of generators can be found in the unstable book.
+///
+/// [RFC 2033]: https://github.com/rust-lang/rfcs/pull/2033
+#[cfg_attr(not(stage0), lang = "generator")]
+#[unstable(feature = "generator_trait", issue = "43122")]
+#[fundamental]
+pub trait Generator {
+    /// The type of value this generator yields.
+    ///
+    /// This associated type corresponds to the `yield` expression and the
+    /// values which are allowed to be returned each time a generator yields.
+    /// For example an iterator-as-a-generator would likely have this type as
+    /// `T`, the type being iterated over.
+    type Yield;
+
+    /// The type of value this generator returns.
+    ///
+    /// This corresponds to the type returned from a generator either with a
+    /// `return` statement or implicitly as the last expression of a generator
+    /// literal. For example futures would use this as `Result<T, E>` as it
+    /// represents a completed future.
+    type Return;
+
+    /// Resumes the execution of this generator.
+    ///
+    /// This function will resume execution of the generator or start execution
+    /// if it hasn't already. This call will return back into the generator's
+    /// last suspension point, resuming execution from the latest `yield`. The
+    /// generator will continue executing until it either yields or returns, at
+    /// which point this function will return.
+    ///
+    /// # Return value
+    ///
+    /// The `GeneratorState` enum returned from this function indicates what
+    /// state the generator is in upon returning. If the `Yielded` variant is
+    /// returned then the generator has reached a suspension point and a value
+    /// has been yielded out. Generators in this state are available for
+    /// resumption at a later point.
+    ///
+    /// If `Complete` is returned then the generator has completely finished
+    /// with the value provided. It is invalid for the generator to be resumed
+    /// again.
+    ///
+    /// # Panics
+    ///
+    /// This function may panic if it is called after the `Complete` variant has
+    /// been returned previously. While generator literals in the language are
+    /// guaranteed to panic on resuming after `Complete`, this is not guaranteed
+    /// for all implementations of the `Generator` trait.
+    fn resume(&mut self) -> GeneratorState<Self::Yield, Self::Return>;
+}
+
+#[unstable(feature = "generator_trait", issue = "43122")]
+impl<'a, T> Generator for &'a mut T
+    where T: Generator + ?Sized
+{
+    type Yield = T::Yield;
+    type Return = T::Return;
+    fn resume(&mut self) -> GeneratorState<Self::Yield, Self::Return> {
+        (**self).resume()
+    }
+}
diff --git a/src/libcore/ops/mod.rs b/src/libcore/ops/mod.rs
index b5e6912b10d6e..8975b680ca7fa 100644
--- a/src/libcore/ops/mod.rs
+++ b/src/libcore/ops/mod.rs
@@ -159,6 +159,7 @@ mod bit;
 mod deref;
 mod drop;
 mod function;
+mod generator;
 mod index;
 mod place;
 mod range;
@@ -196,6 +197,9 @@ pub use self::range::{RangeInclusive, RangeToInclusive};
 #[unstable(feature = "try_trait", issue = "42327")]
 pub use self::try::Try;
 
+#[unstable(feature = "generator_trait", issue = "43122")]
+pub use self::generator::{Generator, GeneratorState};
+
 #[unstable(feature = "placement_new_protocol", issue = "27779")]
 pub use self::place::{Place, Placer, InPlace, Boxed, BoxPlace};
 
diff --git a/src/libcore/ops/try.rs b/src/libcore/ops/try.rs
index 78326c3e6391a..e788b66a1ec82 100644
--- a/src/libcore/ops/try.rs
+++ b/src/libcore/ops/try.rs
@@ -15,8 +15,24 @@
 /// extracting those success or failure values from an existing instance and
 /// creating a new instance from a success or failure value.
 #[unstable(feature = "try_trait", issue = "42327")]
-#[rustc_on_unimplemented = "the `?` operator can only be used in a function that returns `Result` \
-                            (or another type that implements `{Try}`)"]
+#[cfg_attr(stage0,
+           rustc_on_unimplemented = "the `?` operator can only be used in a \
+                                     function that returns `Result` \
+                                     (or another type that implements `{Try}`)")]
+#[cfg_attr(not(stage0),
+           rustc_on_unimplemented(
+               on(all(
+                   any(from_method="from_error", from_method="from_ok"),
+                   from_desugaring="?"),
+                  message="the `?` operator can only be used in a \
+                           function that returns `Result` \
+                           (or another type that implements `{Try}`)",
+                  label="cannot use the `?` operator in a function that returns `{Self}`"),
+               on(all(from_method="into_result", from_desugaring="?"),
+                  message="the `?` operator can only be applied to values \
+                           that implement `{Try}`",
+                  label="the `?` operator cannot be applied to type `{Self}`")
+))]
 pub trait Try {
     /// The type of this value when viewed as successful.
     #[unstable(feature = "try_trait", issue = "42327")]
diff --git a/src/libcore/option.rs b/src/libcore/option.rs
index aecf2ee9325ee..138e04c7737e0 100644
--- a/src/libcore/option.rs
+++ b/src/libcore/option.rs
@@ -774,6 +774,26 @@ impl<'a, T: Clone> Option<&'a T> {
     }
 }
 
+impl<'a, T: Clone> Option<&'a mut T> {
+    /// Maps an `Option<&mut T>` to an `Option<T>` by cloning the contents of the
+    /// option.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(option_ref_mut_cloned)]
+    /// let mut x = 12;
+    /// let opt_x = Some(&mut x);
+    /// assert_eq!(opt_x, Some(&mut 12));
+    /// let cloned = opt_x.cloned();
+    /// assert_eq!(cloned, Some(12));
+    /// ```
+    #[unstable(feature = "option_ref_mut_cloned", issue = "43738")]
+    pub fn cloned(self) -> Option<T> {
+        self.map(|t| t.clone())
+    }
+}
+
 impl<T: Default> Option<T> {
     /// Returns the contained value or a default
     ///
diff --git a/src/libcore/ptr.rs b/src/libcore/ptr.rs
index 63e9373e93606..2e42e0dfd550d 100644
--- a/src/libcore/ptr.rs
+++ b/src/libcore/ptr.rs
@@ -875,36 +875,9 @@ pub fn eq<T: ?Sized>(a: *const T, b: *const T) -> bool {
     a == b
 }
 
-#[stable(feature = "rust1", since = "1.0.0")]
-#[cfg(stage0)]
-impl<T: ?Sized> Clone for *const T {
-    #[inline]
-    fn clone(&self) -> *const T {
-        *self
-    }
-}
-
-#[stable(feature = "rust1", since = "1.0.0")]
-#[cfg(stage0)]
-impl<T: ?Sized> Clone for *mut T {
-    #[inline]
-    fn clone(&self) -> *mut T {
-        *self
-    }
-}
-
 // Impls for function pointers
 macro_rules! fnptr_impls_safety_abi {
     ($FnTy: ty, $($Arg: ident),*) => {
-        #[stable(feature = "rust1", since = "1.0.0")]
-        #[cfg(stage0)]
-        impl<Ret, $($Arg),*> Clone for $FnTy {
-            #[inline]
-            fn clone(&self) -> Self {
-                *self
-            }
-        }
-
         #[stable(feature = "fnptr_impls", since = "1.4.0")]
         impl<Ret, $($Arg),*> PartialEq for $FnTy {
             #[inline]
diff --git a/src/libcore/str/mod.rs b/src/libcore/str/mod.rs
index a5f6e49a53b4f..62e84c9ebd017 100644
--- a/src/libcore/str/mod.rs
+++ b/src/libcore/str/mod.rs
@@ -23,6 +23,7 @@ use fmt;
 use iter::{Map, Cloned, FusedIterator};
 use slice::{self, SliceIndex};
 use mem;
+use intrinsics::align_offset;
 
 pub mod pattern;
 
@@ -1468,7 +1469,10 @@ fn run_utf8_validation(v: &[u8]) -> Result<(), Utf8Error> {
             // When the pointer is aligned, read 2 words of data per iteration
             // until we find a word containing a non-ascii byte.
             let ptr = v.as_ptr();
-            let align = (ptr as usize + index) & (usize_bytes - 1);
+            let align = unsafe {
+                // the offset is safe, because `index` is guaranteed inbounds
+                align_offset(ptr.offset(index as isize) as *const (), usize_bytes)
+            };
             if align == 0 {
                 while index < blocks_end {
                     unsafe {
diff --git a/src/libcore/tuple.rs b/src/libcore/tuple.rs
index 555843dba418e..4c5370194fecb 100644
--- a/src/libcore/tuple.rs
+++ b/src/libcore/tuple.rs
@@ -21,14 +21,6 @@ macro_rules! tuple_impls {
         }
     )+) => {
         $(
-            #[stable(feature = "rust1", since = "1.0.0")]
-            #[cfg(stage0)]
-            impl<$($T:Clone),+> Clone for ($($T,)+) {
-                fn clone(&self) -> ($($T,)+) {
-                    ($(self.$idx.clone(),)+)
-                }
-            }
-
             #[stable(feature = "rust1", since = "1.0.0")]
             impl<$($T:PartialEq),+> PartialEq for ($($T,)+) where last_type!($($T,)+): ?Sized {
                 #[inline]
diff --git a/src/liblibc b/src/liblibc
index 2a5b50b7f7f53..04a5e75c99dc9 160000
--- a/src/liblibc
+++ b/src/liblibc
@@ -1 +1 @@
-Subproject commit 2a5b50b7f7f539a0fd201331d6c1e0534aa332f5
+Subproject commit 04a5e75c99dc92afab490c38fcbbeac9b4bc8104
diff --git a/src/libproc_macro/Cargo.toml b/src/libproc_macro/Cargo.toml
index 1b5141773a967..cfd83e348a8e2 100644
--- a/src/libproc_macro/Cargo.toml
+++ b/src/libproc_macro/Cargo.toml
@@ -10,3 +10,4 @@ crate-type = ["dylib"]
 [dependencies]
 syntax = { path = "../libsyntax" }
 syntax_pos = { path = "../libsyntax_pos" }
+rustc_errors = { path = "../librustc_errors" }
diff --git a/src/libproc_macro/diagnostic.rs b/src/libproc_macro/diagnostic.rs
new file mode 100644
index 0000000000000..c39aec896e6b4
--- /dev/null
+++ b/src/libproc_macro/diagnostic.rs
@@ -0,0 +1,134 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use Span;
+
+use rustc_errors as rustc;
+
+/// An enum representing a diagnostic level.
+#[unstable(feature = "proc_macro", issue = "38356")]
+#[derive(Copy, Clone, Debug)]
+pub enum Level {
+    /// An error.
+    Error,
+    /// A warning.
+    Warning,
+    /// A note.
+    Note,
+    /// A help message.
+    Help,
+    #[doc(hidden)]
+    __Nonexhaustive,
+}
+
+/// A structure representing a diagnostic message and associated children
+/// messages.
+#[unstable(feature = "proc_macro", issue = "38356")]
+#[derive(Clone, Debug)]
+pub struct Diagnostic {
+    level: Level,
+    message: String,
+    span: Option<Span>,
+    children: Vec<Diagnostic>
+}
+
+macro_rules! diagnostic_child_methods {
+    ($spanned:ident, $regular:ident, $level:expr) => (
+        /// Add a new child diagnostic message to `self` with the level
+        /// identified by this methods name with the given `span` and `message`.
+        #[unstable(feature = "proc_macro", issue = "38356")]
+        pub fn $spanned<T: Into<String>>(mut self, span: Span, message: T) -> Diagnostic {
+            self.children.push(Diagnostic::spanned(span, $level, message));
+            self
+        }
+
+        /// Add a new child diagnostic message to `self` with the level
+        /// identified by this method's name with the given `message`.
+        #[unstable(feature = "proc_macro", issue = "38356")]
+        pub fn $regular<T: Into<String>>(mut self, message: T) -> Diagnostic {
+            self.children.push(Diagnostic::new($level, message));
+            self
+        }
+    )
+}
+
+impl Diagnostic {
+    /// Create a new diagnostic with the given `level` and `message`.
+    #[unstable(feature = "proc_macro", issue = "38356")]
+    pub fn new<T: Into<String>>(level: Level, message: T) -> Diagnostic {
+        Diagnostic {
+            level: level,
+            message: message.into(),
+            span: None,
+            children: vec![]
+        }
+    }
+
+    /// Create a new diagnostic with the given `level` and `message` pointing to
+    /// the given `span`.
+    #[unstable(feature = "proc_macro", issue = "38356")]
+    pub fn spanned<T: Into<String>>(span: Span, level: Level, message: T) -> Diagnostic {
+        Diagnostic {
+            level: level,
+            message: message.into(),
+            span: Some(span),
+            children: vec![]
+        }
+    }
+
+    diagnostic_child_methods!(span_error, error, Level::Error);
+    diagnostic_child_methods!(span_warning, warning, Level::Warning);
+    diagnostic_child_methods!(span_note, note, Level::Note);
+    diagnostic_child_methods!(span_help, help, Level::Help);
+
+    /// Returns the diagnostic `level` for `self`.
+    #[unstable(feature = "proc_macro", issue = "38356")]
+    pub fn level(&self) -> Level {
+        self.level
+    }
+
+    /// Emit the diagnostic.
+    #[unstable(feature = "proc_macro", issue = "38356")]
+    pub fn emit(self) {
+        ::__internal::with_sess(move |(sess, _)| {
+            let handler = &sess.span_diagnostic;
+            let level = __internal::level_to_internal_level(self.level);
+            let mut diag = rustc::DiagnosticBuilder::new(handler, level, &*self.message);
+
+            if let Some(span) = self.span {
+                diag.set_span(span.0);
+            }
+
+            for child in self.children {
+                let span = child.span.map(|s| s.0);
+                let level = __internal::level_to_internal_level(child.level);
+                diag.sub(level, &*child.message, span);
+            }
+
+            diag.emit();
+        });
+    }
+}
+
+#[unstable(feature = "proc_macro_internals", issue = "27812")]
+#[doc(hidden)]
+pub mod __internal {
+    use super::{Level, rustc};
+
+    pub fn level_to_internal_level(level: Level) -> rustc::Level {
+        match level {
+            Level::Error => rustc::Level::Error,
+            Level::Warning => rustc::Level::Warning,
+            Level::Note => rustc::Level::Note,
+            Level::Help => rustc::Level::Help,
+            Level::__Nonexhaustive => unreachable!("Level::__Nonexhaustive")
+        }
+    }
+}
diff --git a/src/libproc_macro/lib.rs b/src/libproc_macro/lib.rs
index 3f425c24a9143..e403e2a00c9e3 100644
--- a/src/libproc_macro/lib.rs
+++ b/src/libproc_macro/lib.rs
@@ -42,6 +42,12 @@
 #[macro_use]
 extern crate syntax;
 extern crate syntax_pos;
+extern crate rustc_errors;
+
+mod diagnostic;
+
+#[unstable(feature = "proc_macro", issue = "38356")]
+pub use diagnostic::{Diagnostic, Level};
 
 use std::{ascii, fmt, iter};
 use std::str::FromStr;
@@ -89,10 +95,7 @@ impl FromStr for TokenStream {
             // notify the expansion info that it is unhygienic
             let mark = Mark::fresh(mark);
             mark.set_expn_info(expn_info);
-            let span = syntax_pos::Span {
-                ctxt: SyntaxContext::empty().apply_mark(mark),
-                ..call_site
-            };
+            let span = call_site.with_ctxt(SyntaxContext::empty().apply_mark(mark));
             let stream = parse::parse_stream_from_source_str(name, src, sess, Some(span));
             Ok(__internal::token_stream_wrap(stream))
         })
@@ -177,10 +180,10 @@ pub struct Span(syntax_pos::Span);
 #[unstable(feature = "proc_macro", issue = "38356")]
 impl Default for Span {
     fn default() -> Span {
-        ::__internal::with_sess(|(_, mark)| Span(syntax_pos::Span {
-            ctxt: SyntaxContext::empty().apply_mark(mark),
-            ..mark.expn_info().unwrap().call_site
-        }))
+        ::__internal::with_sess(|(_, mark)| {
+            let call_site = mark.expn_info().unwrap().call_site;
+            Span(call_site.with_ctxt(SyntaxContext::empty().apply_mark(mark)))
+        })
     }
 }
 
@@ -191,12 +194,28 @@ pub fn quote_span(span: Span) -> TokenStream {
     TokenStream(quote::Quote::quote(&span.0))
 }
 
+macro_rules! diagnostic_method {
+    ($name:ident, $level:expr) => (
+        /// Create a new `Diagnostic` with the given `message` at the span
+        /// `self`.
+        #[unstable(feature = "proc_macro", issue = "38356")]
+        pub fn $name<T: Into<String>>(self, message: T) -> Diagnostic {
+            Diagnostic::spanned(self, $level, message)
+        }
+    )
+}
+
 impl Span {
     /// The span of the invocation of the current procedural macro.
     #[unstable(feature = "proc_macro", issue = "38356")]
     pub fn call_site() -> Span {
         ::__internal::with_sess(|(_, mark)| Span(mark.expn_info().unwrap().call_site))
     }
+
+    diagnostic_method!(error, Level::Error);
+    diagnostic_method!(warning, Level::Warning);
+    diagnostic_method!(note, Level::Note);
+    diagnostic_method!(help, Level::Help);
 }
 
 /// A single token or a delimited sequence of token trees (e.g. `[1, (), ..]`).
@@ -570,7 +589,7 @@ impl TokenTree {
                 }).into();
             },
             TokenNode::Term(symbol) => {
-                let ident = ast::Ident { name: symbol.0, ctxt: self.span.0.ctxt };
+                let ident = ast::Ident { name: symbol.0, ctxt: self.span.0.ctxt() };
                 let token =
                     if symbol.0.as_str().starts_with("'") { Lifetime(ident) } else { Ident(ident) };
                 return TokenTree::Token(self.span.0, token).into();
diff --git a/src/librustc/cfg/construct.rs b/src/librustc/cfg/construct.rs
index fa6b78045ffad..ff2c36416bfd2 100644
--- a/src/librustc/cfg/construct.rs
+++ b/src/librustc/cfg/construct.rs
@@ -10,9 +10,8 @@
 
 use rustc_data_structures::graph;
 use cfg::*;
-use middle::region::CodeExtent;
+use middle::region;
 use ty::{self, TyCtxt};
-use syntax::ast;
 use syntax::ptr::P;
 
 use hir::{self, PatKind};
@@ -30,13 +29,13 @@ struct CFGBuilder<'a, 'tcx: 'a> {
 
 #[derive(Copy, Clone)]
 struct BlockScope {
-    block_expr_id: ast::NodeId, // id of breakable block expr node
+    block_expr_id: hir::ItemLocalId, // id of breakable block expr node
     break_index: CFGIndex, // where to go on `break`
 }
 
 #[derive(Copy, Clone)]
 struct LoopScope {
-    loop_id: ast::NodeId,     // id of loop/while node
+    loop_id: hir::ItemLocalId,     // id of loop/while node
     continue_index: CFGIndex, // where to go on a `loop`
     break_index: CFGIndex,    // where to go on a `break`
 }
@@ -70,6 +69,7 @@ pub fn construct<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
     cfg_builder.add_contained_edge(body_exit, fn_exit);
     let CFGBuilder { graph, .. } = cfg_builder;
     CFG {
+        owner_def_id,
         graph,
         entry,
         exit: fn_exit,
@@ -79,10 +79,10 @@ pub fn construct<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
     fn block(&mut self, blk: &hir::Block, pred: CFGIndex) -> CFGIndex {
         if blk.targeted_by_break {
-            let expr_exit = self.add_ast_node(blk.id, &[]);
+            let expr_exit = self.add_ast_node(blk.hir_id.local_id, &[]);
 
             self.breakable_block_scopes.push(BlockScope {
-                block_expr_id: blk.id,
+                block_expr_id: blk.hir_id.local_id,
                 break_index: expr_exit,
             });
 
@@ -104,21 +104,22 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
 
             let expr_exit = self.opt_expr(&blk.expr, stmts_exit);
 
-            self.add_ast_node(blk.id, &[expr_exit])
+            self.add_ast_node(blk.hir_id.local_id, &[expr_exit])
         }
     }
 
     fn stmt(&mut self, stmt: &hir::Stmt, pred: CFGIndex) -> CFGIndex {
+        let hir_id = self.tcx.hir.node_to_hir_id(stmt.node.id());
         match stmt.node {
-            hir::StmtDecl(ref decl, id) => {
+            hir::StmtDecl(ref decl, _) => {
                 let exit = self.decl(&decl, pred);
-                self.add_ast_node(id, &[exit])
+                self.add_ast_node(hir_id.local_id, &[exit])
             }
 
-            hir::StmtExpr(ref expr, id) |
-            hir::StmtSemi(ref expr, id) => {
+            hir::StmtExpr(ref expr, _) |
+            hir::StmtSemi(ref expr, _) => {
                 let exit = self.expr(&expr, pred);
-                self.add_ast_node(id, &[exit])
+                self.add_ast_node(hir_id.local_id, &[exit])
             }
         }
     }
@@ -140,31 +141,31 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
             PatKind::Path(_) |
             PatKind::Lit(..) |
             PatKind::Range(..) |
-            PatKind::Wild => self.add_ast_node(pat.id, &[pred]),
+            PatKind::Wild => self.add_ast_node(pat.hir_id.local_id, &[pred]),
 
             PatKind::Box(ref subpat) |
             PatKind::Ref(ref subpat, _) |
             PatKind::Binding(.., Some(ref subpat)) => {
                 let subpat_exit = self.pat(&subpat, pred);
-                self.add_ast_node(pat.id, &[subpat_exit])
+                self.add_ast_node(pat.hir_id.local_id, &[subpat_exit])
             }
 
             PatKind::TupleStruct(_, ref subpats, _) |
             PatKind::Tuple(ref subpats, _) => {
                 let pats_exit = self.pats_all(subpats.iter(), pred);
-                self.add_ast_node(pat.id, &[pats_exit])
+                self.add_ast_node(pat.hir_id.local_id, &[pats_exit])
             }
 
             PatKind::Struct(_, ref subpats, _) => {
                 let pats_exit = self.pats_all(subpats.iter().map(|f| &f.node.pat), pred);
-                self.add_ast_node(pat.id, &[pats_exit])
+                self.add_ast_node(pat.hir_id.local_id, &[pats_exit])
             }
 
             PatKind::Slice(ref pre, ref vec, ref post) => {
                 let pre_exit = self.pats_all(pre.iter(), pred);
                 let vec_exit = self.pats_all(vec.iter(), pre_exit);
                 let post_exit = self.pats_all(post.iter(), vec_exit);
-                self.add_ast_node(pat.id, &[post_exit])
+                self.add_ast_node(pat.hir_id.local_id, &[post_exit])
             }
         }
     }
@@ -180,7 +181,7 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
         match expr.node {
             hir::ExprBlock(ref blk) => {
                 let blk_exit = self.block(&blk, pred);
-                self.add_ast_node(expr.id, &[blk_exit])
+                self.add_ast_node(expr.hir_id.local_id, &[blk_exit])
             }
 
             hir::ExprIf(ref cond, ref then, None) => {
@@ -200,7 +201,7 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
                 //
                 let cond_exit = self.expr(&cond, pred);                // 1
                 let then_exit = self.expr(&then, cond_exit);          // 2
-                self.add_ast_node(expr.id, &[cond_exit, then_exit])      // 3,4
+                self.add_ast_node(expr.hir_id.local_id, &[cond_exit, then_exit])      // 3,4
             }
 
             hir::ExprIf(ref cond, ref then, Some(ref otherwise)) => {
@@ -221,7 +222,7 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
                 let cond_exit = self.expr(&cond, pred);                // 1
                 let then_exit = self.expr(&then, cond_exit);          // 2
                 let else_exit = self.expr(&otherwise, cond_exit);      // 3
-                self.add_ast_node(expr.id, &[then_exit, else_exit])      // 4, 5
+                self.add_ast_node(expr.hir_id.local_id, &[then_exit, else_exit])      // 4, 5
             }
 
             hir::ExprWhile(ref cond, ref body, _) => {
@@ -245,12 +246,12 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
                 let loopback = self.add_dummy_node(&[pred]);              // 1
 
                 // Create expr_exit without pred (cond_exit)
-                let expr_exit = self.add_ast_node(expr.id, &[]);         // 3
+                let expr_exit = self.add_ast_node(expr.hir_id.local_id, &[]);         // 3
 
                 // The LoopScope needs to be on the loop_scopes stack while evaluating the
                 // condition and the body of the loop (both can break out of the loop)
                 self.loop_scopes.push(LoopScope {
-                    loop_id: expr.id,
+                    loop_id: expr.hir_id.local_id,
                     continue_index: loopback,
                     break_index: expr_exit
                 });
@@ -282,9 +283,9 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
                 // may cause additional edges.
 
                 let loopback = self.add_dummy_node(&[pred]);              // 1
-                let expr_exit = self.add_ast_node(expr.id, &[]);          // 2
+                let expr_exit = self.add_ast_node(expr.hir_id.local_id, &[]);          // 2
                 self.loop_scopes.push(LoopScope {
-                    loop_id: expr.id,
+                    loop_id: expr.hir_id.local_id,
                     continue_index: loopback,
                     break_index: expr_exit,
                 });
@@ -295,7 +296,7 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
             }
 
             hir::ExprMatch(ref discr, ref arms, _) => {
-                self.match_(expr.id, &discr, &arms, pred)
+                self.match_(expr.hir_id.local_id, &discr, &arms, pred)
             }
 
             hir::ExprBinary(op, ref l, ref r) if op.node.is_lazy() => {
@@ -315,30 +316,30 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
                 //
                 let l_exit = self.expr(&l, pred);                      // 1
                 let r_exit = self.expr(&r, l_exit);                    // 2
-                self.add_ast_node(expr.id, &[l_exit, r_exit])            // 3,4
+                self.add_ast_node(expr.hir_id.local_id, &[l_exit, r_exit])            // 3,4
             }
 
             hir::ExprRet(ref v) => {
                 let v_exit = self.opt_expr(v, pred);
-                let b = self.add_ast_node(expr.id, &[v_exit]);
+                let b = self.add_ast_node(expr.hir_id.local_id, &[v_exit]);
                 self.add_returning_edge(expr, b);
                 self.add_unreachable_node()
             }
 
             hir::ExprBreak(destination, ref opt_expr) => {
                 let v = self.opt_expr(opt_expr, pred);
-                let (scope_id, break_dest) =
+                let (target_scope, break_dest) =
                     self.find_scope_edge(expr, destination, ScopeCfKind::Break);
-                let b = self.add_ast_node(expr.id, &[v]);
-                self.add_exiting_edge(expr, b, scope_id, break_dest);
+                let b = self.add_ast_node(expr.hir_id.local_id, &[v]);
+                self.add_exiting_edge(expr, b, target_scope, break_dest);
                 self.add_unreachable_node()
             }
 
             hir::ExprAgain(destination) => {
-                let (scope_id, cont_dest) =
+                let (target_scope, cont_dest) =
                     self.find_scope_edge(expr, destination, ScopeCfKind::Continue);
-                let a = self.add_ast_node(expr.id, &[pred]);
-                self.add_exiting_edge(expr, a, scope_id, cont_dest);
+                let a = self.add_ast_node(expr.hir_id.local_id, &[pred]);
+                self.add_exiting_edge(expr, a, target_scope, cont_dest);
                 self.add_unreachable_node()
             }
 
@@ -389,6 +390,7 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
             hir::ExprUnary(_, ref e) |
             hir::ExprField(ref e, _) |
             hir::ExprTupField(ref e, _) |
+            hir::ExprYield(ref e) |
             hir::ExprRepeat(ref e, _) => {
                 self.straightline(expr, pred, Some(&**e).into_iter())
             }
@@ -396,7 +398,7 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
             hir::ExprInlineAsm(_, ref outputs, ref inputs) => {
                 let post_outputs = self.exprs(outputs.iter().map(|e| &*e), pred);
                 let post_inputs = self.exprs(inputs.iter().map(|e| &*e), post_outputs);
-                self.add_ast_node(expr.id, &[post_inputs])
+                self.add_ast_node(expr.hir_id.local_id, &[post_inputs])
             }
 
             hir::ExprClosure(..) |
@@ -443,10 +445,10 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
         //! Handles case of an expression that evaluates `subexprs` in order
 
         let subexprs_exit = self.exprs(subexprs, pred);
-        self.add_ast_node(expr.id, &[subexprs_exit])
+        self.add_ast_node(expr.hir_id.local_id, &[subexprs_exit])
     }
 
-    fn match_(&mut self, id: ast::NodeId, discr: &hir::Expr,
+    fn match_(&mut self, id: hir::ItemLocalId, discr: &hir::Expr,
               arms: &[hir::Arm], pred: CFGIndex) -> CFGIndex {
         // The CFG for match expression is quite complex, so no ASCII
         // art for it (yet).
@@ -551,8 +553,7 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
         self.add_node(CFGNodeData::Dummy, preds)
     }
 
-    fn add_ast_node(&mut self, id: ast::NodeId, preds: &[CFGIndex]) -> CFGIndex {
-        assert!(id != ast::DUMMY_NODE_ID);
+    fn add_ast_node(&mut self, id: hir::ItemLocalId, preds: &[CFGIndex]) -> CFGIndex {
         self.add_node(CFGNodeData::AST(id), preds)
     }
 
@@ -578,15 +579,14 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
     fn add_exiting_edge(&mut self,
                         from_expr: &hir::Expr,
                         from_index: CFGIndex,
-                        scope_id: ast::NodeId,
+                        target_scope: region::Scope,
                         to_index: CFGIndex) {
         let mut data = CFGEdgeData { exiting_scopes: vec![] };
-        let mut scope = CodeExtent::Misc(from_expr.id);
-        let target_scope = CodeExtent::Misc(scope_id);
-        let region_maps = self.tcx.region_maps(self.owner_def_id);
+        let mut scope = region::Scope::Node(from_expr.hir_id.local_id);
+        let region_scope_tree = self.tcx.region_scope_tree(self.owner_def_id);
         while scope != target_scope {
-            data.exiting_scopes.push(scope.node_id());
-            scope = region_maps.encl_scope(scope);
+            data.exiting_scopes.push(scope.item_local_id());
+            scope = region_scope_tree.encl_scope(scope);
         }
         self.graph.add_edge(from_index, to_index, data);
     }
@@ -606,13 +606,14 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
     fn find_scope_edge(&self,
                   expr: &hir::Expr,
                   destination: hir::Destination,
-                  scope_cf_kind: ScopeCfKind) -> (ast::NodeId, CFGIndex) {
+                  scope_cf_kind: ScopeCfKind) -> (region::Scope, CFGIndex) {
 
         match destination.target_id {
             hir::ScopeTarget::Block(block_expr_id) => {
                 for b in &self.breakable_block_scopes {
-                    if b.block_expr_id == block_expr_id {
-                        return (block_expr_id, match scope_cf_kind {
+                    if b.block_expr_id == self.tcx.hir.node_to_hir_id(block_expr_id).local_id {
+                        let scope_id = self.tcx.hir.node_to_hir_id(block_expr_id).local_id;
+                        return (region::Scope::Node(scope_id), match scope_cf_kind {
                             ScopeCfKind::Break => b.break_index,
                             ScopeCfKind::Continue => bug!("can't continue to block"),
                         });
@@ -622,8 +623,9 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
             }
             hir::ScopeTarget::Loop(hir::LoopIdResult::Ok(loop_id)) => {
                 for l in &self.loop_scopes {
-                    if l.loop_id == loop_id {
-                        return (loop_id, match scope_cf_kind {
+                    if l.loop_id == self.tcx.hir.node_to_hir_id(loop_id).local_id {
+                        let scope_id = self.tcx.hir.node_to_hir_id(loop_id).local_id;
+                        return (region::Scope::Node(scope_id), match scope_cf_kind {
                             ScopeCfKind::Break => l.break_index,
                             ScopeCfKind::Continue => l.continue_index,
                         });
diff --git a/src/librustc/cfg/graphviz.rs b/src/librustc/cfg/graphviz.rs
index 944b77dbf01fd..9241240caf043 100644
--- a/src/librustc/cfg/graphviz.rs
+++ b/src/librustc/cfg/graphviz.rs
@@ -15,40 +15,48 @@
 use graphviz as dot;
 use graphviz::IntoCow;
 
-use syntax::ast;
-
-use hir::map as hir_map;
 use cfg;
+use hir;
+use ty::TyCtxt;
 
 pub type Node<'a> = (cfg::CFGIndex, &'a cfg::CFGNode);
 pub type Edge<'a> = &'a cfg::CFGEdge;
 
-pub struct LabelledCFG<'a, 'hir: 'a> {
-    pub hir_map: &'a hir_map::Map<'hir>,
+pub struct LabelledCFG<'a, 'tcx: 'a> {
+    pub tcx: TyCtxt<'a, 'tcx, 'tcx>,
     pub cfg: &'a cfg::CFG,
     pub name: String,
     /// `labelled_edges` controls whether we emit labels on the edges
     pub labelled_edges: bool,
 }
 
-fn replace_newline_with_backslash_l(s: String) -> String {
-    // Replacing newlines with \\l causes each line to be left-aligned,
-    // improving presentation of (long) pretty-printed expressions.
-    if s.contains("\n") {
-        let mut s = s.replace("\n", "\\l");
-        // Apparently left-alignment applies to the line that precedes
-        // \l, not the line that follows; so, add \l at end of string
-        // if not already present, ensuring last line gets left-aligned
-        // as well.
-        let mut last_two: Vec<_> =
-            s.chars().rev().take(2).collect();
-        last_two.reverse();
-        if last_two != ['\\', 'l'] {
-            s.push_str("\\l");
+impl<'a, 'tcx> LabelledCFG<'a, 'tcx> {
+    fn local_id_to_string(&self, local_id: hir::ItemLocalId) -> String {
+        assert!(self.cfg.owner_def_id.is_local());
+        let node_id = self.tcx.hir.hir_to_node_id(hir::HirId {
+            owner: self.tcx.hir.def_index_to_hir_id(self.cfg.owner_def_id.index).owner,
+            local_id
+        });
+        let s = self.tcx.hir.node_to_string(node_id);
+
+        // Replacing newlines with \\l causes each line to be left-aligned,
+        // improving presentation of (long) pretty-printed expressions.
+        if s.contains("\n") {
+            let mut s = s.replace("\n", "\\l");
+            // Apparently left-alignment applies to the line that precedes
+            // \l, not the line that follows; so, add \l at end of string
+            // if not already present, ensuring last line gets left-aligned
+            // as well.
+            let mut last_two: Vec<_> =
+                s.chars().rev().take(2).collect();
+            last_two.reverse();
+            if last_two != ['\\', 'l'] {
+                s.push_str("\\l");
+            }
+            s
+        } else {
+            s
         }
-        s
-    } else {
-        s
     }
 }
 
@@ -66,12 +74,10 @@ impl<'a, 'hir> dot::Labeller<'a> for LabelledCFG<'a, 'hir> {
             dot::LabelText::LabelStr("entry".into_cow())
         } else if i == self.cfg.exit {
             dot::LabelText::LabelStr("exit".into_cow())
-        } else if n.data.id() == ast::DUMMY_NODE_ID {
+        } else if n.data.id() == hir::DUMMY_ITEM_LOCAL_ID {
             dot::LabelText::LabelStr("(dummy_node)".into_cow())
         } else {
-            let s = self.hir_map.node_to_string(n.data.id());
-            // left-aligns the lines
-            let s = replace_newline_with_backslash_l(s);
+            let s = self.local_id_to_string(n.data.id());
             dot::LabelText::EscStr(s.into_cow())
         }
     }
@@ -82,15 +88,13 @@ impl<'a, 'hir> dot::Labeller<'a> for LabelledCFG<'a, 'hir> {
             return dot::LabelText::EscStr(label.into_cow());
         }
         let mut put_one = false;
-        for (i, &node_id) in e.data.exiting_scopes.iter().enumerate() {
+        for (i, &id) in e.data.exiting_scopes.iter().enumerate() {
             if put_one {
                 label.push_str(",\\l");
             } else {
                 put_one = true;
             }
-            let s = self.hir_map.node_to_string(node_id);
-            // left-aligns the lines
-            let s = replace_newline_with_backslash_l(s);
+            let s = self.local_id_to_string(id);
             label.push_str(&format!("exiting scope_{} {}",
                                    i,
                                    &s[..]));
diff --git a/src/librustc/cfg/mod.rs b/src/librustc/cfg/mod.rs
index 1473dbb1676f3..b379d3956e944 100644
--- a/src/librustc/cfg/mod.rs
+++ b/src/librustc/cfg/mod.rs
@@ -13,13 +13,14 @@
 
 use rustc_data_structures::graph;
 use ty::TyCtxt;
-use syntax::ast;
 use hir;
+use hir::def_id::DefId;
 
 mod construct;
 pub mod graphviz;
 
 pub struct CFG {
+    pub owner_def_id: DefId,
     pub graph: CFGGraph,
     pub entry: CFGIndex,
     pub exit: CFGIndex,
@@ -27,7 +28,7 @@ pub struct CFG {
 
 #[derive(Copy, Clone, Debug, PartialEq)]
 pub enum CFGNodeData {
-    AST(ast::NodeId),
+    AST(hir::ItemLocalId),
     Entry,
     Exit,
     Dummy,
@@ -35,18 +36,18 @@ pub enum CFGNodeData {
 }
 
 impl CFGNodeData {
-    pub fn id(&self) -> ast::NodeId {
+    pub fn id(&self) -> hir::ItemLocalId {
         if let CFGNodeData::AST(id) = *self {
             id
         } else {
-            ast::DUMMY_NODE_ID
+            hir::DUMMY_ITEM_LOCAL_ID
         }
     }
 }
 
 #[derive(Debug)]
 pub struct CFGEdgeData {
-    pub exiting_scopes: Vec<ast::NodeId>
+    pub exiting_scopes: Vec<hir::ItemLocalId>
 }
 
 pub type CFGIndex = graph::NodeIndex;
@@ -63,7 +64,7 @@ impl CFG {
         construct::construct(tcx, body)
     }
 
-    pub fn node_is_reachable(&self, id: ast::NodeId) -> bool {
+    pub fn node_is_reachable(&self, id: hir::ItemLocalId) -> bool {
         self.graph.depth_traverse(self.entry, graph::OUTGOING)
                   .any(|idx| self.graph.node_data(idx).id() == id)
     }
diff --git a/src/librustc/dep_graph/dep_node.rs b/src/librustc/dep_graph/dep_node.rs
index 01fff60528394..c438944cf0131 100644
--- a/src/librustc/dep_graph/dep_node.rs
+++ b/src/librustc/dep_graph/dep_node.rs
@@ -62,6 +62,7 @@
 
 use hir::def_id::{CrateNum, DefId};
 use hir::map::DefPathHash;
+use hir::HirId;
 
 use ich::Fingerprint;
 use ty::{TyCtxt, Instance, InstanceDef};
@@ -394,7 +395,7 @@ define_dep_nodes!( <'tcx>
     [] WorkProduct(WorkProductId),
 
     // Represents different phases in the compiler.
-    [] RegionMaps(DefId),
+    [] RegionScopeTree(DefId),
     [] Coherence,
     [] CoherenceInherentImplOverlapCheck,
     [] Resolve,
@@ -434,6 +435,7 @@ define_dep_nodes!( <'tcx>
     [] ImplPolarity(DefId),
     [] ClosureKind(DefId),
     [] FnSignature(DefId),
+    [] GenSignature(DefId),
     [] CoerceUnsizedInfo(DefId),
 
     [] ItemVarianceConstraints(DefId),
@@ -526,6 +528,9 @@ define_dep_nodes!( <'tcx>
     [] HasGlobalAllocator(DefId),
     [] ExternCrate(DefId),
     [] LintLevels,
+    [] Specializes { impl1: DefId, impl2: DefId },
+    [] InScopeTraits(HirId),
+    [] ModuleExports(HirId),
 );
 
 trait DepNodeParams<'a, 'gcx: 'tcx + 'a, 'tcx: 'a> : fmt::Debug {
diff --git a/src/librustc/diagnostics.rs b/src/librustc/diagnostics.rs
index 412759e11423e..be7bb4d811413 100644
--- a/src/librustc/diagnostics.rs
+++ b/src/librustc/diagnostics.rs
@@ -688,8 +688,8 @@ See also https://doc.rust-lang.org/book/first-edition/no-stdlib.html
 "##,
 
 E0214: r##"
-A generic type was described using parentheses rather than angle brackets. For
-example:
+A generic type was described using parentheses rather than angle brackets.
+For example:
 
 ```compile_fail,E0214
 fn main() {
@@ -702,6 +702,93 @@ Parentheses are currently only used with generic types when defining parameters
 for `Fn`-family traits.
 "##,
 
+E0230: r##"
+The `#[rustc_on_unimplemented]` attribute lets you specify a custom error
+message for when a particular trait isn't implemented on a type placed in a
+position that needs that trait. For example, when the following code is
+compiled:
+
+```compile_fail
+#![feature(on_unimplemented)]
+
+fn foo<T: Index<u8>>(x: T){}
+
+#[rustc_on_unimplemented = "the type `{Self}` cannot be indexed by `{Idx}`"]
+trait Index<Idx> { /* ... */ }
+
+foo(true); // `bool` does not implement `Index<u8>`
+```
+
+There will be an error about `bool` not implementing `Index<u8>`, followed by a
+note saying "the type `bool` cannot be indexed by `u8`".
+
+As you can see, you can specify type parameters in curly braces for
+substitution with the actual types (using the regular format string syntax) in
+a given situation. Furthermore, `{Self}` will substitute to the type (in this
+case, `bool`) that we tried to use.
+
+This error appears when the curly braces contain an identifier which doesn't
+match with any of the type parameters or the string `Self`. This might happen
+if you misspelled a type parameter, or if you intended to use literal curly
+braces. If it is the latter, escape the curly braces with a second curly brace
+of the same type; e.g. a literal `{` is `{{`.
+"##,
+
+E0231: r##"
+The `#[rustc_on_unimplemented]` attribute lets you specify a custom error
+message for when a particular trait isn't implemented on a type placed in a
+position that needs that trait. For example, when the following code is
+compiled:
+
+```compile_fail
+#![feature(on_unimplemented)]
+
+fn foo<T: Index<u8>>(x: T){}
+
+#[rustc_on_unimplemented = "the type `{Self}` cannot be indexed by `{Idx}`"]
+trait Index<Idx> { /* ... */ }
+
+foo(true); // `bool` does not implement `Index<u8>`
+```
+
+there will be an error about `bool` not implementing `Index<u8>`, followed by a
+note saying "the type `bool` cannot be indexed by `u8`".
+
+As you can see, you can specify type parameters in curly braces for
+substitution with the actual types (using the regular format string syntax) in
+a given situation. Furthermore, `{Self}` will substitute to the type (in this
+case, `bool`) that we tried to use.
+
+This error appears when the curly braces do not contain an identifier. Please
+add one of the same name as a type parameter. If you intended to use literal
+braces, use `{{` and `}}` to escape them.
+"##,
+
+E0232: r##"
+The `#[rustc_on_unimplemented]` attribute lets you specify a custom error
+message for when a particular trait isn't implemented on a type placed in a
+position that needs that trait. For example, when the following code is
+compiled:
+
+```compile_fail
+#![feature(on_unimplemented)]
+
+fn foo<T: Index<u8>>(x: T){}
+
+#[rustc_on_unimplemented = "the type `{Self}` cannot be indexed by `{Idx}`"]
+trait Index<Idx> { /* ... */ }
+
+foo(true); // `bool` does not implement `Index<u8>`
+```
+
+there will be an error about `bool` not implementing `Index<u8>`, followed by a
+note saying "the type `bool` cannot be indexed by `u8`".
+
+For this to work, some note must be specified. An empty attribute will not do
+anything, please remove the attribute or add some helpful note for users of the
+trait.
+"##,
+
 E0261: r##"
 When using a lifetime like `'a` in a type, it must be declared before being
 used.
@@ -917,92 +1004,6 @@ for v in &vs {
 ```
 "##,
 
-E0272: r##"
-The `#[rustc_on_unimplemented]` attribute lets you specify a custom error
-message for when a particular trait isn't implemented on a type placed in a
-position that needs that trait. For example, when the following code is
-compiled:
-
-```compile_fail
-#![feature(on_unimplemented)]
-
-fn foo<T: Index<u8>>(x: T){}
-
-#[rustc_on_unimplemented = "the type `{Self}` cannot be indexed by `{Idx}`"]
-trait Index<Idx> { /* ... */ }
-
-foo(true); // `bool` does not implement `Index<u8>`
-```
-
-There will be an error about `bool` not implementing `Index<u8>`, followed by a
-note saying "the type `bool` cannot be indexed by `u8`".
-
-As you can see, you can specify type parameters in curly braces for
-substitution with the actual types (using the regular format string syntax) in
-a given situation. Furthermore, `{Self}` will substitute to the type (in this
-case, `bool`) that we tried to use.
-
-This error appears when the curly braces contain an identifier which doesn't
-match with any of the type parameters or the string `Self`. This might happen
-if you misspelled a type parameter, or if you intended to use literal curly
-braces. If it is the latter, escape the curly braces with a second curly brace
-of the same type; e.g. a literal `{` is `{{`.
-"##,
-
-E0273: r##"
-The `#[rustc_on_unimplemented]` attribute lets you specify a custom error
-message for when a particular trait isn't implemented on a type placed in a
-position that needs that trait. For example, when the following code is
-compiled:
-
-```compile_fail
-#![feature(on_unimplemented)]
-
-fn foo<T: Index<u8>>(x: T){}
-
-#[rustc_on_unimplemented = "the type `{Self}` cannot be indexed by `{Idx}`"]
-trait Index<Idx> { /* ... */ }
-
-foo(true); // `bool` does not implement `Index<u8>`
-```
-
-there will be an error about `bool` not implementing `Index<u8>`, followed by a
-note saying "the type `bool` cannot be indexed by `u8`".
-
-As you can see, you can specify type parameters in curly braces for
-substitution with the actual types (using the regular format string syntax) in
-a given situation. Furthermore, `{Self}` will substitute to the type (in this
-case, `bool`) that we tried to use.
-
-This error appears when the curly braces do not contain an identifier. Please
-add one of the same name as a type parameter. If you intended to use literal
-braces, use `{{` and `}}` to escape them.
-"##,
-
-E0274: r##"
-The `#[rustc_on_unimplemented]` attribute lets you specify a custom error
-message for when a particular trait isn't implemented on a type placed in a
-position that needs that trait. For example, when the following code is
-compiled:
-
-```compile_fail
-#![feature(on_unimplemented)]
-
-fn foo<T: Index<u8>>(x: T){}
-
-#[rustc_on_unimplemented = "the type `{Self}` cannot be indexed by `{Idx}`"]
-trait Index<Idx> { /* ... */ }
-
-foo(true); // `bool` does not implement `Index<u8>`
-```
-
-there will be an error about `bool` not implementing `Index<u8>`, followed by a
-note saying "the type `bool` cannot be indexed by `u8`".
-
-For this to work, some note must be specified. An empty attribute will not do
-anything, please remove the attribute or add some helpful note for users of the
-trait.
-"##,
 
 E0275: r##"
 This error occurs when there was a recursive trait requirement that overflowed
@@ -2011,6 +2012,9 @@ register_diagnostics! {
 //  E0102, // replaced with E0282
 //  E0134,
 //  E0135,
+//  E0272, // on_unimplemented #0
+//  E0273, // on_unimplemented #1
+//  E0274, // on_unimplemented #2
     E0278, // requirement is not satisfied
     E0279, // requirement is not satisfied
     E0280, // requirement is not satisfied
@@ -2045,4 +2049,5 @@ register_diagnostics! {
     E0495, // cannot infer an appropriate lifetime due to conflicting requirements
     E0566, // conflicting representation hints
     E0623, // lifetime mismatch where both parameters are anonymous regions
+    E0628, // generators cannot have explicit arguments
 }
diff --git a/src/librustc/hir/intravisit.rs b/src/librustc/hir/intravisit.rs
index d52cc26eaebc6..880605ee377f7 100644
--- a/src/librustc/hir/intravisit.rs
+++ b/src/librustc/hir/intravisit.rs
@@ -979,7 +979,7 @@ pub fn walk_expr<'v, V: Visitor<'v>>(visitor: &mut V, expression: &'v Expr) {
             visitor.visit_expr(subexpression);
             walk_list!(visitor, visit_arm, arms);
         }
-        ExprClosure(_, ref function_declaration, body, _fn_decl_span) => {
+        ExprClosure(_, ref function_declaration, body, _fn_decl_span, _gen) => {
             visitor.visit_fn(FnKind::Closure(&expression.attrs),
                              function_declaration,
                              body,
@@ -1043,6 +1043,9 @@ pub fn walk_expr<'v, V: Visitor<'v>>(visitor: &mut V, expression: &'v Expr) {
                 visitor.visit_expr(input)
             }
         }
+        ExprYield(ref subexpression) => {
+            visitor.visit_expr(subexpression);
+        }
     }
 }
 
diff --git a/src/librustc/hir/lowering.rs b/src/librustc/hir/lowering.rs
index ac26cbc833dea..0f69c06c417a1 100644
--- a/src/librustc/hir/lowering.rs
+++ b/src/librustc/hir/lowering.rs
@@ -93,6 +93,8 @@ pub struct LoweringContext<'a> {
     trait_impls: BTreeMap<DefId, Vec<NodeId>>,
     trait_default_impl: BTreeMap<DefId, NodeId>,
 
+    is_generator: bool,
+
     catch_scopes: Vec<NodeId>,
     loop_scopes: Vec<NodeId>,
     is_in_loop_condition: bool,
@@ -145,6 +147,7 @@ pub fn lower_crate(sess: &Session,
         current_hir_id_owner: vec![(CRATE_DEF_INDEX, 0)],
         item_local_id_counters: NodeMap(),
         node_id_to_hir_id: IndexVec::new(),
+        is_generator: false,
     }.lower_crate(krate)
 }
 
@@ -393,6 +396,7 @@ impl<'a> LoweringContext<'a> {
             arguments: decl.map_or(hir_vec![], |decl| {
                 decl.inputs.iter().map(|x| self.lower_arg(x)).collect()
             }),
+            is_generator: self.is_generator,
             value,
         };
         let id = body.id();
@@ -421,8 +425,7 @@ impl<'a> LoweringContext<'a> {
         Symbol::gensym(s)
     }
 
-    fn allow_internal_unstable(&self, reason: CompilerDesugaringKind, mut span: Span)
-        -> Span
+    fn allow_internal_unstable(&self, reason: CompilerDesugaringKind, span: Span) -> Span
     {
         let mark = Mark::fresh(Mark::root());
         mark.set_expn_info(codemap::ExpnInfo {
@@ -434,8 +437,7 @@ impl<'a> LoweringContext<'a> {
                 allow_internal_unsafe: false,
             },
         });
-        span.ctxt = SyntaxContext::empty().apply_mark(mark);
-        span
+        span.with_ctxt(SyntaxContext::empty().apply_mark(mark))
     }
 
     fn with_catch_scope<T, F>(&mut self, catch_id: NodeId, f: F) -> T
@@ -453,6 +455,16 @@ impl<'a> LoweringContext<'a> {
         result
     }
 
+    fn lower_body<F>(&mut self, decl: Option<&FnDecl>, f: F) -> hir::BodyId
+        where F: FnOnce(&mut LoweringContext) -> hir::Expr
+    {
+        let prev = mem::replace(&mut self.is_generator, false);
+        let result = f(self);
+        let r = self.record_body(result, decl);
+        self.is_generator = prev;
+        return r
+    }
+
     fn with_loop_scope<T, F>(&mut self, loop_id: NodeId, f: F) -> T
         where F: FnOnce(&mut LoweringContext) -> T
     {
@@ -599,7 +611,7 @@ impl<'a> LoweringContext<'a> {
             TyKind::Slice(ref ty) => hir::TySlice(self.lower_ty(ty)),
             TyKind::Ptr(ref mt) => hir::TyPtr(self.lower_mt(mt)),
             TyKind::Rptr(ref region, ref mt) => {
-                let span = Span { hi: t.span.lo, ..t.span };
+                let span = t.span.with_hi(t.span.lo());
                 let lifetime = match *region {
                     Some(ref lt) => self.lower_lifetime(lt),
                     None => self.elided_lifetime(span)
@@ -637,13 +649,12 @@ impl<'a> LoweringContext<'a> {
                 })))
             }
             TyKind::Array(ref ty, ref length) => {
-                let length = self.lower_expr(length);
-                hir::TyArray(self.lower_ty(ty),
-                             self.record_body(length, None))
+                let length = self.lower_body(None, |this| this.lower_expr(length));
+                hir::TyArray(self.lower_ty(ty), length)
             }
             TyKind::Typeof(ref expr) => {
-                let expr = self.lower_expr(expr);
-                hir::TyTypeof(self.record_body(expr, None))
+                let expr = self.lower_body(None, |this| this.lower_expr(expr));
+                hir::TyTypeof(expr)
             }
             TyKind::TraitObject(ref bounds) => {
                 let mut lifetime_bound = None;
@@ -700,8 +711,7 @@ impl<'a> LoweringContext<'a> {
                 attrs: self.lower_attrs(&v.node.attrs),
                 data: self.lower_variant_data(&v.node.data),
                 disr_expr: v.node.disr_expr.as_ref().map(|e| {
-                    let e = self.lower_expr(e);
-                    self.record_body(e, None)
+                    self.lower_body(None, |this| this.lower_expr(e))
                 }),
             },
             span: v.span,
@@ -1225,7 +1235,7 @@ impl<'a> LoweringContext<'a> {
             name: self.lower_ident(match f.ident {
                 Some(ident) => ident,
                 // FIXME(jseyfried) positional field hygiene
-                None => Ident { name: Symbol::intern(&index.to_string()), ctxt: f.span.ctxt },
+                None => Ident { name: Symbol::intern(&index.to_string()), ctxt: f.span.ctxt() },
             }),
             vis: self.lower_visibility(&f.vis, None),
             ty: self.lower_ty(&f.ty),
@@ -1368,21 +1378,21 @@ impl<'a> LoweringContext<'a> {
                 hir::ItemUse(path, kind)
             }
             ItemKind::Static(ref t, m, ref e) => {
-                let value = self.lower_expr(e);
+                let value = self.lower_body(None, |this| this.lower_expr(e));
                 hir::ItemStatic(self.lower_ty(t),
                                 self.lower_mutability(m),
-                                self.record_body(value, None))
+                                value)
             }
             ItemKind::Const(ref t, ref e) => {
-                let value = self.lower_expr(e);
-                hir::ItemConst(self.lower_ty(t),
-                               self.record_body(value, None))
+                let value = self.lower_body(None, |this| this.lower_expr(e));
+                hir::ItemConst(self.lower_ty(t), value)
             }
             ItemKind::Fn(ref decl, unsafety, constness, abi, ref generics, ref body) => {
                 self.with_new_scopes(|this| {
-                    let body = this.lower_block(body, false);
-                    let body = this.expr_block(body, ThinVec::new());
-                    let body_id = this.record_body(body, Some(decl));
+                    let body_id = this.lower_body(Some(decl), |this| {
+                        let body = this.lower_block(body, false);
+                        this.expr_block(body, ThinVec::new())
+                    });
                     hir::ItemFn(this.lower_fn_decl(decl),
                                               this.lower_unsafety(unsafety),
                                               this.lower_constness(constness),
@@ -1478,8 +1488,7 @@ impl<'a> LoweringContext<'a> {
                     TraitItemKind::Const(ref ty, ref default) => {
                         hir::TraitItemKind::Const(this.lower_ty(ty),
                                                   default.as_ref().map(|x| {
-                            let value = this.lower_expr(x);
-                            this.record_body(value, None)
+                            this.lower_body(None, |this| this.lower_expr(x))
                         }))
                     }
                     TraitItemKind::Method(ref sig, None) => {
@@ -1488,9 +1497,10 @@ impl<'a> LoweringContext<'a> {
                                                    hir::TraitMethod::Required(names))
                     }
                     TraitItemKind::Method(ref sig, Some(ref body)) => {
-                        let body = this.lower_block(body, false);
-                        let expr = this.expr_block(body, ThinVec::new());
-                        let body_id = this.record_body(expr, Some(&sig.decl));
+                        let body_id = this.lower_body(Some(&sig.decl), |this| {
+                            let body = this.lower_block(body, false);
+                            this.expr_block(body, ThinVec::new())
+                        });
                         hir::TraitItemKind::Method(this.lower_method_sig(sig),
                                                    hir::TraitMethod::Provided(body_id))
                     }
@@ -1542,14 +1552,14 @@ impl<'a> LoweringContext<'a> {
                 defaultness: this.lower_defaultness(i.defaultness, true /* [1] */),
                 node: match i.node {
                     ImplItemKind::Const(ref ty, ref expr) => {
-                        let value = this.lower_expr(expr);
-                        let body_id = this.record_body(value, None);
+                        let body_id = this.lower_body(None, |this| this.lower_expr(expr));
                         hir::ImplItemKind::Const(this.lower_ty(ty), body_id)
                     }
                     ImplItemKind::Method(ref sig, ref body) => {
-                        let body = this.lower_block(body, false);
-                        let expr = this.expr_block(body, ThinVec::new());
-                        let body_id = this.record_body(expr, Some(&sig.decl));
+                        let body_id = this.lower_body(Some(&sig.decl), |this| {
+                            let body = this.lower_block(body, false);
+                            this.expr_block(body, ThinVec::new())
+                        });
                         hir::ImplItemKind::Method(this.lower_method_sig(sig), body_id)
                     }
                     ImplItemKind::Type(ref ty) => hir::ImplItemKind::Type(this.lower_ty(ty)),
@@ -1928,8 +1938,8 @@ impl<'a> LoweringContext<'a> {
             }
             ExprKind::Repeat(ref expr, ref count) => {
                 let expr = P(self.lower_expr(expr));
-                let count = self.lower_expr(count);
-                hir::ExprRepeat(expr, self.record_body(count, None))
+                let count = self.lower_body(None, |this| this.lower_expr(count));
+                hir::ExprRepeat(expr, count)
             }
             ExprKind::Tup(ref elts) => {
                 hir::ExprTup(elts.iter().map(|x| self.lower_expr(x)).collect())
@@ -2027,11 +2037,22 @@ impl<'a> LoweringContext<'a> {
             ExprKind::Closure(capture_clause, ref decl, ref body, fn_decl_span) => {
                 self.with_new_scopes(|this| {
                     this.with_parent_def(e.id, |this| {
-                        let expr = this.lower_expr(body);
+                        let mut is_generator = false;
+                        let body_id = this.lower_body(Some(decl), |this| {
+                            let e = this.lower_expr(body);
+                            is_generator = this.is_generator;
+                            e
+                        });
+                        if is_generator && !decl.inputs.is_empty() {
+                            span_err!(this.sess, fn_decl_span, E0628,
+                                      "generators cannot have explicit arguments");
+                            this.sess.abort_if_errors();
+                        }
                         hir::ExprClosure(this.lower_capture_clause(capture_clause),
                                          this.lower_fn_decl(decl),
-                                         this.record_body(expr, Some(decl)),
-                                         fn_decl_span)
+                                         body_id,
+                                         fn_decl_span,
+                                         is_generator)
                     })
                 })
             }
@@ -2172,6 +2193,14 @@ impl<'a> LoweringContext<'a> {
                 return ex;
             }
 
+            ExprKind::Yield(ref opt_expr) => {
+                self.is_generator = true;
+                let expr = opt_expr.as_ref().map(|x| self.lower_expr(x)).unwrap_or_else(|| {
+                    self.expr(e.span, hir::ExprTup(hir_vec![]), ThinVec::new())
+                });
+                hir::ExprYield(P(expr))
+            }
+
             // Desugar ExprIfLet
             // From: `if let <pat> = <sub_expr> <body> [<else_opt>]`
             ExprKind::IfLet(ref pat, ref sub_expr, ref body, ref else_opt) => {
diff --git a/src/librustc/hir/map/blocks.rs b/src/librustc/hir/map/blocks.rs
index 1b7eb1585671e..d2888dcf6aaa4 100644
--- a/src/librustc/hir/map/blocks.rs
+++ b/src/librustc/hir/map/blocks.rs
@@ -264,7 +264,7 @@ impl<'a> FnLikeNode<'a> {
                 }
             },
             map::NodeExpr(e) => match e.node {
-                ast::ExprClosure(_, ref decl, block, _fn_decl_span) =>
+                ast::ExprClosure(_, ref decl, block, _fn_decl_span, _gen) =>
                     closure(ClosureParts::new(&decl, block, e.id, e.span, &e.attrs)),
                 _ => bug!("expr FnLikeNode that is not fn-like"),
             },
diff --git a/src/librustc/hir/map/mod.rs b/src/librustc/hir/map/mod.rs
index 63a5b70cb81a9..e54df2d50d8eb 100644
--- a/src/librustc/hir/map/mod.rs
+++ b/src/librustc/hir/map/mod.rs
@@ -26,7 +26,7 @@ use syntax_pos::Span;
 
 use hir::*;
 use hir::print::Nested;
-use util::nodemap::DefIdMap;
+use util::nodemap::{DefIdMap, FxHashMap};
 
 use arena::TypedArena;
 use std::cell::RefCell;
@@ -151,7 +151,9 @@ impl<'hir> MapEntry<'hir> {
             EntryTyParam(_, _, n) => NodeTyParam(n),
             EntryVisibility(_, _, n) => NodeVisibility(n),
             EntryLocal(_, _, n) => NodeLocal(n),
-            _ => return None
+
+            NotPresent |
+            RootCrate(_) => return None
         })
     }
 
@@ -184,7 +186,7 @@ impl<'hir> MapEntry<'hir> {
 
             EntryExpr(_, _, expr) => {
                 match expr.node {
-                    ExprClosure(.., body, _) => Some(body),
+                    ExprClosure(.., body, _, _) => Some(body),
                     _ => None,
                 }
             }
@@ -249,6 +251,9 @@ pub struct Map<'hir> {
 
     /// Bodies inlined from other crates are cached here.
     inlined_bodies: RefCell<DefIdMap<&'hir Body>>,
+
+    /// The reverse mapping of `node_to_hir_id`.
+    hir_to_node_id: FxHashMap<HirId, NodeId>,
 }
 
 impl<'hir> Map<'hir> {
@@ -337,6 +342,11 @@ impl<'hir> Map<'hir> {
         self.definitions.as_local_node_id(def_id)
     }
 
+    #[inline]
+    pub fn hir_to_node_id(&self, hir_id: HirId) -> NodeId {
+        self.hir_to_node_id[&hir_id]
+    }
+
     #[inline]
     pub fn node_to_hir_id(&self, node_id: NodeId) -> HirId {
         self.definitions.node_to_hir_id(node_id)
@@ -1019,10 +1029,15 @@ pub fn map_crate<'hir>(forest: &'hir mut Forest,
               entries, vector_length, (entries as f64 / vector_length as f64) * 100.);
     }
 
+    // Build the reverse mapping of `node_to_hir_id`.
+    let hir_to_node_id = definitions.node_to_hir_id.iter_enumerated()
+        .map(|(node_id, &hir_id)| (hir_id, node_id)).collect();
+
     let map = Map {
         forest,
         dep_graph: forest.dep_graph.clone(),
         map,
+        hir_to_node_id,
         definitions,
         inlined_bodies: RefCell::new(DefIdMap()),
     };
diff --git a/src/librustc/hir/mod.rs b/src/librustc/hir/mod.rs
index df67f8416212c..46b8cb0a2e2c8 100644
--- a/src/librustc/hir/mod.rs
+++ b/src/librustc/hir/mod.rs
@@ -929,7 +929,8 @@ pub struct BodyId {
 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 pub struct Body {
     pub arguments: HirVec<Arg>,
-    pub value: Expr
+    pub value: Expr,
+    pub is_generator: bool,
 }
 
 impl Body {
@@ -1007,7 +1008,10 @@ pub enum Expr_ {
     /// A closure (for example, `move |a, b, c| {a + b + c}`).
     ///
     /// The final span is the span of the argument block `|...|`
-    ExprClosure(CaptureClause, P<FnDecl>, BodyId, Span),
+    ///
+    /// This may also be a generator literal, indicated by the final boolean,
+    /// in that case there is an GeneratorClause.
+    ExprClosure(CaptureClause, P<FnDecl>, BodyId, Span, bool),
     /// A block (`{ ... }`)
     ExprBlock(P<Block>),
 
@@ -1052,6 +1056,9 @@ pub enum Expr_ {
     /// For example, `[1; 5]`. The first expression is the element
     /// to be repeated; the second is the number of times to repeat it.
     ExprRepeat(P<Expr>, BodyId),
+
+    /// A suspension point for generators. This is `yield <expr>` in Rust.
+    ExprYield(P<Expr>),
 }
 
 /// Optionally `Self`-qualified value/type path or associated extension.
diff --git a/src/librustc/hir/print.rs b/src/librustc/hir/print.rs
index 876875bce4a5e..dce824bd513a7 100644
--- a/src/librustc/hir/print.rs
+++ b/src/librustc/hir/print.rs
@@ -262,7 +262,7 @@ impl<'a> State<'a> {
                              indented: usize,
                              close_box: bool)
                              -> io::Result<()> {
-        self.maybe_print_comment(span.hi)?;
+        self.maybe_print_comment(span.hi())?;
         self.break_offset_if_not_bol(1, -(indented as isize))?;
         self.s.word("}")?;
         if close_box {
@@ -324,12 +324,12 @@ impl<'a> State<'a> {
         let len = elts.len();
         let mut i = 0;
         for elt in elts {
-            self.maybe_print_comment(get_span(elt).hi)?;
+            self.maybe_print_comment(get_span(elt).hi())?;
             op(self, elt)?;
             i += 1;
             if i < len {
                 self.s.word(",")?;
-                self.maybe_print_trailing_comment(get_span(elt), Some(get_span(&elts[i]).hi))?;
+                self.maybe_print_trailing_comment(get_span(elt), Some(get_span(&elts[i]).hi()))?;
                 self.space_if_not_bol()?;
             }
         }
@@ -368,7 +368,7 @@ impl<'a> State<'a> {
     }
 
     pub fn print_type(&mut self, ty: &hir::Ty) -> io::Result<()> {
-        self.maybe_print_comment(ty.span.lo)?;
+        self.maybe_print_comment(ty.span.lo())?;
         self.ibox(0)?;
         match ty.node {
             hir::TySlice(ref ty) => {
@@ -458,7 +458,7 @@ impl<'a> State<'a> {
 
     pub fn print_foreign_item(&mut self, item: &hir::ForeignItem) -> io::Result<()> {
         self.hardbreak_if_not_bol()?;
-        self.maybe_print_comment(item.span.lo)?;
+        self.maybe_print_comment(item.span.lo())?;
         self.print_outer_attributes(&item.attrs)?;
         match item.node {
             hir::ForeignItemFn(ref decl, ref arg_names, ref generics) => {
@@ -531,7 +531,7 @@ impl<'a> State<'a> {
     /// Pretty-print an item
     pub fn print_item(&mut self, item: &hir::Item) -> io::Result<()> {
         self.hardbreak_if_not_bol()?;
-        self.maybe_print_comment(item.span.lo)?;
+        self.maybe_print_comment(item.span.lo())?;
         self.print_outer_attributes(&item.attrs)?;
         self.ann.pre(self, NodeItem(item))?;
         match item.node {
@@ -797,7 +797,7 @@ impl<'a> State<'a> {
         self.bopen()?;
         for v in variants {
             self.space_if_not_bol()?;
-            self.maybe_print_comment(v.span.lo)?;
+            self.maybe_print_comment(v.span.lo())?;
             self.print_outer_attributes(&v.node.attrs)?;
             self.ibox(indent_unit)?;
             self.print_variant(v)?;
@@ -842,7 +842,7 @@ impl<'a> State<'a> {
             if struct_def.is_tuple() {
                 self.popen()?;
                 self.commasep(Inconsistent, struct_def.fields(), |s, field| {
-                    s.maybe_print_comment(field.span.lo)?;
+                    s.maybe_print_comment(field.span.lo())?;
                     s.print_outer_attributes(&field.attrs)?;
                     s.print_visibility(&field.vis)?;
                     s.print_type(&field.ty)
@@ -863,7 +863,7 @@ impl<'a> State<'a> {
 
             for field in struct_def.fields() {
                 self.hardbreak_if_not_bol()?;
-                self.maybe_print_comment(field.span.lo)?;
+                self.maybe_print_comment(field.span.lo())?;
                 self.print_outer_attributes(&field.attrs)?;
                 self.print_visibility(&field.vis)?;
                 self.print_name(field.name)?;
@@ -908,7 +908,7 @@ impl<'a> State<'a> {
     pub fn print_trait_item(&mut self, ti: &hir::TraitItem) -> io::Result<()> {
         self.ann.pre(self, NodeSubItem(ti.id))?;
         self.hardbreak_if_not_bol()?;
-        self.maybe_print_comment(ti.span.lo)?;
+        self.maybe_print_comment(ti.span.lo())?;
         self.print_outer_attributes(&ti.attrs)?;
         match ti.node {
             hir::TraitItemKind::Const(ref ty, default) => {
@@ -938,7 +938,7 @@ impl<'a> State<'a> {
     pub fn print_impl_item(&mut self, ii: &hir::ImplItem) -> io::Result<()> {
         self.ann.pre(self, NodeSubItem(ii.id))?;
         self.hardbreak_if_not_bol()?;
-        self.maybe_print_comment(ii.span.lo)?;
+        self.maybe_print_comment(ii.span.lo())?;
         self.print_outer_attributes(&ii.attrs)?;
         self.print_defaultness(ii.defaultness)?;
 
@@ -962,7 +962,7 @@ impl<'a> State<'a> {
     }
 
     pub fn print_stmt(&mut self, st: &hir::Stmt) -> io::Result<()> {
-        self.maybe_print_comment(st.span.lo)?;
+        self.maybe_print_comment(st.span.lo())?;
         match st.node {
             hir::StmtDecl(ref decl, _) => {
                 self.print_decl(&decl)?;
@@ -1017,7 +1017,7 @@ impl<'a> State<'a> {
             hir::PopUnsafeBlock(..) => self.word_space("pop_unsafe")?,
             hir::DefaultBlock => (),
         }
-        self.maybe_print_comment(blk.span.lo)?;
+        self.maybe_print_comment(blk.span.lo())?;
         self.ann.pre(self, NodeBlock(blk))?;
         self.bopen()?;
 
@@ -1030,7 +1030,7 @@ impl<'a> State<'a> {
             Some(ref expr) => {
                 self.space_if_not_bol()?;
                 self.print_expr(&expr)?;
-                self.maybe_print_trailing_comment(expr.span, Some(blk.span.hi))?;
+                self.maybe_print_trailing_comment(expr.span, Some(blk.span.hi()))?;
             }
             _ => (),
         }
@@ -1228,7 +1228,7 @@ impl<'a> State<'a> {
     }
 
     pub fn print_expr(&mut self, expr: &hir::Expr) -> io::Result<()> {
-        self.maybe_print_comment(expr.span.lo)?;
+        self.maybe_print_comment(expr.span.lo())?;
         self.print_outer_attributes(&expr.attrs)?;
         self.ibox(indent_unit)?;
         self.ann.pre(self, NodeExpr(expr))?;
@@ -1312,7 +1312,7 @@ impl<'a> State<'a> {
                 }
                 self.bclose_(expr.span, indent_unit)?;
             }
-            hir::ExprClosure(capture_clause, ref decl, body, _fn_decl_span) => {
+            hir::ExprClosure(capture_clause, ref decl, body, _fn_decl_span, _gen) => {
                 self.print_capture_clause(capture_clause)?;
 
                 self.print_closure_args(&decl, body)?;
@@ -1461,6 +1461,10 @@ impl<'a> State<'a> {
 
                 self.pclose()?;
             }
+            hir::ExprYield(ref expr) => {
+                self.s.word("yield")?;
+                self.print_expr(&expr)?;
+            }
         }
         self.ann.post(self, NodeExpr(expr))?;
         self.end()
@@ -1476,7 +1480,7 @@ impl<'a> State<'a> {
     }
 
     pub fn print_decl(&mut self, decl: &hir::Decl) -> io::Result<()> {
-        self.maybe_print_comment(decl.span.lo)?;
+        self.maybe_print_comment(decl.span.lo())?;
         match decl.node {
             hir::DeclLocal(ref loc) => {
                 self.space_if_not_bol()?;
@@ -1519,7 +1523,7 @@ impl<'a> State<'a> {
                       path: &hir::Path,
                       colons_before_params: bool)
                       -> io::Result<()> {
-        self.maybe_print_comment(path.span.lo)?;
+        self.maybe_print_comment(path.span.lo())?;
 
         for (i, segment) in path.segments.iter().enumerate() {
             if i > 0 {
@@ -1637,7 +1641,7 @@ impl<'a> State<'a> {
     }
 
     pub fn print_pat(&mut self, pat: &hir::Pat) -> io::Result<()> {
-        self.maybe_print_comment(pat.span.lo)?;
+        self.maybe_print_comment(pat.span.lo())?;
         self.ann.pre(self, NodePat(pat))?;
         // Pat isn't normalized, but the beauty of it
         // is that it doesn't matter
@@ -1893,7 +1897,7 @@ impl<'a> State<'a> {
         match decl.output {
             hir::Return(ref ty) => {
                 self.print_type(&ty)?;
-                self.maybe_print_comment(ty.span.lo)
+                self.maybe_print_comment(ty.span.lo())
             }
             hir::DefaultReturn(..) => unreachable!(),
         }
@@ -2070,7 +2074,7 @@ impl<'a> State<'a> {
         self.end()?;
 
         match decl.output {
-            hir::Return(ref output) => self.maybe_print_comment(output.span.lo),
+            hir::Return(ref output) => self.maybe_print_comment(output.span.lo()),
             _ => Ok(()),
         }
     }
@@ -2120,13 +2124,13 @@ impl<'a> State<'a> {
             if (*cmnt).style != comments::Trailing {
                 return Ok(());
             }
-            let span_line = cm.lookup_char_pos(span.hi);
+            let span_line = cm.lookup_char_pos(span.hi());
             let comment_line = cm.lookup_char_pos((*cmnt).pos);
             let mut next = (*cmnt).pos + BytePos(1);
             if let Some(p) = next_pos {
                 next = p;
             }
-            if span.hi < (*cmnt).pos && (*cmnt).pos < next &&
+            if span.hi() < (*cmnt).pos && (*cmnt).pos < next &&
                span_line.line == comment_line.line {
                 self.print_comment(cmnt)?;
             }
diff --git a/src/librustc/ich/hcx.rs b/src/librustc/ich/hcx.rs
index 218483232d673..9c841022fcb82 100644
--- a/src/librustc/ich/hcx.rs
+++ b/src/librustc/ich/hcx.rs
@@ -205,13 +205,15 @@ impl<'a, 'gcx, 'tcx> HashStable<StableHashingContext<'a, 'gcx, 'tcx>> for ast::N
                 // corresponding entry in the `trait_map` we need to hash that.
                 // Make sure we don't ignore too much by checking that there is
                 // no entry in a debug_assert!().
-                debug_assert!(hcx.tcx.trait_map.get(self).is_none());
+                let hir_id = hcx.tcx.hir.node_to_hir_id(*self);
+                debug_assert!(hcx.tcx.in_scope_traits(hir_id).is_none());
             }
             NodeIdHashingMode::HashDefPath => {
                 hcx.tcx.hir.definitions().node_to_hir_id(*self).hash_stable(hcx, hasher);
             }
             NodeIdHashingMode::HashTraitsInScope => {
-                if let Some(traits) = hcx.tcx.trait_map.get(self) {
+                let hir_id = hcx.tcx.hir.node_to_hir_id(*self);
+                if let Some(traits) = hcx.tcx.in_scope_traits(hir_id) {
                     // The ordering of the candidates is not fixed. So we hash
                     // the def-ids and then sort them and hash the collection.
                     let mut candidates: AccumulateVec<[_; 8]> =
@@ -253,17 +255,17 @@ impl<'a, 'gcx, 'tcx> HashStable<StableHashingContext<'a, 'gcx, 'tcx>> for Span {
         // If this is not an empty or invalid span, we want to hash the last
         // position that belongs to it, as opposed to hashing the first
         // position past it.
-        let span_hi = if self.hi > self.lo {
+        let span_hi = if self.hi() > self.lo() {
             // We might end up in the middle of a multibyte character here,
             // but that's OK, since we are not trying to decode anything at
             // this position.
-            self.hi - ::syntax_pos::BytePos(1)
+            self.hi() - ::syntax_pos::BytePos(1)
         } else {
-            self.hi
+            self.hi()
         };
 
         {
-            let loc1 = hcx.codemap().byte_pos_to_line_and_col(self.lo);
+            let loc1 = hcx.codemap().byte_pos_to_line_and_col(self.lo());
             let loc1 = loc1.as_ref()
                            .map(|&(ref fm, line, col)| (&fm.name[..], line, col.to_usize()))
                            .unwrap_or(("???", 0, 0));
@@ -296,7 +298,7 @@ impl<'a, 'gcx, 'tcx> HashStable<StableHashingContext<'a, 'gcx, 'tcx>> for Span {
             }
         }
 
-        if self.ctxt == SyntaxContext::empty() {
+        if self.ctxt() == SyntaxContext::empty() {
             0u8.hash_stable(hcx, hasher);
         } else {
             1u8.hash_stable(hcx, hasher);
diff --git a/src/librustc/ich/impls_hir.rs b/src/librustc/ich/impls_hir.rs
index a79133187895a..411f5e26e4d05 100644
--- a/src/librustc/ich/impls_hir.rs
+++ b/src/librustc/ich/impls_hir.rs
@@ -569,6 +569,7 @@ impl<'a, 'gcx, 'tcx> HashStable<StableHashingContext<'a, 'gcx, 'tcx>> for hir::E
                 hir::ExprBreak(..)      |
                 hir::ExprAgain(..)      |
                 hir::ExprRet(..)        |
+                hir::ExprYield(..)    |
                 hir::ExprInlineAsm(..)  |
                 hir::ExprRepeat(..)     |
                 hir::ExprTup(..)        => {
@@ -633,7 +634,7 @@ impl_stable_hash_for!(enum hir::Expr_ {
     ExprWhile(cond, body, label),
     ExprLoop(body, label, loop_src),
     ExprMatch(matchee, arms, match_src),
-    ExprClosure(capture_clause, decl, body_id, span),
+    ExprClosure(capture_clause, decl, body_id, span, gen),
     ExprBlock(blk),
     ExprAssign(lhs, rhs),
     ExprAssignOp(op, lhs, rhs),
@@ -647,7 +648,8 @@ impl_stable_hash_for!(enum hir::Expr_ {
     ExprRet(val),
     ExprInlineAsm(asm, inputs, outputs),
     ExprStruct(path, fields, base),
-    ExprRepeat(val, times)
+    ExprRepeat(val, times),
+    ExprYield(val)
 });
 
 impl_stable_hash_for!(enum hir::LocalSource {
@@ -1024,7 +1026,8 @@ impl_stable_hash_for!(struct hir::Arg {
 
 impl_stable_hash_for!(struct hir::Body {
     arguments,
-    value
+    value,
+    is_generator
 });
 
 impl<'a, 'gcx, 'tcx> HashStable<StableHashingContext<'a, 'gcx, 'tcx>> for hir::BodyId {
diff --git a/src/librustc/ich/impls_mir.rs b/src/librustc/ich/impls_mir.rs
index faf579186e5fc..9a061da177eba 100644
--- a/src/librustc/ich/impls_mir.rs
+++ b/src/librustc/ich/impls_mir.rs
@@ -17,7 +17,7 @@ use rustc_data_structures::stable_hasher::{HashStable, StableHasher,
                                            StableHasherResult};
 use std::mem;
 
-
+impl_stable_hash_for!(struct mir::GeneratorLayout<'tcx> { fields });
 impl_stable_hash_for!(struct mir::SourceInfo { span, scope });
 impl_stable_hash_for!(enum mir::Mutability { Mut, Not });
 impl_stable_hash_for!(enum mir::BorrowKind { Shared, Unique, Mut });
@@ -27,6 +27,7 @@ impl_stable_hash_for!(struct mir::LocalDecl<'tcx> {
     ty,
     name,
     source_info,
+    internal,
     is_user_variable
 });
 impl_stable_hash_for!(struct mir::UpvarDecl { debug_name, by_ref });
@@ -54,9 +55,11 @@ for mir::Terminator<'gcx> {
             mir::TerminatorKind::SwitchInt { .. } |
             mir::TerminatorKind::Resume |
             mir::TerminatorKind::Return |
+            mir::TerminatorKind::GeneratorDrop |
             mir::TerminatorKind::Unreachable |
             mir::TerminatorKind::Drop { .. } |
             mir::TerminatorKind::DropAndReplace { .. } |
+            mir::TerminatorKind::Yield { .. } |
             mir::TerminatorKind::Call { .. } => false,
         };
 
@@ -146,6 +149,7 @@ for mir::TerminatorKind<'gcx> {
             }
             mir::TerminatorKind::Resume |
             mir::TerminatorKind::Return |
+            mir::TerminatorKind::GeneratorDrop |
             mir::TerminatorKind::Unreachable => {}
             mir::TerminatorKind::Drop { ref location, target, unwind } => {
                 location.hash_stable(hcx, hasher);
@@ -161,6 +165,13 @@ for mir::TerminatorKind<'gcx> {
                 target.hash_stable(hcx, hasher);
                 unwind.hash_stable(hcx, hasher);
             }
+            mir::TerminatorKind::Yield { ref value,
+                                        resume,
+                                        drop } => {
+                value.hash_stable(hcx, hasher);
+                resume.hash_stable(hcx, hasher);
+                drop.hash_stable(hcx, hasher);
+            }
             mir::TerminatorKind::Call { ref func,
                                         ref args,
                                         ref destination,
@@ -200,6 +211,8 @@ for mir::AssertMessage<'gcx> {
             mir::AssertMessage::Math(ref const_math_err) => {
                 const_math_err.hash_stable(hcx, hasher);
             }
+            mir::AssertMessage::GeneratorResumedAfterReturn => (),
+            mir::AssertMessage::GeneratorResumedAfterPanic => (),
         }
     }
 }
@@ -226,8 +239,8 @@ for mir::StatementKind<'gcx> {
             mir::StatementKind::StorageDead(ref lvalue) => {
                 lvalue.hash_stable(hcx, hasher);
             }
-            mir::StatementKind::EndRegion(ref extent) => {
-                extent.hash_stable(hcx, hasher);
+            mir::StatementKind::EndRegion(ref region_scope) => {
+                region_scope.hash_stable(hcx, hasher);
             }
             mir::StatementKind::Validate(ref op, ref lvalues) => {
                 op.hash_stable(hcx, hasher);
@@ -258,7 +271,7 @@ impl<'a, 'gcx, 'tcx, T> HashStable<StableHashingContext<'a, 'gcx, 'tcx>>
     }
 }
 
-impl_stable_hash_for!(enum mir::ValidationOp { Acquire, Release, Suspend(extent) });
+impl_stable_hash_for!(enum mir::ValidationOp { Acquire, Release, Suspend(region_scope) });
 
 impl<'a, 'gcx, 'tcx> HashStable<StableHashingContext<'a, 'gcx, 'tcx>> for mir::Lvalue<'gcx> {
     fn hash_stable<W: StableHasherResult>(&self,
@@ -433,6 +446,11 @@ for mir::AggregateKind<'gcx> {
                 def_id.hash_stable(hcx, hasher);
                 substs.hash_stable(hcx, hasher);
             }
+            mir::AggregateKind::Generator(def_id, ref substs, ref interior) => {
+                def_id.hash_stable(hcx, hasher);
+                substs.hash_stable(hcx, hasher);
+                interior.hash_stable(hcx, hasher);
+            }
         }
     }
 }
diff --git a/src/librustc/ich/impls_ty.rs b/src/librustc/ich/impls_ty.rs
index 5f51579945e33..077905b3ac0ae 100644
--- a/src/librustc/ich/impls_ty.rs
+++ b/src/librustc/ich/impls_ty.rs
@@ -17,6 +17,7 @@ use rustc_data_structures::stable_hasher::{HashStable, StableHasher,
 use std::hash as std_hash;
 use std::mem;
 use syntax_pos::symbol::InternedString;
+use middle::region;
 use ty;
 
 impl<'a, 'gcx, 'tcx, T> HashStable<StableHashingContext<'a, 'gcx, 'tcx>>
@@ -65,8 +66,8 @@ for ty::RegionKind {
                 index.hash_stable(hcx, hasher);
                 name.hash_stable(hcx, hasher);
             }
-            ty::ReScope(code_extent) => {
-                code_extent.hash_stable(hcx, hasher);
+            ty::ReScope(scope) => {
+                scope.hash_stable(hcx, hasher);
             }
             ty::ReFree(ref free_region) => {
                 free_region.hash_stable(hcx, hasher);
@@ -147,6 +148,11 @@ for ty::UpvarCapture<'gcx> {
     }
 }
 
+impl_stable_hash_for!(struct ty::GenSig<'tcx> {
+    yield_ty,
+    return_ty
+});
+
 impl_stable_hash_for!(struct ty::FnSig<'tcx> {
     inputs_and_output,
     variadic,
@@ -321,6 +327,8 @@ for ::middle::const_val::ConstVal<'gcx> {
 
 impl_stable_hash_for!(struct ty::ClosureSubsts<'tcx> { substs });
 
+impl_stable_hash_for!(struct ty::GeneratorInterior<'tcx> { witness });
+
 impl_stable_hash_for!(struct ty::GenericPredicates<'tcx> {
     parent,
     predicates
@@ -443,24 +451,22 @@ impl_stable_hash_for!(enum ty::cast::CastKind {
 });
 
 impl<'a, 'gcx, 'tcx> HashStable<StableHashingContext<'a, 'gcx, 'tcx>>
-for ::middle::region::CodeExtent
+for region::Scope
 {
     fn hash_stable<W: StableHasherResult>(&self,
                                           hcx: &mut StableHashingContext<'a, 'gcx, 'tcx>,
                                           hasher: &mut StableHasher<W>) {
-        use middle::region::CodeExtent;
-
         mem::discriminant(self).hash_stable(hcx, hasher);
         match *self {
-            CodeExtent::Misc(node_id) |
-            CodeExtent::DestructionScope(node_id) => {
+            region::Scope::Node(node_id) |
+            region::Scope::Destruction(node_id) => {
                 node_id.hash_stable(hcx, hasher);
             }
-            CodeExtent::CallSiteScope(body_id) |
-            CodeExtent::ParameterScope(body_id) => {
+            region::Scope::CallSite(body_id) |
+            region::Scope::Arguments(body_id) => {
                 body_id.hash_stable(hcx, hasher);
             }
-            CodeExtent::Remainder(block_remainder) => {
+            region::Scope::Remainder(block_remainder) => {
                 block_remainder.hash_stable(hcx, hasher);
             }
         }
@@ -546,6 +552,12 @@ for ty::TypeVariants<'gcx>
                 def_id.hash_stable(hcx, hasher);
                 closure_substs.hash_stable(hcx, hasher);
             }
+            TyGenerator(def_id, closure_substs, interior)
+             => {
+                def_id.hash_stable(hcx, hasher);
+                closure_substs.hash_stable(hcx, hasher);
+                interior.hash_stable(hcx, hasher);
+            }
             TyTuple(inner_tys, from_diverging_type_var) => {
                 inner_tys.hash_stable(hcx, hasher);
                 from_diverging_type_var.hash_stable(hcx, hasher);
@@ -625,6 +637,7 @@ impl_stable_hash_for!(enum ty::fast_reject::SimplifiedType {
     TupleSimplifiedType(size),
     TraitSimplifiedType(def_id),
     ClosureSimplifiedType(def_id),
+    GeneratorSimplifiedType(def_id),
     AnonSimplifiedType(def_id),
     FunctionSimplifiedType(params),
     ParameterSimplifiedType
diff --git a/src/librustc/infer/error_reporting/mod.rs b/src/librustc/infer/error_reporting/mod.rs
index edf9ca89b3394..476bf94714268 100644
--- a/src/librustc/infer/error_reporting/mod.rs
+++ b/src/librustc/infer/error_reporting/mod.rs
@@ -83,6 +83,7 @@ mod anon_anon_conflict;
 
 impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
     pub fn note_and_explain_region(self,
+                                   region_scope_tree: &region::ScopeTree,
                                    err: &mut DiagnosticBuilder,
                                    prefix: &str,
                                    region: ty::Region<'tcx>,
@@ -118,7 +119,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
         fn explain_span<'a, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
                                         heading: &str, span: Span)
                                         -> (String, Option<Span>) {
-            let lo = tcx.sess.codemap().lookup_char_pos_adj(span.lo);
+            let lo = tcx.sess.codemap().lookup_char_pos_adj(span.lo());
             (format!("the {} at {}:{}", heading, lo.line, lo.col.to_usize() + 1),
              Some(span))
         }
@@ -130,14 +131,8 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
                     format!("{}unknown scope: {:?}{}.  Please report a bug.",
                             prefix, scope, suffix)
                 };
-                let span = match scope.span(&self.hir) {
-                    Some(s) => s,
-                    None => {
-                        err.note(&unknown_scope());
-                        return;
-                    }
-                };
-                let tag = match self.hir.find(scope.node_id()) {
+                let span = scope.span(self, region_scope_tree);
+                let tag = match self.hir.find(scope.node_id(self, region_scope_tree)) {
                     Some(hir_map::NodeBlock(_)) => "block",
                     Some(hir_map::NodeExpr(expr)) => match expr.node {
                         hir::ExprCall(..) => "call",
@@ -158,18 +153,18 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
                     }
                 };
                 let scope_decorated_tag = match scope {
-                    region::CodeExtent::Misc(_) => tag,
-                    region::CodeExtent::CallSiteScope(_) => {
+                    region::Scope::Node(_) => tag,
+                    region::Scope::CallSite(_) => {
                         "scope of call-site for function"
                     }
-                    region::CodeExtent::ParameterScope(_) => {
+                    region::Scope::Arguments(_) => {
                         "scope of function body"
                     }
-                    region::CodeExtent::DestructionScope(_) => {
+                    region::Scope::Destruction(_) => {
                         new_string = format!("destruction scope surrounding {}", tag);
                         &new_string[..]
                     }
-                    region::CodeExtent::Remainder(r) => {
+                    region::Scope::Remainder(r) => {
                         new_string = format!("block suffix following statement {}",
                                              r.first_statement_index);
                         &new_string[..]
@@ -260,8 +255,9 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
 }
 
 impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
-
-    pub fn report_region_errors(&self, errors: &Vec<RegionResolutionError<'tcx>>) {
+    pub fn report_region_errors(&self,
+                                region_scope_tree: &region::ScopeTree,
+                                errors: &Vec<RegionResolutionError<'tcx>>) {
         debug!("report_region_errors(): {} errors to start", errors.len());
 
         // try to pre-process the errors, which will group some of them
@@ -285,16 +281,16 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                   // the error. If all of these fails, we fall back to a rather
                   // general bit of code that displays the error information
                   ConcreteFailure(origin, sub, sup) => {
-
-                      self.report_concrete_failure(origin, sub, sup).emit();
+                      self.report_concrete_failure(region_scope_tree, origin, sub, sup).emit();
                   }
 
                   GenericBoundFailure(kind, param_ty, sub) => {
-                      self.report_generic_bound_failure(kind, param_ty, sub);
+                      self.report_generic_bound_failure(region_scope_tree, kind, param_ty, sub);
                   }
 
                   SubSupConflict(var_origin, sub_origin, sub_r, sup_origin, sup_r) => {
-                        self.report_sub_sup_conflict(var_origin,
+                        self.report_sub_sup_conflict(region_scope_tree,
+                                                     var_origin,
                                                      sub_origin,
                                                      sub_r,
                                                      sup_origin,
@@ -773,6 +769,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
     }
 
     fn report_generic_bound_failure(&self,
+                                    region_scope_tree: &region::ScopeTree,
                                     origin: SubregionOrigin<'tcx>,
                                     bound_kind: GenericKind<'tcx>,
                                     sub: Region<'tcx>)
@@ -840,6 +837,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                 err.help(&format!("consider adding an explicit lifetime bound for `{}`",
                                   bound_kind));
                 self.tcx.note_and_explain_region(
+                    region_scope_tree,
                     &mut err,
                     &format!("{} must be valid for ", labeled_user_string),
                     sub,
@@ -853,6 +851,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
     }
 
     fn report_sub_sup_conflict(&self,
+                               region_scope_tree: &region::ScopeTree,
                                var_origin: RegionVariableOrigin,
                                sub_origin: SubregionOrigin<'tcx>,
                                sub_region: Region<'tcx>,
@@ -860,14 +859,14 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                                sup_region: Region<'tcx>) {
         let mut err = self.report_inference_failure(var_origin);
 
-        self.tcx.note_and_explain_region(&mut err,
+        self.tcx.note_and_explain_region(region_scope_tree, &mut err,
             "first, the lifetime cannot outlive ",
             sup_region,
             "...");
 
         self.note_region_origin(&mut err, &sup_origin);
 
-        self.tcx.note_and_explain_region(&mut err,
+        self.tcx.note_and_explain_region(region_scope_tree, &mut err,
             "but, the lifetime must be valid for ",
             sub_region,
             "...");
diff --git a/src/librustc/infer/error_reporting/note.rs b/src/librustc/infer/error_reporting/note.rs
index 87047d0df144c..68e8ccbc3d886 100644
--- a/src/librustc/infer/error_reporting/note.rs
+++ b/src/librustc/infer/error_reporting/note.rs
@@ -9,6 +9,7 @@
 // except according to those terms.
 
 use infer::{self, InferCtxt, SubregionOrigin};
+use middle::region;
 use ty::{self, Region};
 use ty::error::TypeError;
 use errors::DiagnosticBuilder;
@@ -144,6 +145,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
     }
 
     pub(super) fn report_concrete_failure(&self,
+                                          region_scope_tree: &region::ScopeTree,
                                           origin: SubregionOrigin<'tcx>,
                                           sub: Region<'tcx>,
                                           sup: Region<'tcx>)
@@ -151,7 +153,11 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
         match origin {
             infer::Subtype(trace) => {
                 let terr = TypeError::RegionsDoesNotOutlive(sup, sub);
-                self.report_and_explain_type_error(trace, &terr)
+                let mut err = self.report_and_explain_type_error(trace, &terr);
+                self.tcx.note_and_explain_region(region_scope_tree, &mut err, "", sup, "...");
+                self.tcx.note_and_explain_region(region_scope_tree, &mut err,
+                    "...does not necessarily outlive ", sub, "");
+                err
             }
             infer::Reborrow(span) => {
                 let mut err = struct_span_err!(self.tcx.sess,
@@ -159,11 +165,11 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                                                E0312,
                                                "lifetime of reference outlives lifetime of \
                                                 borrowed content...");
-                self.tcx.note_and_explain_region(&mut err,
+                self.tcx.note_and_explain_region(region_scope_tree, &mut err,
                                                  "...the reference is valid for ",
                                                  sub,
                                                  "...");
-                self.tcx.note_and_explain_region(&mut err,
+                self.tcx.note_and_explain_region(region_scope_tree, &mut err,
                                                  "...but the borrowed content is only valid for ",
                                                  sup,
                                                  "");
@@ -177,27 +183,27 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                                                 of captured variable `{}`...",
                                                self.tcx
                                                    .local_var_name_str_def_index(upvar_id.var_id));
-                self.tcx.note_and_explain_region(&mut err,
+                self.tcx.note_and_explain_region(region_scope_tree, &mut err,
                                                  "...the borrowed pointer is valid for ",
                                                  sub,
                                                  "...");
-                self.tcx
-                    .note_and_explain_region(
-                      &mut err,
-                      &format!("...but `{}` is only valid for ",
-                               self.tcx.local_var_name_str_def_index(upvar_id.var_id)),
-                      sup,
-                      "");
+                self.tcx.note_and_explain_region(
+                    region_scope_tree,
+                    &mut err,
+                    &format!("...but `{}` is only valid for ",
+                        self.tcx.local_var_name_str_def_index(upvar_id.var_id)),
+                    sup,
+                    "");
                 err
             }
             infer::InfStackClosure(span) => {
                 let mut err =
                     struct_span_err!(self.tcx.sess, span, E0314, "closure outlives stack frame");
-                self.tcx.note_and_explain_region(&mut err,
+                self.tcx.note_and_explain_region(region_scope_tree, &mut err,
                                                  "...the closure must be valid for ",
                                                  sub,
                                                  "...");
-                self.tcx.note_and_explain_region(&mut err,
+                self.tcx.note_and_explain_region(region_scope_tree, &mut err,
                                                  "...but the closure's stack frame is only valid \
                                                   for ",
                                                  sup,
@@ -209,8 +215,8 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                                                span,
                                                E0315,
                                                "cannot invoke closure outside of its lifetime");
-                self.tcx
-                    .note_and_explain_region(&mut err, "the closure is only valid for ", sup, "");
+                self.tcx.note_and_explain_region(region_scope_tree, &mut err,
+                    "the closure is only valid for ", sup, "");
                 err
             }
             infer::DerefPointer(span) => {
@@ -218,8 +224,8 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                                                span,
                                                E0473,
                                                "dereference of reference outside its lifetime");
-                self.tcx
-                    .note_and_explain_region(&mut err, "the reference is only valid for ", sup, "");
+                self.tcx.note_and_explain_region(region_scope_tree, &mut err,
+                    "the reference is only valid for ", sup, "");
                 err
             }
             infer::FreeVariable(span, id) => {
@@ -229,9 +235,10 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                                                "captured variable `{}` does not outlive the \
                                                 enclosing closure",
                                                self.tcx.local_var_name_str(id));
-                self.tcx
-                    .note_and_explain_region(&mut err, "captured variable is valid for ", sup, "");
-                self.tcx.note_and_explain_region(&mut err, "closure is valid for ", sub, "");
+                self.tcx.note_and_explain_region(region_scope_tree, &mut err,
+                    "captured variable is valid for ", sup, "");
+                self.tcx.note_and_explain_region(region_scope_tree, &mut err,
+                    "closure is valid for ", sub, "");
                 err
             }
             infer::IndexSlice(span) => {
@@ -239,7 +246,8 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                                                span,
                                                E0475,
                                                "index of slice outside its lifetime");
-                self.tcx.note_and_explain_region(&mut err, "the slice is only valid for ", sup, "");
+                self.tcx.note_and_explain_region(region_scope_tree, &mut err,
+                    "the slice is only valid for ", sup, "");
                 err
             }
             infer::RelateObjectBound(span) => {
@@ -248,8 +256,9 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                                                E0476,
                                                "lifetime of the source pointer does not outlive \
                                                 lifetime bound of the object type");
-                self.tcx.note_and_explain_region(&mut err, "object type is valid for ", sub, "");
-                self.tcx.note_and_explain_region(&mut err,
+                self.tcx.note_and_explain_region(region_scope_tree, &mut err,
+                    "object type is valid for ", sub, "");
+                self.tcx.note_and_explain_region(region_scope_tree, &mut err,
                                                  "source pointer is only valid for ",
                                                  sup,
                                                  "");
@@ -264,10 +273,12 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                                                self.ty_to_string(ty));
                 match *sub {
                     ty::ReStatic => {
-                        self.tcx.note_and_explain_region(&mut err, "type must satisfy ", sub, "")
+                        self.tcx.note_and_explain_region(region_scope_tree, &mut err,
+                            "type must satisfy ", sub, "")
                     }
                     _ => {
-                        self.tcx.note_and_explain_region(&mut err, "type must outlive ", sub, "")
+                        self.tcx.note_and_explain_region(region_scope_tree, &mut err,
+                            "type must outlive ", sub, "")
                     }
                 }
                 err
@@ -275,11 +286,11 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
             infer::RelateRegionParamBound(span) => {
                 let mut err =
                     struct_span_err!(self.tcx.sess, span, E0478, "lifetime bound not satisfied");
-                self.tcx.note_and_explain_region(&mut err,
+                self.tcx.note_and_explain_region(region_scope_tree, &mut err,
                                                  "lifetime parameter instantiated with ",
                                                  sup,
                                                  "");
-                self.tcx.note_and_explain_region(&mut err,
+                self.tcx.note_and_explain_region(region_scope_tree, &mut err,
                                                  "but lifetime parameter must outlive ",
                                                  sub,
                                                  "");
@@ -292,7 +303,8 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                                                "the type `{}` (provided as the value of a type \
                                                 parameter) is not valid at this point",
                                                self.ty_to_string(ty));
-                self.tcx.note_and_explain_region(&mut err, "type must outlive ", sub, "");
+                self.tcx.note_and_explain_region(region_scope_tree, &mut err,
+                    "type must outlive ", sub, "");
                 err
             }
             infer::CallRcvr(span) => {
@@ -301,8 +313,8 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                                                E0480,
                                                "lifetime of method receiver does not outlive the \
                                                 method call");
-                self.tcx
-                    .note_and_explain_region(&mut err, "the receiver is only valid for ", sup, "");
+                self.tcx.note_and_explain_region(region_scope_tree, &mut err,
+                "the receiver is only valid for ", sup, "");
                 err
             }
             infer::CallArg(span) => {
@@ -311,7 +323,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                                                E0481,
                                                "lifetime of function argument does not outlive \
                                                 the function call");
-                self.tcx.note_and_explain_region(&mut err,
+                self.tcx.note_and_explain_region(region_scope_tree, &mut err,
                                                  "the function argument is only valid for ",
                                                  sup,
                                                  "");
@@ -323,7 +335,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                                                E0482,
                                                "lifetime of return value does not outlive the \
                                                 function call");
-                self.tcx.note_and_explain_region(&mut err,
+                self.tcx.note_and_explain_region(region_scope_tree, &mut err,
                                                  "the return value is only valid for ",
                                                  sup,
                                                  "");
@@ -335,8 +347,8 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                                                E0483,
                                                "lifetime of operand does not outlive the \
                                                 operation");
-                self.tcx
-                    .note_and_explain_region(&mut err, "the operand is only valid for ", sup, "");
+                self.tcx.note_and_explain_region(region_scope_tree, &mut err,
+                    "the operand is only valid for ", sup, "");
                 err
             }
             infer::AddrOf(span) => {
@@ -344,8 +356,8 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                                                span,
                                                E0484,
                                                "reference is not valid at the time of borrow");
-                self.tcx
-                    .note_and_explain_region(&mut err, "the borrow is only valid for ", sup, "");
+                self.tcx.note_and_explain_region(region_scope_tree, &mut err,
+                    "the borrow is only valid for ", sup, "");
                 err
             }
             infer::AutoBorrow(span) => {
@@ -354,7 +366,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                                                E0485,
                                                "automatically reference is not valid at the time \
                                                 of borrow");
-                self.tcx.note_and_explain_region(&mut err,
+                self.tcx.note_and_explain_region(region_scope_tree, &mut err,
                                                  "the automatic borrow is only valid for ",
                                                  sup,
                                                  "");
@@ -367,7 +379,8 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                                                "type of expression contains references that are \
                                                 not valid during the expression: `{}`",
                                                self.ty_to_string(t));
-                self.tcx.note_and_explain_region(&mut err, "type is only valid for ", sup, "");
+                self.tcx.note_and_explain_region(region_scope_tree, &mut err,
+                    "type is only valid for ", sup, "");
                 err
             }
             infer::SafeDestructor(span) => {
@@ -377,8 +390,10 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                                                "unsafe use of destructor: destructor might be \
                                                 called while references are dead");
                 // FIXME (22171): terms "super/subregion" are suboptimal
-                self.tcx.note_and_explain_region(&mut err, "superregion: ", sup, "");
-                self.tcx.note_and_explain_region(&mut err, "subregion: ", sub, "");
+                self.tcx.note_and_explain_region(region_scope_tree, &mut err,
+                    "superregion: ", sup, "");
+                self.tcx.note_and_explain_region(region_scope_tree, &mut err,
+                    "subregion: ", sub, "");
                 err
             }
             infer::BindingTypeIsNotValidAtDecl(span) => {
@@ -387,8 +402,8 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                                                E0488,
                                                "lifetime of variable does not enclose its \
                                                 declaration");
-                self.tcx
-                    .note_and_explain_region(&mut err, "the variable is only valid for ", sup, "");
+                self.tcx.note_and_explain_region(region_scope_tree, &mut err,
+                    "the variable is only valid for ", sup, "");
                 err
             }
             infer::ParameterInScope(_, span) => {
@@ -396,8 +411,8 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                                                span,
                                                E0489,
                                                "type/lifetime parameter not in scope here");
-                self.tcx
-                    .note_and_explain_region(&mut err, "the parameter is only valid for ", sub, "");
+                self.tcx.note_and_explain_region(region_scope_tree, &mut err,
+                    "the parameter is only valid for ", sub, "");
                 err
             }
             infer::DataBorrowed(ty, span) => {
@@ -406,8 +421,10 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                                                E0490,
                                                "a value of type `{}` is borrowed for too long",
                                                self.ty_to_string(ty));
-                self.tcx.note_and_explain_region(&mut err, "the type is valid for ", sub, "");
-                self.tcx.note_and_explain_region(&mut err, "but the borrow lasts for ", sup, "");
+                self.tcx.note_and_explain_region(region_scope_tree, &mut err,
+                    "the type is valid for ", sub, "");
+                self.tcx.note_and_explain_region(region_scope_tree, &mut err,
+                    "but the borrow lasts for ", sup, "");
                 err
             }
             infer::ReferenceOutlivesReferent(ty, span) => {
@@ -417,8 +434,9 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                                                "in type `{}`, reference has a longer lifetime \
                                                 than the data it references",
                                                self.ty_to_string(ty));
-                self.tcx.note_and_explain_region(&mut err, "the pointer is valid for ", sub, "");
-                self.tcx.note_and_explain_region(&mut err,
+                self.tcx.note_and_explain_region(region_scope_tree, &mut err,
+                    "the pointer is valid for ", sub, "");
+                self.tcx.note_and_explain_region(region_scope_tree, &mut err,
                                                  "but the referenced data is only valid for ",
                                                  sup,
                                                  "");
diff --git a/src/librustc/infer/freshen.rs b/src/librustc/infer/freshen.rs
index 41858088f7e70..c274f8bda9fb0 100644
--- a/src/librustc/infer/freshen.rs
+++ b/src/librustc/infer/freshen.rs
@@ -19,10 +19,21 @@
 //! fact an unbound type variable, we want the match to be regarded as ambiguous, because depending
 //! on what type that type variable is ultimately assigned, the match may or may not succeed.
 //!
+//! To handle closures, freshened types also have to contain the signature and kind of any
+//! closure in the local inference context, as otherwise the cache key might be invalidated.
+//! The way this is done is somewhat hacky - the closure signature is appended to the substs,
+//! as well as the closure kind "encoded" as a type. Also, special handling is needed when
+//! the closure signature contains a reference to the original closure.
+//!
 //! Note that you should be careful not to allow the output of freshening to leak to the user in
 //! error messages or in any other form. Freshening is only really useful as an internal detail.
 //!
-//! __An important detail concerning regions.__ The freshener also replaces *all* regions with
+//! Because of the manipulation required to handle closures, doing arbitrary operations on
+//! freshened types is not recommended. However, in addition to doing equality/hash
+//! comparisons (for caching), it is possible to do a `ty::_match` operation between
+//! 2 freshened types - this works even with the closure encoding.
+//!
+//! __An important detail concerning regions.__ The freshener also replaces *all* free regions with
 //! 'erased. The reason behind this is that, in general, we do not take region relationships into
 //! account when making type-overloaded decisions. This is important because of the design of the
 //! region inferencer, which is not based on unification but rather on accumulating and then
@@ -32,7 +43,10 @@
 
 use ty::{self, Ty, TyCtxt, TypeFoldable};
 use ty::fold::TypeFolder;
+use ty::subst::Substs;
 use util::nodemap::FxHashMap;
+use hir::def_id::DefId;
+
 use std::collections::hash_map::Entry;
 
 use super::InferCtxt;
@@ -42,6 +56,7 @@ pub struct TypeFreshener<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
     infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
     freshen_count: u32,
     freshen_map: FxHashMap<ty::InferTy, Ty<'tcx>>,
+    closure_set: Vec<DefId>,
 }
 
 impl<'a, 'gcx, 'tcx> TypeFreshener<'a, 'gcx, 'tcx> {
@@ -51,6 +66,7 @@ impl<'a, 'gcx, 'tcx> TypeFreshener<'a, 'gcx, 'tcx> {
             infcx,
             freshen_count: 0,
             freshen_map: FxHashMap(),
+            closure_set: vec![],
         }
     }
 
@@ -76,6 +92,88 @@ impl<'a, 'gcx, 'tcx> TypeFreshener<'a, 'gcx, 'tcx> {
             }
         }
     }
+
+    fn next_fresh<F>(&mut self,
+                     freshener: F)
+                     -> Ty<'tcx>
+        where F: FnOnce(u32) -> ty::InferTy,
+    {
+        let index = self.freshen_count;
+        self.freshen_count += 1;
+        self.infcx.tcx.mk_infer(freshener(index))
+    }
+
+    fn freshen_closure_like<M, C>(&mut self,
+                                  def_id: DefId,
+                                  substs: ty::ClosureSubsts<'tcx>,
+                                  t: Ty<'tcx>,
+                                  markers: M,
+                                  combine: C)
+                                  -> Ty<'tcx>
+        where M: FnOnce(&mut Self) -> (Ty<'tcx>, Ty<'tcx>),
+              C: FnOnce(&'tcx Substs<'tcx>) -> Ty<'tcx>
+    {
+        let tcx = self.infcx.tcx;
+
+        let closure_in_progress = self.infcx.in_progress_tables.map_or(false, |tables| {
+            tcx.hir.as_local_node_id(def_id).map_or(false, |closure_id| {
+                tables.borrow().local_id_root ==
+                    Some(DefId::local(tcx.hir.node_to_hir_id(closure_id).owner))
+            })
+        });
+
+        if !closure_in_progress {
+            // If this closure belongs to another infcx, its kind etc. were
+            // fully inferred and its signature/kind are exactly what's listed
+            // in its infcx. So we don't need to add the markers for them.
+            return t.super_fold_with(self);
+        }
+
+        // We are encoding a closure in progress. Because we want our freshening
+        // key to contain all inference information needed to make sense of our
+        // value, we need to encode the closure signature and kind. The way
+        // we do that is to add them as 2 variables to the closure substs,
+        // basically because it's there (and nobody cares about adding extra stuff
+        // to substs).
+        //
+        // This means the "freshened" closure substs ends up looking like
+        //     fresh_substs = [PARENT_SUBSTS* ; UPVARS* ; SIG_MARKER ; KIND_MARKER]
+        let (marker_1, marker_2) = if self.closure_set.contains(&def_id) {
+            // We found the closure def-id within its own signature. Just
+            // leave a new freshened type - any matching operations would
+            // have found and compared the exterior closure already to
+            // get here.
+            //
+            // In that case, we already know what the signature would
+            // be - the parent closure on the stack already contains a
+            // "copy" of the signature, so there is no reason to encode
+            // it again for injectivity. Just use a fresh type variable
+            // to make everything comparable.
+            //
+            // For example (closure kinds omitted for clarity)
+            //     t=[closure FOO sig=[closure BAR sig=[closure FOO ..]]]
+            // Would get encoded to
+            //     t=[closure FOO sig=[closure BAR sig=[closure FOO sig=$0]]]
+            //
+            // and we can decode by having
+            //     $0=[closure BAR {sig doesn't exist in decode}]
+            // and get
+            //     t=[closure FOO]
+            //     sig[FOO] = [closure BAR]
+            //     sig[BAR] = [closure FOO]
+            (self.next_fresh(ty::FreshTy), self.next_fresh(ty::FreshTy))
+        } else {
+            self.closure_set.push(def_id);
+            let markers = markers(self);
+            self.closure_set.pop();
+            markers
+        };
+
+        combine(tcx.mk_substs(
+            substs.substs.iter().map(|k| k.fold_with(self)).chain(
+                [marker_1, marker_2].iter().cloned().map(From::from)
+                    )))
+    }
 }
 
 impl<'a, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for TypeFreshener<'a, 'gcx, 'tcx> {
@@ -105,7 +203,8 @@ impl<'a, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for TypeFreshener<'a, 'gcx, 'tcx> {
     }
 
     fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
-        if !t.needs_infer() && !t.has_erasable_regions() {
+        if !t.needs_infer() && !t.has_erasable_regions() &&
+            !(t.has_closure_types() && self.infcx.in_progress_tables.is_some()) {
             return t;
         }
 
@@ -150,6 +249,51 @@ impl<'a, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for TypeFreshener<'a, 'gcx, 'tcx> {
                 t
             }
 
+            ty::TyClosure(def_id, substs) => {
+                self.freshen_closure_like(
+                    def_id, substs, t,
+                    |this| {
+                        // HACK: use a "random" integer type to mark the kind. Because
+                        // different closure kinds shouldn't get unified during
+                        // selection, the "subtyping" relationship (where any kind is
+                        // better than no kind) shouldn't  matter here, just that the
+                        // types are different.
+                        let closure_kind = this.infcx.closure_kind(def_id);
+                        let closure_kind_marker = match closure_kind {
+                            None => tcx.types.i8,
+                            Some(ty::ClosureKind::Fn) => tcx.types.i16,
+                            Some(ty::ClosureKind::FnMut) => tcx.types.i32,
+                            Some(ty::ClosureKind::FnOnce) => tcx.types.i64,
+                        };
+
+                        let closure_sig = this.infcx.fn_sig(def_id);
+                        (tcx.mk_fn_ptr(closure_sig.fold_with(this)),
+                         closure_kind_marker)
+                    },
+                    |substs| tcx.mk_closure(def_id, substs)
+                )
+            }
+
+            ty::TyGenerator(def_id, substs, interior) => {
+                self.freshen_closure_like(
+                    def_id, substs, t,
+                    |this| {
+                        let gen_sig = this.infcx.generator_sig(def_id).unwrap();
+                        // FIXME: want to revise this strategy when generator
+                        // signatures can actually contain LBRs.
+                        let sig = this.tcx().no_late_bound_regions(&gen_sig)
+                            .unwrap_or_else(|| {
+                                bug!("late-bound regions in signature of {:?}",
+                                     def_id)
+                            });
+                        (sig.yield_ty, sig.return_ty).fold_with(this)
+                    },
+                    |substs| {
+                        tcx.mk_generator(def_id, ty::ClosureSubsts { substs }, interior)
+                    }
+                )
+            }
+
             ty::TyBool |
             ty::TyChar |
             ty::TyInt(..) |
@@ -165,7 +309,6 @@ impl<'a, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for TypeFreshener<'a, 'gcx, 'tcx> {
             ty::TyFnDef(..) |
             ty::TyFnPtr(_) |
             ty::TyDynamic(..) |
-            ty::TyClosure(..) |
             ty::TyNever |
             ty::TyTuple(..) |
             ty::TyProjection(..) |
diff --git a/src/librustc/infer/mod.rs b/src/librustc/infer/mod.rs
index 6c9b9d853f403..e85e8e2bdb8c9 100644
--- a/src/librustc/infer/mod.rs
+++ b/src/librustc/infer/mod.rs
@@ -20,7 +20,7 @@ pub use self::region_inference::{GenericKind, VerifyBound};
 
 use hir::def_id::DefId;
 use middle::free_region::{FreeRegionMap, RegionRelations};
-use middle::region::RegionMaps;
+use middle::region;
 use middle::lang_items;
 use mir::tcx::LvalueTy;
 use ty::subst::{Kind, Subst, Substs};
@@ -1070,7 +1070,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
 
     pub fn resolve_regions_and_report_errors(&self,
                                              region_context: DefId,
-                                             region_map: &RegionMaps,
+                                             region_map: &region::ScopeTree,
                                              free_regions: &FreeRegionMap<'tcx>) {
         let region_rels = RegionRelations::new(self.tcx,
                                                region_context,
@@ -1084,7 +1084,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
             // this infcx was in use.  This is totally hokey but
             // otherwise we have a hard time separating legit region
             // errors from silly ones.
-            self.report_region_errors(&errors); // see error_reporting module
+            self.report_region_errors(region_map, &errors); // see error_reporting module
         }
     }
 
@@ -1363,6 +1363,19 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
 
         self.tcx.fn_sig(def_id)
     }
+
+    pub fn generator_sig(&self, def_id: DefId) -> Option<ty::PolyGenSig<'tcx>> {
+        if let Some(tables) = self.in_progress_tables {
+            if let Some(id) = self.tcx.hir.as_local_node_id(def_id) {
+                let hir_id = self.tcx.hir.node_to_hir_id(id);
+                if let Some(&ty) = tables.borrow().generator_sigs().get(hir_id) {
+                    return ty.map(|t| ty::Binder(t));
+                }
+            }
+        }
+
+        self.tcx.generator_sig(def_id)
+    }
 }
 
 impl<'a, 'gcx, 'tcx> TypeTrace<'tcx> {
diff --git a/src/librustc/infer/region_inference/graphviz.rs b/src/librustc/infer/region_inference/graphviz.rs
index 81a8984e7530e..5cf6aa350bdd5 100644
--- a/src/librustc/infer/region_inference/graphviz.rs
+++ b/src/librustc/infer/region_inference/graphviz.rs
@@ -21,7 +21,7 @@ use graphviz as dot;
 use hir::def_id::DefIndex;
 use ty;
 use middle::free_region::RegionRelations;
-use middle::region::CodeExtent;
+use middle::region;
 use super::Constraint;
 use infer::SubregionOrigin;
 use infer::region_inference::RegionVarBindings;
@@ -136,7 +136,7 @@ enum Node {
 #[derive(Clone, PartialEq, Eq, Debug, Copy)]
 enum Edge<'tcx> {
     Constraint(Constraint<'tcx>),
-    EnclScope(CodeExtent, CodeExtent),
+    EnclScope(region::Scope, region::Scope),
 }
 
 impl<'a, 'gcx, 'tcx> ConstraintGraph<'a, 'gcx, 'tcx> {
@@ -159,7 +159,7 @@ impl<'a, 'gcx, 'tcx> ConstraintGraph<'a, 'gcx, 'tcx> {
                 add_node(n2);
             }
 
-            region_rels.region_maps.each_encl_scope(|sub, sup| {
+            region_rels.region_scope_tree.each_encl_scope(|sub, sup| {
                 add_node(Node::Region(ty::ReScope(sub)));
                 add_node(Node::Region(ty::ReScope(sup)));
             });
@@ -245,7 +245,9 @@ impl<'a, 'gcx, 'tcx> dot::GraphWalk<'a> for ConstraintGraph<'a, 'gcx, 'tcx> {
     fn edges(&self) -> dot::Edges<Edge<'tcx>> {
         debug!("constraint graph has {} edges", self.map.len());
         let mut v: Vec<_> = self.map.keys().map(|e| Edge::Constraint(*e)).collect();
-        self.region_rels.region_maps.each_encl_scope(|sub, sup| v.push(Edge::EnclScope(sub, sup)));
+        self.region_rels.region_scope_tree.each_encl_scope(|sub, sup| {
+            v.push(Edge::EnclScope(sub, sup))
+        });
         debug!("region graph has {} edges", v.len());
         Cow::Owned(v)
     }
diff --git a/src/librustc/infer/region_inference/mod.rs b/src/librustc/infer/region_inference/mod.rs
index 5588b6d9add16..8351be490767a 100644
--- a/src/librustc/infer/region_inference/mod.rs
+++ b/src/librustc/infer/region_inference/mod.rs
@@ -935,14 +935,14 @@ impl<'a, 'gcx, 'tcx> RegionVarBindings<'a, 'gcx, 'tcx> {
                 // reasonably compare free regions and scopes:
                 let fr_scope = match (a, b) {
                     (&ReEarlyBound(ref br), _) | (_, &ReEarlyBound(ref br)) => {
-                        region_rels.region_maps.early_free_extent(self.tcx, br)
+                        region_rels.region_scope_tree.early_free_scope(self.tcx, br)
                     }
                     (&ReFree(ref fr), _) | (_, &ReFree(ref fr)) => {
-                        region_rels.region_maps.free_extent(self.tcx, fr)
+                        region_rels.region_scope_tree.free_scope(self.tcx, fr)
                     }
                     _ => bug!()
                 };
-                let r_id = region_rels.region_maps.nearest_common_ancestor(fr_scope, s_id);
+                let r_id = region_rels.region_scope_tree.nearest_common_ancestor(fr_scope, s_id);
                 if r_id == fr_scope {
                     // if the free region's scope `fr.scope` is bigger than
                     // the scope region `s_id`, then the LUB is the free
@@ -963,7 +963,7 @@ impl<'a, 'gcx, 'tcx> RegionVarBindings<'a, 'gcx, 'tcx> {
                 // The region corresponding to an outer block is a
                 // subtype of the region corresponding to an inner
                 // block.
-                let lub = region_rels.region_maps.nearest_common_ancestor(a_id, b_id);
+                let lub = region_rels.region_scope_tree.nearest_common_ancestor(a_id, b_id);
                 self.tcx.mk_region(ReScope(lub))
             }
 
diff --git a/src/librustc/lib.rs b/src/librustc/lib.rs
index 152b2e2aa5ebc..82f01c36fee7f 100644
--- a/src/librustc/lib.rs
+++ b/src/librustc/lib.rs
@@ -24,7 +24,6 @@
 #![feature(conservative_impl_trait)]
 #![feature(const_fn)]
 #![feature(core_intrinsics)]
-#![feature(discriminant_value)]
 #![feature(i128_type)]
 #![cfg_attr(windows, feature(libc))]
 #![feature(never_type)]
@@ -34,7 +33,6 @@
 #![feature(slice_patterns)]
 #![feature(specialization)]
 #![feature(unboxed_closures)]
-#![feature(discriminant_value)]
 #![feature(trace_macros)]
 #![feature(test)]
 
diff --git a/src/librustc/lint/builtin.rs b/src/librustc/lint/builtin.rs
index 811bf9776101d..21852468146f4 100644
--- a/src/librustc/lint/builtin.rs
+++ b/src/librustc/lint/builtin.rs
@@ -216,6 +216,12 @@ declare_lint! {
     "detects use of deprecated items"
 }
 
+declare_lint! {
+    pub UNUSED_UNSAFE,
+    Warn,
+    "unnecessary use of an `unsafe` block"
+}
+
 /// Does nothing as a lint pass, but registers some `Lint`s
 /// which are used by other parts of the compiler.
 #[derive(Copy, Clone)]
@@ -256,7 +262,8 @@ impl LintPass for HardwiredLints {
             MISSING_FRAGMENT_SPECIFIER,
             PARENTHESIZED_PARAMS_IN_TYPES_AND_MODULES,
             LATE_BOUND_LIFETIME_ARGUMENTS,
-            DEPRECATED
+            DEPRECATED,
+            UNUSED_UNSAFE
         )
     }
 }
diff --git a/src/librustc/lint/levels.rs b/src/librustc/lint/levels.rs
index ab086e5b8e90e..c5863b5618feb 100644
--- a/src/librustc/lint/levels.rs
+++ b/src/librustc/lint/levels.rs
@@ -247,13 +247,27 @@ impl<'a> LintLevelsBuilder<'a> {
                                                                     self.cur,
                                                                     Some(&specs));
                         let msg = format!("unknown lint: `{}`", name);
-                        lint::struct_lint_level(self.sess,
+                        let mut db = lint::struct_lint_level(self.sess,
                                                 lint,
                                                 level,
                                                 src,
                                                 Some(li.span.into()),
-                                                &msg)
-                            .emit();
+                                                &msg);
+                        if name.as_str().chars().any(|c| c.is_uppercase()) {
+                            let name_lower = name.as_str().to_lowercase();
+                            if let CheckLintNameResult::NoLint =
+                                    store.check_lint_name(&name_lower) {
+                                db.emit();
+                            } else {
+                                db.span_suggestion(
+                                    li.span,
+                                    "lowercase the lint name",
+                                    name_lower
+                                ).emit();
+                            }
+                        } else {
+                            db.emit();
+                        }
                     }
                 }
             }
diff --git a/src/librustc/middle/dataflow.rs b/src/librustc/middle/dataflow.rs
index d394c0f0c8734..e88678dea1d74 100644
--- a/src/librustc/middle/dataflow.rs
+++ b/src/librustc/middle/dataflow.rs
@@ -20,12 +20,11 @@ use ty::TyCtxt;
 use std::io;
 use std::mem;
 use std::usize;
-use syntax::ast;
 use syntax::print::pprust::PrintState;
 
 use rustc_data_structures::graph::OUTGOING;
 
-use util::nodemap::NodeMap;
+use util::nodemap::FxHashMap;
 use hir;
 use hir::intravisit::{self, IdRange};
 use hir::print as pprust;
@@ -56,7 +55,7 @@ pub struct DataFlowContext<'a, 'tcx: 'a, O> {
 
     // mapping from node to cfg node index
     // FIXME (#6298): Shouldn't this go with CFG?
-    nodeid_to_index: NodeMap<Vec<CFGIndex>>,
+    local_id_to_index: FxHashMap<hir::ItemLocalId, Vec<CFGIndex>>,
 
     // Bit sets per cfg node.  The following three fields (`gens`, `kills`,
     // and `on_entry`) all have the same structure. For each id in
@@ -97,15 +96,16 @@ struct PropagationContext<'a, 'b: 'a, 'tcx: 'b, O: 'a> {
     changed: bool
 }
 
-fn get_cfg_indices<'a>(id: ast::NodeId, index: &'a NodeMap<Vec<CFGIndex>>) -> &'a [CFGIndex] {
-    let opt_indices = index.get(&id);
-    opt_indices.map(|v| &v[..]).unwrap_or(&[])
+fn get_cfg_indices<'a>(id: hir::ItemLocalId,
+                       index: &'a FxHashMap<hir::ItemLocalId, Vec<CFGIndex>>)
+                       -> &'a [CFGIndex] {
+    index.get(&id).map_or(&[], |v| &v[..])
 }
 
 impl<'a, 'tcx, O:DataFlowOperator> DataFlowContext<'a, 'tcx, O> {
-    fn has_bitset_for_nodeid(&self, n: ast::NodeId) -> bool {
-        assert!(n != ast::DUMMY_NODE_ID);
-        self.nodeid_to_index.contains_key(&n)
+    fn has_bitset_for_local_id(&self, n: hir::ItemLocalId) -> bool {
+        assert!(n != hir::DUMMY_ITEM_LOCAL_ID);
+        self.local_id_to_index.contains_key(&n)
     }
 }
 
@@ -117,19 +117,20 @@ impl<'a, 'tcx, O:DataFlowOperator> pprust::PpAnn for DataFlowContext<'a, 'tcx, O
            ps: &mut pprust::State,
            node: pprust::AnnNode) -> io::Result<()> {
         let id = match node {
-            pprust::NodeName(_) => ast::CRATE_NODE_ID,
-            pprust::NodeExpr(expr) => expr.id,
-            pprust::NodeBlock(blk) => blk.id,
-            pprust::NodeItem(_) | pprust::NodeSubItem(_) => ast::CRATE_NODE_ID,
-            pprust::NodePat(pat) => pat.id
+            pprust::NodeName(_) => return Ok(()),
+            pprust::NodeExpr(expr) => expr.hir_id.local_id,
+            pprust::NodeBlock(blk) => blk.hir_id.local_id,
+            pprust::NodeItem(_) |
+            pprust::NodeSubItem(_) => return Ok(()),
+            pprust::NodePat(pat) => pat.hir_id.local_id
         };
 
-        if !self.has_bitset_for_nodeid(id) {
+        if !self.has_bitset_for_local_id(id) {
             return Ok(());
         }
 
         assert!(self.bits_per_id > 0);
-        let indices = get_cfg_indices(id, &self.nodeid_to_index);
+        let indices = get_cfg_indices(id, &self.local_id_to_index);
         for &cfgidx in indices {
             let (start, end) = self.compute_id_range(cfgidx);
             let on_entry = &self.on_entry[start.. end];
@@ -157,7 +158,7 @@ impl<'a, 'tcx, O:DataFlowOperator> pprust::PpAnn for DataFlowContext<'a, 'tcx, O
             };
 
             ps.synth_comment(
-                format!("id {}: {}{}{}{}", id, entry_str,
+                format!("id {}: {}{}{}{}", id.as_usize(), entry_str,
                         gens_str, action_kills_str, scope_kills_str))?;
             ps.s.space()?;
         }
@@ -165,9 +166,10 @@ impl<'a, 'tcx, O:DataFlowOperator> pprust::PpAnn for DataFlowContext<'a, 'tcx, O
     }
 }
 
-fn build_nodeid_to_index(body: Option<&hir::Body>,
-                         cfg: &cfg::CFG) -> NodeMap<Vec<CFGIndex>> {
-    let mut index = NodeMap();
+fn build_local_id_to_index(body: Option<&hir::Body>,
+                           cfg: &cfg::CFG)
+                           -> FxHashMap<hir::ItemLocalId, Vec<CFGIndex>> {
+    let mut index = FxHashMap();
 
     // FIXME (#6298): Would it be better to fold formals from decl
     // into cfg itself?  i.e. introduce a fn-based flow-graph in
@@ -188,14 +190,14 @@ fn build_nodeid_to_index(body: Option<&hir::Body>,
 
     /// Add mappings from the ast nodes for the formal bindings to
     /// the entry-node in the graph.
-    fn add_entries_from_fn_body(index: &mut NodeMap<Vec<CFGIndex>>,
+    fn add_entries_from_fn_body(index: &mut FxHashMap<hir::ItemLocalId, Vec<CFGIndex>>,
                                 body: &hir::Body,
                                 entry: CFGIndex) {
         use hir::intravisit::Visitor;
 
         struct Formals<'a> {
             entry: CFGIndex,
-            index: &'a mut NodeMap<Vec<CFGIndex>>,
+            index: &'a mut FxHashMap<hir::ItemLocalId, Vec<CFGIndex>>,
         }
         let mut formals = Formals { entry: entry, index: index };
         for arg in &body.arguments {
@@ -207,7 +209,7 @@ fn build_nodeid_to_index(body: Option<&hir::Body>,
             }
 
             fn visit_pat(&mut self, p: &hir::Pat) {
-                self.index.entry(p.id).or_insert(vec![]).push(self.entry);
+                self.index.entry(p.hir_id.local_id).or_insert(vec![]).push(self.entry);
                 intravisit::walk_pat(self, p)
             }
         }
@@ -259,13 +261,13 @@ impl<'a, 'tcx, O:DataFlowOperator> DataFlowContext<'a, 'tcx, O> {
         let kills2 = zeroes;
         let on_entry = vec![entry; num_nodes * words_per_id];
 
-        let nodeid_to_index = build_nodeid_to_index(body, cfg);
+        let local_id_to_index = build_local_id_to_index(body, cfg);
 
         DataFlowContext {
             tcx,
             analysis_name,
             words_per_id,
-            nodeid_to_index,
+            local_id_to_index,
             bits_per_id,
             oper,
             gens,
@@ -275,14 +277,14 @@ impl<'a, 'tcx, O:DataFlowOperator> DataFlowContext<'a, 'tcx, O> {
         }
     }
 
-    pub fn add_gen(&mut self, id: ast::NodeId, bit: usize) {
+    pub fn add_gen(&mut self, id: hir::ItemLocalId, bit: usize) {
         //! Indicates that `id` generates `bit`
-        debug!("{} add_gen(id={}, bit={})",
+        debug!("{} add_gen(id={:?}, bit={})",
                self.analysis_name, id, bit);
-        assert!(self.nodeid_to_index.contains_key(&id));
+        assert!(self.local_id_to_index.contains_key(&id));
         assert!(self.bits_per_id > 0);
 
-        let indices = get_cfg_indices(id, &self.nodeid_to_index);
+        let indices = get_cfg_indices(id, &self.local_id_to_index);
         for &cfgidx in indices {
             let (start, end) = self.compute_id_range(cfgidx);
             let gens = &mut self.gens[start.. end];
@@ -290,14 +292,14 @@ impl<'a, 'tcx, O:DataFlowOperator> DataFlowContext<'a, 'tcx, O> {
         }
     }
 
-    pub fn add_kill(&mut self, kind: KillFrom, id: ast::NodeId, bit: usize) {
+    pub fn add_kill(&mut self, kind: KillFrom, id: hir::ItemLocalId, bit: usize) {
         //! Indicates that `id` kills `bit`
-        debug!("{} add_kill(id={}, bit={})",
+        debug!("{} add_kill(id={:?}, bit={})",
                self.analysis_name, id, bit);
-        assert!(self.nodeid_to_index.contains_key(&id));
+        assert!(self.local_id_to_index.contains_key(&id));
         assert!(self.bits_per_id > 0);
 
-        let indices = get_cfg_indices(id, &self.nodeid_to_index);
+        let indices = get_cfg_indices(id, &self.local_id_to_index);
         for &cfgidx in indices {
             let (start, end) = self.compute_id_range(cfgidx);
             let kills = match kind {
@@ -341,15 +343,15 @@ impl<'a, 'tcx, O:DataFlowOperator> DataFlowContext<'a, 'tcx, O> {
     }
 
 
-    pub fn each_bit_on_entry<F>(&self, id: ast::NodeId, mut f: F) -> bool where
+    pub fn each_bit_on_entry<F>(&self, id: hir::ItemLocalId, mut f: F) -> bool where
         F: FnMut(usize) -> bool,
     {
         //! Iterates through each bit that is set on entry to `id`.
         //! Only useful after `propagate()` has been called.
-        if !self.has_bitset_for_nodeid(id) {
+        if !self.has_bitset_for_local_id(id) {
             return true;
         }
-        let indices = get_cfg_indices(id, &self.nodeid_to_index);
+        let indices = get_cfg_indices(id, &self.local_id_to_index);
         for &cfgidx in indices {
             if !self.each_bit_for_node(EntryOrExit::Entry, cfgidx, |i| f(i)) {
                 return false;
@@ -387,11 +389,11 @@ impl<'a, 'tcx, O:DataFlowOperator> DataFlowContext<'a, 'tcx, O> {
         self.each_bit(slice, f)
     }
 
-    pub fn each_gen_bit<F>(&self, id: ast::NodeId, mut f: F) -> bool where
+    pub fn each_gen_bit<F>(&self, id: hir::ItemLocalId, mut f: F) -> bool where
         F: FnMut(usize) -> bool,
     {
         //! Iterates through each bit in the gen set for `id`.
-        if !self.has_bitset_for_nodeid(id) {
+        if !self.has_bitset_for_local_id(id) {
             return true;
         }
 
@@ -401,11 +403,11 @@ impl<'a, 'tcx, O:DataFlowOperator> DataFlowContext<'a, 'tcx, O> {
             return true;
         }
 
-        let indices = get_cfg_indices(id, &self.nodeid_to_index);
+        let indices = get_cfg_indices(id, &self.local_id_to_index);
         for &cfgidx in indices {
             let (start, end) = self.compute_id_range(cfgidx);
             let gens = &self.gens[start.. end];
-            debug!("{} each_gen_bit(id={}, gens={})",
+            debug!("{} each_gen_bit(id={:?}, gens={})",
                    self.analysis_name, id, bits_to_string(gens));
             if !self.each_bit(gens, |i| f(i)) {
                 return false;
@@ -472,17 +474,17 @@ impl<'a, 'tcx, O:DataFlowOperator> DataFlowContext<'a, 'tcx, O> {
             let mut orig_kills = self.scope_kills[start.. end].to_vec();
 
             let mut changed = false;
-            for &node_id in &edge.data.exiting_scopes {
-                let opt_cfg_idx = self.nodeid_to_index.get(&node_id);
+            for &id in &edge.data.exiting_scopes {
+                let opt_cfg_idx = self.local_id_to_index.get(&id);
                 match opt_cfg_idx {
                     Some(indices) => {
                         for &cfg_idx in indices {
                             let (start, end) = self.compute_id_range(cfg_idx);
                             let kills = &self.scope_kills[start.. end];
                             if bitwise(&mut orig_kills, kills, &Union) {
-                                debug!("scope exits: scope id={} \
+                                debug!("scope exits: scope id={:?} \
                                         (node={:?} of {:?}) added killset: {}",
-                                       node_id, cfg_idx, indices,
+                                       id, cfg_idx, indices,
                                        bits_to_string(kills));
                                 changed = true;
                             }
@@ -490,8 +492,8 @@ impl<'a, 'tcx, O:DataFlowOperator> DataFlowContext<'a, 'tcx, O> {
                     }
                     None => {
                         debug!("{} add_kills_from_flow_exits flow_exit={:?} \
-                                no cfg_idx for exiting_scope={}",
-                               self.analysis_name, flow_exit, node_id);
+                                no cfg_idx for exiting_scope={:?}",
+                               self.analysis_name, flow_exit, id);
                     }
                 }
             }
@@ -559,7 +561,7 @@ impl<'a, 'b, 'tcx, O:DataFlowOperator> PropagationContext<'a, 'b, 'tcx, O> {
         // Iterate over nodes in reverse postorder
         for &node_index in nodes_po.iter().rev() {
             let node = cfg.graph.node(node_index);
-            debug!("DataFlowContext::walk_cfg idx={:?} id={} begin in_out={}",
+            debug!("DataFlowContext::walk_cfg idx={:?} id={:?} begin in_out={}",
                    node_index, node.data.id(), bits_to_string(in_out));
 
             let (start, end) = self.dfcx.compute_id_range(node_index);
diff --git a/src/librustc/middle/effect.rs b/src/librustc/middle/effect.rs
index 98934d6070328..7290353e48b0c 100644
--- a/src/librustc/middle/effect.rs
+++ b/src/librustc/middle/effect.rs
@@ -14,12 +14,14 @@ use self::RootUnsafeContext::*;
 
 use ty::{self, TyCtxt};
 use lint;
+use lint::builtin::UNUSED_UNSAFE;
 
-use syntax::ast;
-use syntax_pos::Span;
-use hir::{self, PatKind};
 use hir::def::Def;
 use hir::intravisit::{self, FnKind, Visitor, NestedVisitorMap};
+use hir::{self, PatKind};
+use syntax::ast;
+use syntax_pos::Span;
+use util::nodemap::FxHashSet;
 
 #[derive(Copy, Clone)]
 struct UnsafeContext {
@@ -47,6 +49,7 @@ struct EffectCheckVisitor<'a, 'tcx: 'a> {
 
     /// Whether we're in an unsafe context.
     unsafe_context: UnsafeContext,
+    used_unsafe: FxHashSet<ast::NodeId>,
 }
 
 impl<'a, 'tcx> EffectCheckVisitor<'a, 'tcx> {
@@ -73,7 +76,7 @@ impl<'a, 'tcx> EffectCheckVisitor<'a, 'tcx> {
             UnsafeBlock(block_id) => {
                 // OK, but record this.
                 debug!("effect: recording unsafe block as used: {}", block_id);
-                self.tcx.used_unsafe.borrow_mut().insert(block_id);
+                self.used_unsafe.insert(block_id);
             }
             UnsafeFn => {}
         }
@@ -159,7 +162,48 @@ impl<'a, 'tcx> Visitor<'tcx> for EffectCheckVisitor<'a, 'tcx> {
 
         intravisit::walk_block(self, block);
 
-        self.unsafe_context = old_unsafe_context
+        self.unsafe_context = old_unsafe_context;
+
+        // Don't warn about generated blocks, that'll just pollute the output.
+        match block.rules {
+            hir::UnsafeBlock(hir::UserProvided) => {}
+            _ => return,
+        }
+        if self.used_unsafe.contains(&block.id) {
+            return
+        }
+
+        /// Return the NodeId for an enclosing scope that is also `unsafe`
+        fn is_enclosed(tcx: TyCtxt,
+                       used_unsafe: &FxHashSet<ast::NodeId>,
+                       id: ast::NodeId) -> Option<(String, ast::NodeId)> {
+            let parent_id = tcx.hir.get_parent_node(id);
+            if parent_id != id {
+                if used_unsafe.contains(&parent_id) {
+                    Some(("block".to_string(), parent_id))
+                } else if let Some(hir::map::NodeItem(&hir::Item {
+                    node: hir::ItemFn(_, hir::Unsafety::Unsafe, _, _, _, _),
+                    ..
+                })) = tcx.hir.find(parent_id) {
+                    Some(("fn".to_string(), parent_id))
+                } else {
+                    is_enclosed(tcx, used_unsafe, parent_id)
+                }
+            } else {
+                None
+            }
+        }
+
+        let mut db = self.tcx.struct_span_lint_node(UNUSED_UNSAFE,
+                                                    block.id,
+                                                    block.span,
+                                                    "unnecessary `unsafe` block");
+        db.span_label(block.span, "unnecessary `unsafe` block");
+        if let Some((kind, id)) = is_enclosed(self.tcx, &self.used_unsafe, block.id) {
+            db.span_note(self.tcx.hir.span(id),
+                         &format!("because it's nested under this `unsafe` {}", kind));
+        }
+        db.emit();
     }
 
     fn visit_expr(&mut self, expr: &'tcx hir::Expr) {
@@ -265,6 +309,7 @@ pub fn check_crate<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) {
         tables: &ty::TypeckTables::empty(None),
         body_id: hir::BodyId { node_id: ast::CRATE_NODE_ID },
         unsafe_context: UnsafeContext::new(SafeContext),
+        used_unsafe: FxHashSet(),
     };
 
     tcx.hir.krate().visit_all_item_likes(&mut visitor.as_deep_visitor());
diff --git a/src/librustc/middle/expr_use_visitor.rs b/src/librustc/middle/expr_use_visitor.rs
index 324f9a6e9061f..374b02125a1d0 100644
--- a/src/librustc/middle/expr_use_visitor.rs
+++ b/src/librustc/middle/expr_use_visitor.rs
@@ -23,7 +23,7 @@ use hir::def::Def;
 use hir::def_id::{DefId};
 use infer::InferCtxt;
 use middle::mem_categorization as mc;
-use middle::region::RegionMaps;
+use middle::region;
 use ty::{self, TyCtxt, adjustment};
 
 use hir::{self, PatKind};
@@ -265,12 +265,12 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx, 'tcx> {
     pub fn new(delegate: &'a mut (Delegate<'tcx>+'a),
                tcx: TyCtxt<'a, 'tcx, 'tcx>,
                param_env: ty::ParamEnv<'tcx>,
-               region_maps: &'a RegionMaps,
+               region_scope_tree: &'a region::ScopeTree,
                tables: &'a ty::TypeckTables<'tcx>)
                -> Self
     {
         ExprUseVisitor {
-            mc: mc::MemCategorizationContext::new(tcx, region_maps, tables),
+            mc: mc::MemCategorizationContext::new(tcx, region_scope_tree, tables),
             delegate,
             param_env,
         }
@@ -281,12 +281,12 @@ impl<'a, 'gcx, 'tcx> ExprUseVisitor<'a, 'gcx, 'tcx> {
     pub fn with_infer(delegate: &'a mut (Delegate<'tcx>+'a),
                       infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
                       param_env: ty::ParamEnv<'tcx>,
-                      region_maps: &'a RegionMaps,
+                      region_scope_tree: &'a region::ScopeTree,
                       tables: &'a ty::TypeckTables<'tcx>)
                       -> Self
     {
         ExprUseVisitor {
-            mc: mc::MemCategorizationContext::with_infer(infcx, region_maps, tables),
+            mc: mc::MemCategorizationContext::with_infer(infcx, region_scope_tree, tables),
             delegate,
             param_env,
         }
@@ -298,7 +298,8 @@ impl<'a, 'gcx, 'tcx> ExprUseVisitor<'a, 'gcx, 'tcx> {
         for arg in &body.arguments {
             let arg_ty = return_if_err!(self.mc.node_ty(arg.pat.hir_id));
 
-            let fn_body_scope_r = self.tcx().node_scope_region(body.value.id);
+            let fn_body_scope_r =
+                self.tcx().mk_region(ty::ReScope(region::Scope::Node(body.value.hir_id.local_id)));
             let arg_cmt = self.mc.cat_rvalue(
                 arg.id,
                 arg.pat.span,
@@ -517,13 +518,17 @@ impl<'a, 'gcx, 'tcx> ExprUseVisitor<'a, 'gcx, 'tcx> {
                 self.consume_expr(&base);
             }
 
-            hir::ExprClosure(.., fn_decl_span) => {
+            hir::ExprClosure(.., fn_decl_span, _) => {
                 self.walk_captures(expr, fn_decl_span)
             }
 
             hir::ExprBox(ref base) => {
                 self.consume_expr(&base);
             }
+
+            hir::ExprYield(ref value) => {
+                self.consume_expr(&value);
+            }
         }
     }
 
@@ -538,16 +543,17 @@ impl<'a, 'gcx, 'tcx> ExprUseVisitor<'a, 'gcx, 'tcx> {
             ty::TyError => { }
             _ => {
                 let def_id = self.mc.tables.type_dependent_defs()[call.hir_id].def_id();
+                let call_scope = region::Scope::Node(call.hir_id.local_id);
                 match OverloadedCallType::from_method_id(self.tcx(), def_id) {
                     FnMutOverloadedCall => {
-                        let call_scope_r = self.tcx().node_scope_region(call.id);
+                        let call_scope_r = self.tcx().mk_region(ty::ReScope(call_scope));
                         self.borrow_expr(callee,
                                          call_scope_r,
                                          ty::MutBorrow,
                                          ClosureInvocation);
                     }
                     FnOverloadedCall => {
-                        let call_scope_r = self.tcx().node_scope_region(call.id);
+                        let call_scope_r = self.tcx().mk_region(ty::ReScope(call_scope));
                         self.borrow_expr(callee,
                                          call_scope_r,
                                          ty::ImmBorrow,
@@ -745,7 +751,8 @@ impl<'a, 'gcx, 'tcx> ExprUseVisitor<'a, 'gcx, 'tcx> {
                 // Converting from a &T to *T (or &mut T to *mut T) is
                 // treated as borrowing it for the enclosing temporary
                 // scope.
-                let r = self.tcx().node_scope_region(expr.id);
+                let r = self.tcx().mk_region(ty::ReScope(
+                    region::Scope::Node(expr.hir_id.local_id)));
 
                 self.delegate.borrow(expr.id,
                                      expr.span,
diff --git a/src/librustc/middle/free_region.rs b/src/librustc/middle/free_region.rs
index de738fba30e92..d4cee25bb8fa2 100644
--- a/src/librustc/middle/free_region.rs
+++ b/src/librustc/middle/free_region.rs
@@ -16,11 +16,11 @@
 //! region outlives another and so forth.
 
 use hir::def_id::DefId;
-use middle::region::RegionMaps;
+use middle::region;
 use ty::{self, Lift, TyCtxt, Region};
 use rustc_data_structures::transitive_relation::TransitiveRelation;
 
-/// Combines a `RegionMaps` (which governs relationships between
+/// Combines a `region::ScopeTree` (which governs relationships between
 /// scopes) and a `FreeRegionMap` (which governs relationships between
 /// free regions) to yield a complete relation between concrete
 /// regions.
@@ -34,7 +34,7 @@ pub struct RegionRelations<'a, 'gcx: 'tcx, 'tcx: 'a> {
     pub context: DefId,
 
     /// region maps for the given context
-    pub region_maps: &'a RegionMaps,
+    pub region_scope_tree: &'a region::ScopeTree,
 
     /// free-region relationships
     pub free_regions: &'a FreeRegionMap<'tcx>,
@@ -44,13 +44,13 @@ impl<'a, 'gcx, 'tcx> RegionRelations<'a, 'gcx, 'tcx> {
     pub fn new(
         tcx: TyCtxt<'a, 'gcx, 'tcx>,
         context: DefId,
-        region_maps: &'a RegionMaps,
+        region_scope_tree: &'a region::ScopeTree,
         free_regions: &'a FreeRegionMap<'tcx>,
     ) -> Self {
         Self {
             tcx,
             context,
-            region_maps,
+            region_scope_tree,
             free_regions,
         }
     }
@@ -68,16 +68,16 @@ impl<'a, 'gcx, 'tcx> RegionRelations<'a, 'gcx, 'tcx> {
                     true,
 
                 (&ty::ReScope(sub_scope), &ty::ReScope(super_scope)) =>
-                    self.region_maps.is_subscope_of(sub_scope, super_scope),
+                    self.region_scope_tree.is_subscope_of(sub_scope, super_scope),
 
                 (&ty::ReScope(sub_scope), &ty::ReEarlyBound(ref br)) => {
-                    let fr_scope = self.region_maps.early_free_extent(self.tcx, br);
-                    self.region_maps.is_subscope_of(sub_scope, fr_scope)
+                    let fr_scope = self.region_scope_tree.early_free_scope(self.tcx, br);
+                    self.region_scope_tree.is_subscope_of(sub_scope, fr_scope)
                 }
 
                 (&ty::ReScope(sub_scope), &ty::ReFree(ref fr)) => {
-                    let fr_scope = self.region_maps.free_extent(self.tcx, fr);
-                    self.region_maps.is_subscope_of(sub_scope, fr_scope)
+                    let fr_scope = self.region_scope_tree.free_scope(self.tcx, fr);
+                    self.region_scope_tree.is_subscope_of(sub_scope, fr_scope)
                 }
 
                 (&ty::ReEarlyBound(_), &ty::ReEarlyBound(_)) |
diff --git a/src/librustc/middle/lang_items.rs b/src/librustc/middle/lang_items.rs
index 9ba4252b52e57..ae3e3a30f371e 100644
--- a/src/librustc/middle/lang_items.rs
+++ b/src/librustc/middle/lang_items.rs
@@ -316,6 +316,9 @@ language_item_table! {
     FnMutTraitLangItem,              "fn_mut",                  fn_mut_trait;
     FnOnceTraitLangItem,             "fn_once",                 fn_once_trait;
 
+    GeneratorStateLangItem,          "generator_state",         gen_state;
+    GeneratorTraitLangItem,          "generator",               gen_trait;
+
     EqTraitLangItem,                 "eq",                      eq_trait;
     OrdTraitLangItem,                "ord",                     ord_trait;
 
diff --git a/src/librustc/middle/liveness.rs b/src/librustc/middle/liveness.rs
index 8e5f748c78e29..6910a21ca5526 100644
--- a/src/librustc/middle/liveness.rs
+++ b/src/librustc/middle/liveness.rs
@@ -460,7 +460,7 @@ fn visit_expr<'a, 'tcx>(ir: &mut IrMaps<'a, 'tcx>, expr: &'tcx Expr) {
       hir::ExprAgain(_) | hir::ExprLit(_) | hir::ExprRet(..) |
       hir::ExprBlock(..) | hir::ExprAssign(..) | hir::ExprAssignOp(..) |
       hir::ExprStruct(..) | hir::ExprRepeat(..) |
-      hir::ExprInlineAsm(..) | hir::ExprBox(..) |
+      hir::ExprInlineAsm(..) | hir::ExprBox(..) | hir::ExprYield(..) |
       hir::ExprType(..) | hir::ExprPath(hir::QPath::TypeRelative(..)) => {
           intravisit::walk_expr(ir, expr);
       }
@@ -881,7 +881,6 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
 
         match expr.node {
           // Interesting cases with control flow or which gen/kill
-
           hir::ExprPath(hir::QPath::Resolved(_, ref path)) => {
               self.access_path(expr.id, path, succ, ACC_READ | ACC_USE)
           }
@@ -894,7 +893,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
               self.propagate_through_expr(&e, succ)
           }
 
-          hir::ExprClosure(.., blk_id, _) => {
+          hir::ExprClosure(.., blk_id, _, _) => {
               debug!("{} is an ExprClosure", self.ir.tcx.hir.node_to_pretty_string(expr.id));
 
               /*
@@ -1116,6 +1115,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
           hir::ExprCast(ref e, _) |
           hir::ExprType(ref e, _) |
           hir::ExprUnary(_, ref e) |
+          hir::ExprYield(ref e) |
           hir::ExprRepeat(ref e, _) => {
             self.propagate_through_expr(&e, succ)
           }
@@ -1224,18 +1224,23 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
         }
     }
 
+    fn access_var(&mut self, id: NodeId, nid: NodeId, succ: LiveNode, acc: u32, span: Span)
+                  -> LiveNode {
+        let ln = self.live_node(id, span);
+        if acc != 0 {
+            self.init_from_succ(ln, succ);
+            let var = self.variable(nid, span);
+            self.acc(ln, var, acc);
+        }
+        ln
+    }
+
     fn access_path(&mut self, id: NodeId, path: &hir::Path, succ: LiveNode, acc: u32)
                    -> LiveNode {
         match path.def {
           Def::Local(def_id) => {
             let nid = self.ir.tcx.hir.as_local_node_id(def_id).unwrap();
-            let ln = self.live_node(id, path.span);
-            if acc != 0 {
-                self.init_from_succ(ln, succ);
-                let var = self.variable(nid, path.span);
-                self.acc(ln, var, acc);
-            }
-            ln
+            self.access_var(id, nid, succ, acc, path.span)
           }
           _ => succ
         }
@@ -1398,7 +1403,7 @@ fn check_expr<'a, 'tcx>(this: &mut Liveness<'a, 'tcx>, expr: &'tcx Expr) {
       hir::ExprBreak(..) | hir::ExprAgain(..) | hir::ExprLit(_) |
       hir::ExprBlock(..) | hir::ExprAddrOf(..) |
       hir::ExprStruct(..) | hir::ExprRepeat(..) |
-      hir::ExprClosure(..) | hir::ExprPath(_) |
+      hir::ExprClosure(..) | hir::ExprPath(_) | hir::ExprYield(..) |
       hir::ExprBox(..) | hir::ExprType(..) => {
         intravisit::walk_expr(this, expr);
       }
diff --git a/src/librustc/middle/mem_categorization.rs b/src/librustc/middle/mem_categorization.rs
index 8cd023b8e638b..0b0fbad9fc39c 100644
--- a/src/librustc/middle/mem_categorization.rs
+++ b/src/librustc/middle/mem_categorization.rs
@@ -69,7 +69,7 @@ pub use self::Note::*;
 
 use self::Aliasability::*;
 
-use middle::region::RegionMaps;
+use middle::region;
 use hir::def_id::{DefId, DefIndex};
 use hir::map as hir_map;
 use infer::InferCtxt;
@@ -283,7 +283,7 @@ impl ast_node for hir::Pat {
 #[derive(Clone)]
 pub struct MemCategorizationContext<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
     pub tcx: TyCtxt<'a, 'gcx, 'tcx>,
-    pub region_maps: &'a RegionMaps,
+    pub region_scope_tree: &'a region::ScopeTree,
     pub tables: &'a ty::TypeckTables<'tcx>,
     infcx: Option<&'a InferCtxt<'a, 'gcx, 'tcx>>,
 }
@@ -391,21 +391,21 @@ impl MutabilityCategory {
 
 impl<'a, 'tcx> MemCategorizationContext<'a, 'tcx, 'tcx> {
     pub fn new(tcx: TyCtxt<'a, 'tcx, 'tcx>,
-               region_maps: &'a RegionMaps,
+               region_scope_tree: &'a region::ScopeTree,
                tables: &'a ty::TypeckTables<'tcx>)
                -> MemCategorizationContext<'a, 'tcx, 'tcx> {
-        MemCategorizationContext { tcx, region_maps, tables, infcx: None }
+        MemCategorizationContext { tcx, region_scope_tree, tables, infcx: None }
     }
 }
 
 impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
     pub fn with_infer(infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
-                      region_maps: &'a RegionMaps,
+                      region_scope_tree: &'a region::ScopeTree,
                       tables: &'a ty::TypeckTables<'tcx>)
                       -> MemCategorizationContext<'a, 'gcx, 'tcx> {
         MemCategorizationContext {
             tcx: infcx.tcx,
-            region_maps,
+            region_scope_tree,
             tables,
             infcx: Some(infcx),
         }
@@ -625,7 +625,7 @@ impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
           hir::ExprAddrOf(..) | hir::ExprCall(..) |
           hir::ExprAssign(..) | hir::ExprAssignOp(..) |
           hir::ExprClosure(..) | hir::ExprRet(..) |
-          hir::ExprUnary(..) |
+          hir::ExprUnary(..) | hir::ExprYield(..) |
           hir::ExprMethodCall(..) | hir::ExprCast(..) |
           hir::ExprArray(..) | hir::ExprTup(..) | hir::ExprIf(..) |
           hir::ExprBinary(..) | hir::ExprWhile(..) |
@@ -725,9 +725,14 @@ impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
         // FnMut          | copied -> &'env mut  | upvar -> &'env mut -> &'up bk
         // FnOnce         | copied               | upvar -> &'up bk
 
-        let kind = match self.tables.closure_kinds().get(fn_hir_id) {
-            Some(&(kind, _)) => kind,
-            None => span_bug!(span, "missing closure kind")
+        let kind = match self.node_ty(fn_hir_id)?.sty {
+            ty::TyGenerator(..) => ty::ClosureKind::FnOnce,
+            _ => {
+                match self.tables.closure_kinds().get(fn_hir_id) {
+                    Some(&(kind, _)) => kind,
+                    None => span_bug!(span, "missing closure kind"),
+                }
+            }
         };
 
         let closure_expr_def_index = self.tcx.hir.local_def_id(fn_node_id).index;
@@ -856,9 +861,8 @@ impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
 
     /// Returns the lifetime of a temporary created by expr with id `id`.
     /// This could be `'static` if `id` is part of a constant expression.
-    pub fn temporary_scope(&self, id: ast::NodeId) -> ty::Region<'tcx>
-    {
-        let scope = self.region_maps.temporary_scope(id);
+    pub fn temporary_scope(&self, id: hir::ItemLocalId) -> ty::Region<'tcx> {
+        let scope = self.region_scope_tree.temporary_scope(id);
         self.tcx.mk_region(match scope {
             Some(scope) => ty::ReScope(scope),
             None => ty::ReStatic
@@ -885,7 +889,7 @@ impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
         let re = if promotable {
             self.tcx.types.re_static
         } else {
-            self.temporary_scope(id)
+            self.temporary_scope(self.tcx.hir.node_to_hir_id(id).local_id)
         };
         let ret = self.cat_rvalue(id, span, re, expr_ty);
         debug!("cat_rvalue_node ret {:?}", ret);
diff --git a/src/librustc/middle/reachable.rs b/src/librustc/middle/reachable.rs
index 666f71cca06bb..3efc696f2a50a 100644
--- a/src/librustc/middle/reachable.rs
+++ b/src/librustc/middle/reachable.rs
@@ -296,7 +296,7 @@ impl<'a, 'tcx> ReachableContext<'a, 'tcx> {
                     hir::ImplItemKind::Type(_) => {}
                 }
             }
-            hir_map::NodeExpr(&hir::Expr { node: hir::ExprClosure(.., body, _), .. }) => {
+            hir_map::NodeExpr(&hir::Expr { node: hir::ExprClosure(.., body, _, _), .. }) => {
                 self.visit_nested_body(body);
             }
             // Nothing to recurse on for these
diff --git a/src/librustc/middle/region.rs b/src/librustc/middle/region.rs
index 45a3080ed91ff..ae9866edc53b2 100644
--- a/src/librustc/middle/region.rs
+++ b/src/librustc/middle/region.rs
@@ -8,23 +8,21 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-//! This file actually contains two passes related to regions.  The first
-//! pass builds up the `scope_map`, which describes the parent links in
-//! the region hierarchy.  The second pass infers which types must be
-//! region parameterized.
+//! This file builds up the `ScopeTree`, which describes
+//! the parent links in the region hierarchy.
 //!
 //! Most of the documentation on regions can be found in
 //! `middle/infer/region_inference/README.md`
 
-use hir::map as hir_map;
-use util::nodemap::{FxHashMap, NodeMap, NodeSet};
+use util::nodemap::{FxHashMap, FxHashSet};
 use ty;
 
+use std::collections::hash_map::Entry;
 use std::mem;
 use std::rc::Rc;
 use syntax::codemap;
 use syntax::ast;
-use syntax_pos::Span;
+use syntax_pos::{Span, DUMMY_SP};
 use ty::TyCtxt;
 use ty::maps::Providers;
 
@@ -34,24 +32,24 @@ use hir::intravisit::{self, Visitor, NestedVisitorMap};
 use hir::{Block, Arm, Pat, PatKind, Stmt, Expr, Local};
 use mir::transform::MirSource;
 
-/// CodeExtent represents a statically-describable extent that can be
+/// Scope represents a statically-describable scope that can be
 /// used to bound the lifetime/region for values.
 ///
-/// `Misc(node_id)`: Any AST node that has any extent at all has the
-/// `Misc(node_id)` extent. Other variants represent special cases not
+/// `Node(node_id)`: Any AST node that has any scope at all has the
+/// `Node(node_id)` scope. Other variants represent special cases not
 /// immediately derivable from the abstract syntax tree structure.
 ///
-/// `DestructionScope(node_id)` represents the extent of destructors
+/// `DestructionScope(node_id)` represents the scope of destructors
 /// implicitly-attached to `node_id` that run immediately after the
 /// expression for `node_id` itself. Not every AST node carries a
 /// `DestructionScope`, but those that are `terminating_scopes` do;
-/// see discussion with `RegionMaps`.
+/// see discussion with `ScopeTree`.
 ///
 /// `Remainder(BlockRemainder { block, statement_index })` represents
-/// the extent of user code running immediately after the initializer
+/// the scope of user code running immediately after the initializer
 /// expression for the indexed statement, until the end of the block.
 ///
-/// So: the following code can be broken down into the extents beneath:
+/// So: the following code can be broken down into the scopes beneath:
 /// ```
 /// let a = f().g( 'b: { let x = d(); let y = d(); x.h(y)  }   ) ;
 /// ```
@@ -69,21 +67,21 @@ use mir::transform::MirSource;
 ///         +--+                                                      (M2.)
 /// +-----------------------------------------------------------+     (M1.)
 ///
-///  (M1.): Misc extent of the whole `let a = ...;` statement.
-///  (M2.): Misc extent of the `f()` expression.
-///  (M3.): Misc extent of the `f().g(..)` expression.
-///  (M4.): Misc extent of the block labeled `'b:`.
-///  (M5.): Misc extent of the `let x = d();` statement
+///  (M1.): Node scope of the whole `let a = ...;` statement.
+///  (M2.): Node scope of the `f()` expression.
+///  (M3.): Node scope of the `f().g(..)` expression.
+///  (M4.): Node scope of the block labeled `'b:`.
+///  (M5.): Node scope of the `let x = d();` statement
 ///  (D6.): DestructionScope for temporaries created during M5.
-///  (R7.): Remainder extent for block `'b:`, stmt 0 (let x = ...).
-///  (M8.): Misc Extent of the `let y = d();` statement.
+///  (R7.): Remainder scope for block `'b:`, stmt 0 (let x = ...).
+///  (M8.): Node scope of the `let y = d();` statement.
 ///  (D9.): DestructionScope for temporaries created during M8.
-/// (R10.): Remainder extent for block `'b:`, stmt 1 (let y = ...).
+/// (R10.): Remainder scope for block `'b:`, stmt 1 (let y = ...).
 /// (D11.): DestructionScope for temporaries and bindings from block `'b:`.
 /// (D12.): DestructionScope for temporaries created during M1 (e.g. f()).
 ///
 /// Note that while the above picture shows the destruction scopes
-/// as following their corresponding misc extents, in the internal
+/// as following their corresponding node scopes, in the internal
 /// data structures of the compiler the destruction scopes are
 /// represented as enclosing parents. This is sound because we use the
 /// enclosing parent relationship just to ensure that referenced
@@ -96,21 +94,21 @@ use mir::transform::MirSource;
 /// actually attach a more meaningful ordering to scopes than the one
 /// generated via deriving here.
 #[derive(Clone, PartialEq, PartialOrd, Eq, Ord, Hash, Debug, Copy, RustcEncodable, RustcDecodable)]
-pub enum CodeExtent {
-    Misc(ast::NodeId),
+pub enum Scope {
+    Node(hir::ItemLocalId),
 
-    // extent of the call-site for a function or closure (outlives
-    // the parameters as well as the body).
-    CallSiteScope(hir::BodyId),
+    // Scope of the call-site for a function or closure
+    // (outlives the arguments as well as the body).
+    CallSite(hir::ItemLocalId),
 
-    // extent of parameters passed to a function or closure (they
-    // outlive its body)
-    ParameterScope(hir::BodyId),
+    // Scope of arguments passed to a function or closure
+    // (they outlive its body).
+    Arguments(hir::ItemLocalId),
 
-    // extent of destructors for temporaries of node-id
-    DestructionScope(ast::NodeId),
+    // Scope of destructors for temporaries of node-id.
+    Destruction(hir::ItemLocalId),
 
-    // extent of code following a `let id = expr;` binding in a block
+    // Scope following a `let id = expr;` binding in a block.
     Remainder(BlockRemainder)
 }
 
@@ -125,95 +123,106 @@ pub enum CodeExtent {
 /// * the subscope with `first_statement_index == 0` is scope of both
 ///   `a` and `b`; it does not include EXPR_1, but does include
 ///   everything after that first `let`. (If you want a scope that
-///   includes EXPR_1 as well, then do not use `CodeExtent::Remainder`,
-///   but instead another `CodeExtent` that encompasses the whole block,
-///   e.g. `CodeExtent::Misc`.
+///   includes EXPR_1 as well, then do not use `Scope::Remainder`,
+///   but instead another `Scope` that encompasses the whole block,
+///   e.g. `Scope::Node`.
 ///
 /// * the subscope with `first_statement_index == 1` is scope of `c`,
 ///   and thus does not include EXPR_2, but covers the `...`.
 #[derive(Clone, PartialEq, PartialOrd, Eq, Ord, Hash, RustcEncodable,
          RustcDecodable, Debug, Copy)]
 pub struct BlockRemainder {
-    pub block: ast::NodeId,
+    pub block: hir::ItemLocalId,
     pub first_statement_index: u32,
 }
 
-impl CodeExtent {
-    /// Returns a node id associated with this scope.
+impl Scope {
+    /// Returns a item-local id associated with this scope.
     ///
     /// NB: likely to be replaced as API is refined; e.g. pnkfelix
     /// anticipates `fn entry_node_id` and `fn each_exit_node_id`.
-    pub fn node_id(&self) -> ast::NodeId {
+    pub fn item_local_id(&self) -> hir::ItemLocalId {
         match *self {
-            CodeExtent::Misc(node_id) => node_id,
+            Scope::Node(id) => id,
 
             // These cases all return rough approximations to the
-            // precise extent denoted by `self`.
-            CodeExtent::Remainder(br) => br.block,
-            CodeExtent::DestructionScope(node_id) => node_id,
-            CodeExtent::CallSiteScope(body_id) |
-            CodeExtent::ParameterScope(body_id) => body_id.node_id,
+            // precise scope denoted by `self`.
+            Scope::Remainder(br) => br.block,
+            Scope::Destruction(id) |
+            Scope::CallSite(id) |
+            Scope::Arguments(id) => id,
         }
     }
 
-    /// Returns the span of this CodeExtent.  Note that in general the
+    pub fn node_id(&self, tcx: TyCtxt, scope_tree: &ScopeTree) -> ast::NodeId {
+        match scope_tree.root_body {
+            Some(hir_id) => {
+                tcx.hir.hir_to_node_id(hir::HirId {
+                    owner: hir_id.owner,
+                    local_id: self.item_local_id()
+                })
+            }
+            None => ast::DUMMY_NODE_ID
+        }
+    }
+
+    /// Returns the span of this Scope.  Note that in general the
     /// returned span may not correspond to the span of any node id in
     /// the AST.
-    pub fn span(&self, hir_map: &hir_map::Map) -> Option<Span> {
-        match hir_map.find(self.node_id()) {
-            Some(hir_map::NodeBlock(ref blk)) => {
-                match *self {
-                    CodeExtent::CallSiteScope(_) |
-                    CodeExtent::ParameterScope(_) |
-                    CodeExtent::Misc(_) |
-                    CodeExtent::DestructionScope(_) => Some(blk.span),
-
-                    CodeExtent::Remainder(r) => {
-                        assert_eq!(r.block, blk.id);
-                        // Want span for extent starting after the
-                        // indexed statement and ending at end of
-                        // `blk`; reuse span of `blk` and shift `lo`
-                        // forward to end of indexed statement.
-                        //
-                        // (This is the special case aluded to in the
-                        // doc-comment for this method)
-                        let stmt_span = blk.stmts[r.first_statement_index as usize].span;
-                        Some(Span { lo: stmt_span.hi, hi: blk.span.hi, ctxt: stmt_span.ctxt })
-                    }
+    pub fn span(&self, tcx: TyCtxt, scope_tree: &ScopeTree) -> Span {
+        let node_id = self.node_id(tcx, scope_tree);
+        if node_id == ast::DUMMY_NODE_ID {
+            return DUMMY_SP;
+        }
+        let span = tcx.hir.span(node_id);
+        if let Scope::Remainder(r) = *self {
+            if let hir::map::NodeBlock(ref blk) = tcx.hir.get(node_id) {
+                // Want span for scope starting after the
+                // indexed statement and ending at end of
+                // `blk`; reuse span of `blk` and shift `lo`
+                // forward to end of indexed statement.
+                //
+                // (This is the special case aluded to in the
+                // doc-comment for this method)
+
+                let stmt_span = blk.stmts[r.first_statement_index as usize].span;
+
+                // To avoid issues with macro-generated spans, the span
+                // of the statement must be nested in that of the block.
+                if span.lo() <= stmt_span.lo() && stmt_span.lo() <= span.hi() {
+                    return Span::new(stmt_span.lo(), span.hi(), span.ctxt());
                 }
             }
-            Some(hir_map::NodeExpr(ref expr)) => Some(expr.span),
-            Some(hir_map::NodeStmt(ref stmt)) => Some(stmt.span),
-            Some(hir_map::NodeItem(ref item)) => Some(item.span),
-            Some(_) | None => None,
          }
+         span
     }
 }
 
-/// The region maps encode information about region relationships.
-pub struct RegionMaps {
+/// The region scope tree encodes information about region relationships.
+#[derive(Default)]
+pub struct ScopeTree {
     /// If not empty, this body is the root of this region hierarchy.
-    root_body: Option<hir::BodyId>,
+    root_body: Option<hir::HirId>,
 
     /// The parent of the root body owner, if the latter is an
     /// an associated const or method, as impls/traits can also
     /// have lifetime parameters free in this body.
     root_parent: Option<ast::NodeId>,
 
-    /// `scope_map` maps from a scope id to the enclosing scope id;
+    /// `parent_map` maps from a scope id to the enclosing scope id;
     /// this is usually corresponding to the lexical nesting, though
     /// in the case of closures the parent scope is the innermost
     /// conditional expression or repeating block. (Note that the
     /// enclosing scope id for the block associated with a closure is
     /// the closure itself.)
-    scope_map: FxHashMap<CodeExtent, CodeExtent>,
+    parent_map: FxHashMap<Scope, Scope>,
 
     /// `var_map` maps from a variable or binding id to the block in
     /// which that variable is declared.
-    var_map: NodeMap<CodeExtent>,
+    var_map: FxHashMap<hir::ItemLocalId, Scope>,
 
     /// maps from a node-id to the associated destruction scope (if any)
-    destruction_scopes: NodeMap<CodeExtent>,
+    destruction_scopes: FxHashMap<hir::ItemLocalId, Scope>,
 
     /// `rvalue_scopes` includes entries for those expressions whose cleanup scope is
     /// larger than the default. The map goes from the expression id
@@ -221,7 +230,9 @@ pub struct RegionMaps {
     /// table, the appropriate cleanup scope is the innermost
     /// enclosing statement, conditional expression, or repeating
     /// block (see `terminating_scopes`).
-    rvalue_scopes: NodeMap<CodeExtent>,
+    /// In constants, None is used to indicate that certain expressions
+    /// escape into 'static and should have no local cleanup scope.
+    rvalue_scopes: FxHashMap<hir::ItemLocalId, Option<Scope>>,
 
     /// Encodes the hierarchy of fn bodies. Every fn body (including
     /// closures) forms its own distinct region hierarchy, rooted in
@@ -233,7 +244,11 @@ pub struct RegionMaps {
     /// closure defined by that fn. See the "Modeling closures"
     /// section of the README in infer::region_inference for
     /// more details.
-    fn_tree: NodeMap<ast::NodeId>,
+    closure_tree: FxHashMap<hir::ItemLocalId, hir::ItemLocalId>,
+
+    /// If there are any `yield` nested within a scope, this map
+    /// stores the `Span` of the first one.
+    yield_in_scope: FxHashMap<Scope, Span>,
 }
 
 #[derive(Debug, Copy, Clone)]
@@ -244,20 +259,20 @@ pub struct Context {
     /// arranged into a tree. See the "Modeling closures" section of
     /// the README in infer::region_inference for more
     /// details.
-    root_id: Option<ast::NodeId>,
+    root_id: Option<hir::ItemLocalId>,
 
     /// the scope that contains any new variables declared
-    var_parent: Option<CodeExtent>,
+    var_parent: Option<Scope>,
 
     /// region parent of expressions etc
-    parent: Option<CodeExtent>,
+    parent: Option<Scope>,
 }
 
 struct RegionResolutionVisitor<'a, 'tcx: 'a> {
     tcx: TyCtxt<'a, 'tcx, 'tcx>,
 
-    // Generated maps:
-    region_maps: RegionMaps,
+    // Generated scope tree:
+    scope_tree: ScopeTree,
 
     cx: Context,
 
@@ -281,124 +296,117 @@ struct RegionResolutionVisitor<'a, 'tcx: 'a> {
     /// arbitrary amounts of stack space. Terminating scopes end
     /// up being contained in a DestructionScope that contains the
     /// destructor's execution.
-    terminating_scopes: NodeSet,
+    terminating_scopes: FxHashSet<hir::ItemLocalId>,
 }
 
 
-impl<'tcx> RegionMaps {
-    pub fn new() -> Self {
-        RegionMaps {
-            root_body: None,
-            root_parent: None,
-            scope_map: FxHashMap(),
-            destruction_scopes: FxHashMap(),
-            var_map: NodeMap(),
-            rvalue_scopes: NodeMap(),
-            fn_tree: NodeMap(),
-        }
-    }
-
-    pub fn record_code_extent(&mut self,
-                              child: CodeExtent,
-                              parent: Option<CodeExtent>) {
+impl<'tcx> ScopeTree {
+    pub fn record_scope_parent(&mut self, child: Scope, parent: Option<Scope>) {
         debug!("{:?}.parent = {:?}", child, parent);
 
         if let Some(p) = parent {
-            let prev = self.scope_map.insert(child, p);
+            let prev = self.parent_map.insert(child, p);
             assert!(prev.is_none());
         }
 
         // record the destruction scopes for later so we can query them
-        if let CodeExtent::DestructionScope(n) = child {
+        if let Scope::Destruction(n) = child {
             self.destruction_scopes.insert(n, child);
         }
     }
 
-    pub fn each_encl_scope<E>(&self, mut e:E) where E: FnMut(CodeExtent, CodeExtent) {
-        for (&child, &parent) in &self.scope_map {
+    pub fn each_encl_scope<E>(&self, mut e:E) where E: FnMut(Scope, Scope) {
+        for (&child, &parent) in &self.parent_map {
             e(child, parent)
         }
     }
 
-    pub fn each_var_scope<E>(&self, mut e:E) where E: FnMut(&ast::NodeId, CodeExtent) {
+    pub fn each_var_scope<E>(&self, mut e:E) where E: FnMut(&hir::ItemLocalId, Scope) {
         for (child, &parent) in self.var_map.iter() {
             e(child, parent)
         }
     }
 
-    pub fn opt_destruction_extent(&self, n: ast::NodeId) -> Option<CodeExtent> {
+    pub fn opt_destruction_scope(&self, n: hir::ItemLocalId) -> Option<Scope> {
         self.destruction_scopes.get(&n).cloned()
     }
 
-    /// Records that `sub_fn` is defined within `sup_fn`. These ids
+    /// Records that `sub_closure` is defined within `sup_closure`. These ids
     /// should be the id of the block that is the fn body, which is
     /// also the root of the region hierarchy for that fn.
-    fn record_fn_parent(&mut self, sub_fn: ast::NodeId, sup_fn: ast::NodeId) {
-        debug!("record_fn_parent(sub_fn={:?}, sup_fn={:?})", sub_fn, sup_fn);
-        assert!(sub_fn != sup_fn);
-        let previous = self.fn_tree.insert(sub_fn, sup_fn);
+    fn record_closure_parent(&mut self,
+                             sub_closure: hir::ItemLocalId,
+                             sup_closure: hir::ItemLocalId) {
+        debug!("record_closure_parent(sub_closure={:?}, sup_closure={:?})",
+               sub_closure, sup_closure);
+        assert!(sub_closure != sup_closure);
+        let previous = self.closure_tree.insert(sub_closure, sup_closure);
         assert!(previous.is_none());
     }
 
-    fn fn_is_enclosed_by(&self, mut sub_fn: ast::NodeId, sup_fn: ast::NodeId) -> bool {
+    fn closure_is_enclosed_by(&self,
+                              mut sub_closure: hir::ItemLocalId,
+                              sup_closure: hir::ItemLocalId) -> bool {
         loop {
-            if sub_fn == sup_fn { return true; }
-            match self.fn_tree.get(&sub_fn) {
-                Some(&s) => { sub_fn = s; }
+            if sub_closure == sup_closure { return true; }
+            match self.closure_tree.get(&sub_closure) {
+                Some(&s) => { sub_closure = s; }
                 None => { return false; }
             }
         }
     }
 
-    fn record_var_scope(&mut self, var: ast::NodeId, lifetime: CodeExtent) {
+    fn record_var_scope(&mut self, var: hir::ItemLocalId, lifetime: Scope) {
         debug!("record_var_scope(sub={:?}, sup={:?})", var, lifetime);
-        assert!(var != lifetime.node_id());
+        assert!(var != lifetime.item_local_id());
         self.var_map.insert(var, lifetime);
     }
 
-    fn record_rvalue_scope(&mut self, var: ast::NodeId, lifetime: CodeExtent) {
+    fn record_rvalue_scope(&mut self, var: hir::ItemLocalId, lifetime: Option<Scope>) {
         debug!("record_rvalue_scope(sub={:?}, sup={:?})", var, lifetime);
-        assert!(var != lifetime.node_id());
+        if let Some(lifetime) = lifetime {
+            assert!(var != lifetime.item_local_id());
+        }
         self.rvalue_scopes.insert(var, lifetime);
     }
 
-    pub fn opt_encl_scope(&self, id: CodeExtent) -> Option<CodeExtent> {
+    pub fn opt_encl_scope(&self, id: Scope) -> Option<Scope> {
         //! Returns the narrowest scope that encloses `id`, if any.
-        self.scope_map.get(&id).cloned()
+        self.parent_map.get(&id).cloned()
     }
 
     #[allow(dead_code)] // used in cfg
-    pub fn encl_scope(&self, id: CodeExtent) -> CodeExtent {
+    pub fn encl_scope(&self, id: Scope) -> Scope {
         //! Returns the narrowest scope that encloses `id`, if any.
         self.opt_encl_scope(id).unwrap()
     }
 
     /// Returns the lifetime of the local variable `var_id`
-    pub fn var_scope(&self, var_id: ast::NodeId) -> CodeExtent {
+    pub fn var_scope(&self, var_id: hir::ItemLocalId) -> Scope {
         match self.var_map.get(&var_id) {
             Some(&r) => r,
             None => { bug!("no enclosing scope for id {:?}", var_id); }
         }
     }
 
-    pub fn temporary_scope(&self, expr_id: ast::NodeId) -> Option<CodeExtent> {
+    pub fn temporary_scope(&self, expr_id: hir::ItemLocalId) -> Option<Scope> {
         //! Returns the scope when temp created by expr_id will be cleaned up
 
         // check for a designated rvalue scope
         if let Some(&s) = self.rvalue_scopes.get(&expr_id) {
             debug!("temporary_scope({:?}) = {:?} [custom]", expr_id, s);
-            return Some(s);
+            return s;
         }
 
         // else, locate the innermost terminating scope
         // if there's one. Static items, for instance, won't
         // have an enclosing scope, hence no scope will be
         // returned.
-        let mut id = CodeExtent::Misc(expr_id);
+        let mut id = Scope::Node(expr_id);
 
-        while let Some(&p) = self.scope_map.get(&id) {
+        while let Some(&p) = self.parent_map.get(&id) {
             match p {
-                CodeExtent::DestructionScope(..) => {
+                Scope::Destruction(..) => {
                     debug!("temporary_scope({:?}) = {:?} [enclosing]",
                            expr_id, id);
                     return Some(id);
@@ -411,7 +419,7 @@ impl<'tcx> RegionMaps {
         return None;
     }
 
-    pub fn var_region(&self, id: ast::NodeId) -> ty::RegionKind {
+    pub fn var_region(&self, id: hir::ItemLocalId) -> ty::RegionKind {
         //! Returns the lifetime of the variable `id`.
 
         let scope = ty::ReScope(self.var_scope(id));
@@ -419,7 +427,7 @@ impl<'tcx> RegionMaps {
         scope
     }
 
-    pub fn scopes_intersect(&self, scope1: CodeExtent, scope2: CodeExtent)
+    pub fn scopes_intersect(&self, scope1: Scope, scope2: Scope)
                             -> bool {
         self.is_subscope_of(scope1, scope2) ||
         self.is_subscope_of(scope2, scope1)
@@ -428,8 +436,8 @@ impl<'tcx> RegionMaps {
     /// Returns true if `subscope` is equal to or is lexically nested inside `superscope` and false
     /// otherwise.
     pub fn is_subscope_of(&self,
-                          subscope: CodeExtent,
-                          superscope: CodeExtent)
+                          subscope: Scope,
+                          superscope: Scope)
                           -> bool {
         let mut s = subscope;
         debug!("is_subscope_of({:?}, {:?})", subscope, superscope);
@@ -453,22 +461,22 @@ impl<'tcx> RegionMaps {
     /// Finds the nearest common ancestor (if any) of two scopes.  That is, finds the smallest
     /// scope which is greater than or equal to both `scope_a` and `scope_b`.
     pub fn nearest_common_ancestor(&self,
-                                   scope_a: CodeExtent,
-                                   scope_b: CodeExtent)
-                                   -> CodeExtent {
+                                   scope_a: Scope,
+                                   scope_b: Scope)
+                                   -> Scope {
         if scope_a == scope_b { return scope_a; }
 
         // [1] The initial values for `a_buf` and `b_buf` are not used.
         // The `ancestors_of` function will return some prefix that
         // is re-initialized with new values (or else fallback to a
         // heap-allocated vector).
-        let mut a_buf: [CodeExtent; 32] = [scope_a /* [1] */; 32];
-        let mut a_vec: Vec<CodeExtent> = vec![];
-        let mut b_buf: [CodeExtent; 32] = [scope_b /* [1] */; 32];
-        let mut b_vec: Vec<CodeExtent> = vec![];
-        let scope_map = &self.scope_map;
-        let a_ancestors = ancestors_of(scope_map, scope_a, &mut a_buf, &mut a_vec);
-        let b_ancestors = ancestors_of(scope_map, scope_b, &mut b_buf, &mut b_vec);
+        let mut a_buf: [Scope; 32] = [scope_a /* [1] */; 32];
+        let mut a_vec: Vec<Scope> = vec![];
+        let mut b_buf: [Scope; 32] = [scope_b /* [1] */; 32];
+        let mut b_vec: Vec<Scope> = vec![];
+        let parent_map = &self.parent_map;
+        let a_ancestors = ancestors_of(parent_map, scope_a, &mut a_buf, &mut a_vec);
+        let b_ancestors = ancestors_of(parent_map, scope_b, &mut b_buf, &mut b_vec);
         let mut a_index = a_ancestors.len() - 1;
         let mut b_index = b_ancestors.len() - 1;
 
@@ -489,12 +497,12 @@ impl<'tcx> RegionMaps {
             let a_root_scope = a_ancestors[a_index];
             let b_root_scope = a_ancestors[a_index];
             return match (a_root_scope, b_root_scope) {
-                (CodeExtent::DestructionScope(a_root_id),
-                 CodeExtent::DestructionScope(b_root_id)) => {
-                    if self.fn_is_enclosed_by(a_root_id, b_root_id) {
+                (Scope::Destruction(a_root_id),
+                 Scope::Destruction(b_root_id)) => {
+                    if self.closure_is_enclosed_by(a_root_id, b_root_id) {
                         // `a` is enclosed by `b`, hence `b` is the ancestor of everything in `a`
                         scope_b
-                    } else if self.fn_is_enclosed_by(b_root_id, a_root_id) {
+                    } else if self.closure_is_enclosed_by(b_root_id, a_root_id) {
                         // `b` is enclosed by `a`, hence `a` is the ancestor of everything in `b`
                         scope_a
                     } else {
@@ -503,7 +511,7 @@ impl<'tcx> RegionMaps {
                     }
                 }
                 _ => {
-                    // root ids are always Misc right now
+                    // root ids are always Node right now
                     bug!()
                 }
             };
@@ -521,18 +529,18 @@ impl<'tcx> RegionMaps {
             }
         }
 
-        fn ancestors_of<'a, 'tcx>(scope_map: &FxHashMap<CodeExtent, CodeExtent>,
-                                  scope: CodeExtent,
-                                  buf: &'a mut [CodeExtent; 32],
-                                  vec: &'a mut Vec<CodeExtent>)
-                                  -> &'a [CodeExtent] {
+        fn ancestors_of<'a, 'tcx>(parent_map: &FxHashMap<Scope, Scope>,
+                                  scope: Scope,
+                                  buf: &'a mut [Scope; 32],
+                                  vec: &'a mut Vec<Scope>)
+                                  -> &'a [Scope] {
             // debug!("ancestors_of(scope={:?})", scope);
             let mut scope = scope;
 
             let mut i = 0;
             while i < 32 {
                 buf[i] = scope;
-                match scope_map.get(&scope) {
+                match parent_map.get(&scope) {
                     Some(&superscope) => scope = superscope,
                     _ => return &buf[..i+1]
                 }
@@ -543,7 +551,7 @@ impl<'tcx> RegionMaps {
             vec.extend_from_slice(buf);
             loop {
                 vec.push(scope);
-                match scope_map.get(&scope) {
+                match parent_map.get(&scope) {
                     Some(&superscope) => scope = superscope,
                     _ => return &*vec
                 }
@@ -551,34 +559,38 @@ impl<'tcx> RegionMaps {
         }
     }
 
-    /// Assuming that the provided region was defined within this `RegionMaps`,
-    /// returns the outermost `CodeExtent` that the region outlives.
-    pub fn early_free_extent<'a, 'gcx>(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>,
+    /// Assuming that the provided region was defined within this `ScopeTree`,
+    /// returns the outermost `Scope` that the region outlives.
+    pub fn early_free_scope<'a, 'gcx>(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>,
                                        br: &ty::EarlyBoundRegion)
-                                       -> CodeExtent {
+                                       -> Scope {
         let param_owner = tcx.parent_def_id(br.def_id).unwrap();
 
         let param_owner_id = tcx.hir.as_local_node_id(param_owner).unwrap();
-        let body_id = tcx.hir.maybe_body_owned_by(param_owner_id).unwrap_or_else(|| {
+        let scope = tcx.hir.maybe_body_owned_by(param_owner_id).map(|body_id| {
+            tcx.hir.body(body_id).value.hir_id.local_id
+        }).unwrap_or_else(|| {
             // The lifetime was defined on node that doesn't own a body,
             // which in practice can only mean a trait or an impl, that
             // is the parent of a method, and that is enforced below.
             assert_eq!(Some(param_owner_id), self.root_parent,
-                       "free_extent: {:?} not recognized by the region maps for {:?}",
+                       "free_scope: {:?} not recognized by the \
+                        region scope tree for {:?} / {:?}",
                        param_owner,
-                       self.root_body.map(|body| tcx.hir.body_owner_def_id(body)));
+                       self.root_parent.map(|id| tcx.hir.local_def_id(id)),
+                       self.root_body.map(|hir_id| DefId::local(hir_id.owner)));
 
             // The trait/impl lifetime is in scope for the method's body.
-            self.root_body.unwrap()
+            self.root_body.unwrap().local_id
         });
 
-        CodeExtent::CallSiteScope(body_id)
+        Scope::CallSite(scope)
     }
 
-    /// Assuming that the provided region was defined within this `RegionMaps`,
-    /// returns the outermost `CodeExtent` that the region outlives.
-    pub fn free_extent<'a, 'gcx>(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>, fr: &ty::FreeRegion)
-                                 -> CodeExtent {
+    /// Assuming that the provided region was defined within this `ScopeTree`,
+    /// returns the outermost `Scope` that the region outlives.
+    pub fn free_scope<'a, 'gcx>(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>, fr: &ty::FreeRegion)
+                                 -> Scope {
         let param_owner = match fr.bound_region {
             ty::BoundRegion::BrNamed(def_id, _) => {
                 tcx.parent_def_id(def_id).unwrap()
@@ -591,13 +603,20 @@ impl<'tcx> RegionMaps {
         assert_eq!(param_owner, fr.scope);
 
         let param_owner_id = tcx.hir.as_local_node_id(param_owner).unwrap();
-        CodeExtent::CallSiteScope(tcx.hir.body_owned_by(param_owner_id))
+        let body_id = tcx.hir.body_owned_by(param_owner_id);
+        Scope::CallSite(tcx.hir.body(body_id).value.hir_id.local_id)
+    }
+
+    /// Checks whether the given scope contains a `yield`. If so,
+    /// returns `Some(span)` with the span of a yield we found.
+    pub fn yield_in_scope(&self, scope: Scope) -> Option<Span> {
+        self.yield_in_scope.get(&scope).cloned()
     }
 }
 
 /// Records the lifetime of a local variable as `cx.var_parent`
 fn record_var_lifetime(visitor: &mut RegionResolutionVisitor,
-                       var_id: ast::NodeId,
+                       var_id: hir::ItemLocalId,
                        _sp: Span) {
     match visitor.cx.var_parent {
         None => {
@@ -606,7 +625,7 @@ fn record_var_lifetime(visitor: &mut RegionResolutionVisitor,
             // extern fn isalnum(c: c_int) -> c_int
         }
         Some(parent_scope) =>
-            visitor.region_maps.record_var_scope(var_id, parent_scope),
+            visitor.scope_tree.record_var_scope(var_id, parent_scope),
     }
 }
 
@@ -640,7 +659,7 @@ fn resolve_block<'a, 'tcx>(visitor: &mut RegionResolutionVisitor<'a, 'tcx>, blk:
     // `other_argument()` has run and also the call to `quux(..)`
     // itself has returned.
 
-    visitor.enter_node_extent_with_dtor(blk.id);
+    visitor.enter_node_scope_with_dtor(blk.hir_id.local_id);
     visitor.cx.var_parent = visitor.cx.parent;
 
     {
@@ -657,9 +676,9 @@ fn resolve_block<'a, 'tcx>(visitor: &mut RegionResolutionVisitor<'a, 'tcx>, blk:
                 // has the previous subscope in the block as a parent,
                 // except for the first such subscope, which has the
                 // block itself as a parent.
-                visitor.enter_code_extent(
-                    CodeExtent::Remainder(BlockRemainder {
-                        block: blk.id,
+                visitor.enter_scope(
+                    Scope::Remainder(BlockRemainder {
+                        block: blk.hir_id.local_id,
                         first_statement_index: i as u32
                     })
                 );
@@ -674,39 +693,39 @@ fn resolve_block<'a, 'tcx>(visitor: &mut RegionResolutionVisitor<'a, 'tcx>, blk:
 }
 
 fn resolve_arm<'a, 'tcx>(visitor: &mut RegionResolutionVisitor<'a, 'tcx>, arm: &'tcx hir::Arm) {
-    visitor.terminating_scopes.insert(arm.body.id);
+    visitor.terminating_scopes.insert(arm.body.hir_id.local_id);
 
     if let Some(ref expr) = arm.guard {
-        visitor.terminating_scopes.insert(expr.id);
+        visitor.terminating_scopes.insert(expr.hir_id.local_id);
     }
 
     intravisit::walk_arm(visitor, arm);
 }
 
 fn resolve_pat<'a, 'tcx>(visitor: &mut RegionResolutionVisitor<'a, 'tcx>, pat: &'tcx hir::Pat) {
-    visitor.record_code_extent(CodeExtent::Misc(pat.id));
+    visitor.record_child_scope(Scope::Node(pat.hir_id.local_id));
 
     // If this is a binding then record the lifetime of that binding.
     if let PatKind::Binding(..) = pat.node {
-        record_var_lifetime(visitor, pat.id, pat.span);
+        record_var_lifetime(visitor, pat.hir_id.local_id, pat.span);
     }
 
     intravisit::walk_pat(visitor, pat);
 }
 
 fn resolve_stmt<'a, 'tcx>(visitor: &mut RegionResolutionVisitor<'a, 'tcx>, stmt: &'tcx hir::Stmt) {
-    let stmt_id = stmt.node.id();
+    let stmt_id = visitor.tcx.hir.node_to_hir_id(stmt.node.id()).local_id;
     debug!("resolve_stmt(stmt.id={:?})", stmt_id);
 
     // Every statement will clean up the temporaries created during
     // execution of that statement. Therefore each statement has an
-    // associated destruction scope that represents the extent of the
-    // statement plus its destructors, and thus the extent for which
+    // associated destruction scope that represents the scope of the
+    // statement plus its destructors, and thus the scope for which
     // regions referenced by the destructors need to survive.
     visitor.terminating_scopes.insert(stmt_id);
 
     let prev_parent = visitor.cx.parent;
-    visitor.enter_node_extent_with_dtor(stmt_id);
+    visitor.enter_node_scope_with_dtor(stmt_id);
 
     intravisit::walk_stmt(visitor, stmt);
 
@@ -717,11 +736,11 @@ fn resolve_expr<'a, 'tcx>(visitor: &mut RegionResolutionVisitor<'a, 'tcx>, expr:
     debug!("resolve_expr(expr.id={:?})", expr.id);
 
     let prev_cx = visitor.cx;
-    visitor.enter_node_extent_with_dtor(expr.id);
+    visitor.enter_node_scope_with_dtor(expr.hir_id.local_id);
 
     {
         let terminating_scopes = &mut visitor.terminating_scopes;
-        let mut terminating = |id: ast::NodeId| {
+        let mut terminating = |id: hir::ItemLocalId| {
             terminating_scopes.insert(id);
         };
         match expr.node {
@@ -733,27 +752,27 @@ fn resolve_expr<'a, 'tcx>(visitor: &mut RegionResolutionVisitor<'a, 'tcx>, expr:
             hir::ExprBinary(codemap::Spanned { node: hir::BiOr, .. }, _, ref r) => {
                 // For shortcircuiting operators, mark the RHS as a terminating
                 // scope since it only executes conditionally.
-                terminating(r.id);
+                terminating(r.hir_id.local_id);
             }
 
             hir::ExprIf(ref expr, ref then, Some(ref otherwise)) => {
-                terminating(expr.id);
-                terminating(then.id);
-                terminating(otherwise.id);
+                terminating(expr.hir_id.local_id);
+                terminating(then.hir_id.local_id);
+                terminating(otherwise.hir_id.local_id);
             }
 
             hir::ExprIf(ref expr, ref then, None) => {
-                terminating(expr.id);
-                terminating(then.id);
+                terminating(expr.hir_id.local_id);
+                terminating(then.hir_id.local_id);
             }
 
             hir::ExprLoop(ref body, _, _) => {
-                terminating(body.id);
+                terminating(body.hir_id.local_id);
             }
 
             hir::ExprWhile(ref expr, ref body, _) => {
-                terminating(expr.id);
-                terminating(body.id);
+                terminating(expr.hir_id.local_id);
+                terminating(body.hir_id.local_id);
             }
 
             hir::ExprMatch(..) => {
@@ -782,6 +801,29 @@ fn resolve_expr<'a, 'tcx>(visitor: &mut RegionResolutionVisitor<'a, 'tcx>, expr:
                 // record_superlifetime(new_cx, expr.callee_id);
             }
 
+            hir::ExprYield(..) => {
+                // Mark this expr's scope and all parent scopes as containing `yield`.
+                let mut scope = Scope::Node(expr.hir_id.local_id);
+                loop {
+                    match visitor.scope_tree.yield_in_scope.entry(scope) {
+                        // Another `yield` has already been found.
+                        Entry::Occupied(_) => break,
+
+                        Entry::Vacant(entry) => {
+                            entry.insert(expr.span);
+                        }
+                    }
+
+                    // Keep traversing up while we can.
+                    match visitor.scope_tree.parent_map.get(&scope) {
+                        // Don't cross from closure bodies to their parent.
+                        Some(&Scope::CallSite(_)) => break,
+                        Some(&superscope) => scope = superscope,
+                        None => break
+                    }
+                }
+            }
+
             _ => {}
         }
     }
@@ -789,7 +831,7 @@ fn resolve_expr<'a, 'tcx>(visitor: &mut RegionResolutionVisitor<'a, 'tcx>, expr:
     match expr.node {
         // Manually recurse over closures, because they are the only
         // case of nested bodies that share the parent environment.
-        hir::ExprClosure(.., body, _) => {
+        hir::ExprClosure(.., body, _, _) => {
             let body = visitor.tcx.hir.body(body);
             visitor.visit_body(body);
         }
@@ -801,16 +843,11 @@ fn resolve_expr<'a, 'tcx>(visitor: &mut RegionResolutionVisitor<'a, 'tcx>, expr:
 }
 
 fn resolve_local<'a, 'tcx>(visitor: &mut RegionResolutionVisitor<'a, 'tcx>,
-                           local: &'tcx hir::Local) {
-    debug!("resolve_local(local.id={:?},local.init={:?})",
-           local.id,local.init.is_some());
+                           pat: Option<&'tcx hir::Pat>,
+                           init: Option<&'tcx hir::Expr>) {
+    debug!("resolve_local(pat={:?}, init={:?})", pat, init);
 
-    // For convenience in trans, associate with the local-id the var
-    // scope that will be used for any bindings declared in this
-    // pattern.
     let blk_scope = visitor.cx.var_parent;
-    let blk_scope = blk_scope.expect("locals must be within a block");
-    visitor.region_maps.record_var_scope(local.id, blk_scope);
 
     // As an exception to the normal rules governing temporary
     // lifetimes, initializers in a let have a temporary lifetime
@@ -870,15 +907,22 @@ fn resolve_local<'a, 'tcx>(visitor: &mut RegionResolutionVisitor<'a, 'tcx>,
     //
     // FIXME(#6308) -- Note that `[]` patterns work more smoothly post-DST.
 
-    if let Some(ref expr) = local.init {
+    if let Some(expr) = init {
         record_rvalue_scope_if_borrow_expr(visitor, &expr, blk_scope);
 
-        if is_binding_pat(&local.pat) {
-            record_rvalue_scope(visitor, &expr, blk_scope);
+        if let Some(pat) = pat {
+            if is_binding_pat(pat) {
+                record_rvalue_scope(visitor, &expr, blk_scope);
+            }
         }
     }
 
-    intravisit::walk_local(visitor, local);
+    if let Some(pat) = pat {
+        visitor.visit_pat(pat);
+    }
+    if let Some(expr) = init {
+        visitor.visit_expr(expr);
+    }
 
     /// True if `pat` match the `P&` nonterminal:
     ///
@@ -952,7 +996,7 @@ fn resolve_local<'a, 'tcx>(visitor: &mut RegionResolutionVisitor<'a, 'tcx>,
     fn record_rvalue_scope_if_borrow_expr<'a, 'tcx>(
         visitor: &mut RegionResolutionVisitor<'a, 'tcx>,
         expr: &hir::Expr,
-        blk_id: CodeExtent)
+        blk_id: Option<Scope>)
     {
         match expr.node {
             hir::ExprAddrOf(_, ref subexpr) => {
@@ -1002,7 +1046,7 @@ fn resolve_local<'a, 'tcx>(visitor: &mut RegionResolutionVisitor<'a, 'tcx>,
     /// Note: ET is intended to match "rvalues or lvalues based on rvalues".
     fn record_rvalue_scope<'a, 'tcx>(visitor: &mut RegionResolutionVisitor<'a, 'tcx>,
                                      expr: &hir::Expr,
-                                     blk_scope: CodeExtent) {
+                                     blk_scope: Option<Scope>) {
         let mut expr = expr;
         loop {
             // Note: give all the expressions matching `ET` with the
@@ -1010,7 +1054,7 @@ fn resolve_local<'a, 'tcx>(visitor: &mut RegionResolutionVisitor<'a, 'tcx>,
             // because in trans if we must compile e.g. `*rvalue()`
             // into a temporary, we request the temporary scope of the
             // outer expression.
-            visitor.region_maps.record_rvalue_scope(expr.id, blk_scope);
+            visitor.scope_tree.record_rvalue_scope(expr.hir_id.local_id, blk_scope);
 
             match expr.node {
                 hir::ExprAddrOf(_, ref subexpr) |
@@ -1030,27 +1074,27 @@ fn resolve_local<'a, 'tcx>(visitor: &mut RegionResolutionVisitor<'a, 'tcx>,
 
 impl<'a, 'tcx> RegionResolutionVisitor<'a, 'tcx> {
     /// Records the current parent (if any) as the parent of `child_scope`.
-    fn record_code_extent(&mut self, child_scope: CodeExtent) {
+    fn record_child_scope(&mut self, child_scope: Scope) {
         let parent = self.cx.parent;
-        self.region_maps.record_code_extent(child_scope, parent);
+        self.scope_tree.record_scope_parent(child_scope, parent);
     }
 
     /// Records the current parent (if any) as the parent of `child_scope`,
     /// and sets `child_scope` as the new current parent.
-    fn enter_code_extent(&mut self, child_scope: CodeExtent) {
-        self.record_code_extent(child_scope);
+    fn enter_scope(&mut self, child_scope: Scope) {
+        self.record_child_scope(child_scope);
         self.cx.parent = Some(child_scope);
     }
 
-    fn enter_node_extent_with_dtor(&mut self, id: ast::NodeId) {
+    fn enter_node_scope_with_dtor(&mut self, id: hir::ItemLocalId) {
         // If node was previously marked as a terminating scope during the
         // recursive visit of its parent node in the AST, then we need to
-        // account for the destruction scope representing the extent of
+        // account for the destruction scope representing the scope of
         // the destructors that run immediately after it completes.
         if self.terminating_scopes.contains(&id) {
-            self.enter_code_extent(CodeExtent::DestructionScope(id));
+            self.enter_scope(Scope::Destruction(id));
         }
-        self.enter_code_extent(CodeExtent::Misc(id));
+        self.enter_scope(Scope::Node(id));
     }
 }
 
@@ -1074,21 +1118,16 @@ impl<'a, 'tcx> Visitor<'tcx> for RegionResolutionVisitor<'a, 'tcx> {
                self.cx.parent);
 
         let outer_cx = self.cx;
-        let outer_ts = mem::replace(&mut self.terminating_scopes, NodeSet());
-
-        // Only functions have an outer terminating (drop) scope,
-        // while temporaries in constant initializers are 'static.
-        if let MirSource::Fn(_) = MirSource::from_node(self.tcx, owner_id) {
-            self.terminating_scopes.insert(body_id.node_id);
-        }
+        let outer_ts = mem::replace(&mut self.terminating_scopes, FxHashSet());
+        self.terminating_scopes.insert(body.value.hir_id.local_id);
 
         if let Some(root_id) = self.cx.root_id {
-            self.region_maps.record_fn_parent(body_id.node_id, root_id);
+            self.scope_tree.record_closure_parent(body.value.hir_id.local_id, root_id);
         }
-        self.cx.root_id = Some(body_id.node_id);
+        self.cx.root_id = Some(body.value.hir_id.local_id);
 
-        self.enter_code_extent(CodeExtent::CallSiteScope(body_id));
-        self.enter_code_extent(CodeExtent::ParameterScope(body_id));
+        self.enter_scope(Scope::CallSite(body.value.hir_id.local_id));
+        self.enter_scope(Scope::Arguments(body.value.hir_id.local_id));
 
         // The arguments and `self` are parented to the fn.
         self.cx.var_parent = self.cx.parent.take();
@@ -1098,7 +1137,30 @@ impl<'a, 'tcx> Visitor<'tcx> for RegionResolutionVisitor<'a, 'tcx> {
 
         // The body of the every fn is a root scope.
         self.cx.parent = self.cx.var_parent;
-        self.visit_expr(&body.value);
+        if let MirSource::Fn(_) = MirSource::from_node(self.tcx, owner_id) {
+            self.visit_expr(&body.value);
+        } else {
+            // Only functions have an outer terminating (drop) scope, while
+            // temporaries in constant initializers may be 'static, but only
+            // according to rvalue lifetime semantics, using the same
+            // syntactical rules used for let initializers.
+            //
+            // E.g. in `let x = &f();`, the temporary holding the result from
+            // the `f()` call lives for the entirety of the surrounding block.
+            //
+            // Similarly, `const X: ... = &f();` would have the result of `f()`
+            // live for `'static`, implying (if Drop restrictions on constants
+            // ever get lifted) that the value *could* have a destructor, but
+            // it'd get leaked instead of the destructor running during the
+            // evaluation of `X` (if at all allowed by CTFE).
+            //
+            // However, `const Y: ... = g(&f());`, like `let y = g(&f());`,
+            // would *not* let the `f()` temporary escape into an outer scope
+            // (i.e. `'static`), which means that after `g` returns, it drops,
+            // and all the associated destruction scope rules apply.
+            self.cx.var_parent = None;
+            resolve_local(self, None, Some(&body.value));
+        }
 
         // Restore context we had at the start.
         self.cx = outer_cx;
@@ -1118,32 +1180,33 @@ impl<'a, 'tcx> Visitor<'tcx> for RegionResolutionVisitor<'a, 'tcx> {
         resolve_expr(self, ex);
     }
     fn visit_local(&mut self, l: &'tcx Local) {
-        resolve_local(self, l);
+        resolve_local(self, Some(&l.pat), l.init.as_ref().map(|e| &**e));
     }
 }
 
-fn region_maps<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId)
-    -> Rc<RegionMaps>
+fn region_scope_tree<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId)
+    -> Rc<ScopeTree>
 {
     let closure_base_def_id = tcx.closure_base_def_id(def_id);
     if closure_base_def_id != def_id {
-        return tcx.region_maps(closure_base_def_id);
+        return tcx.region_scope_tree(closure_base_def_id);
     }
 
     let id = tcx.hir.as_local_node_id(def_id).unwrap();
-    let maps = if let Some(body) = tcx.hir.maybe_body_owned_by(id) {
+    let scope_tree = if let Some(body_id) = tcx.hir.maybe_body_owned_by(id) {
         let mut visitor = RegionResolutionVisitor {
             tcx,
-            region_maps: RegionMaps::new(),
+            scope_tree: ScopeTree::default(),
             cx: Context {
                 root_id: None,
                 parent: None,
                 var_parent: None,
             },
-            terminating_scopes: NodeSet(),
+            terminating_scopes: FxHashSet(),
         };
 
-        visitor.region_maps.root_body = Some(body);
+        let body = tcx.hir.body(body_id);
+        visitor.scope_tree.root_body = Some(body.value.hir_id);
 
         // If the item is an associated const or a method,
         // record its impl/trait parent, as it can also have
@@ -1151,24 +1214,24 @@ fn region_maps<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId)
         match tcx.hir.get(id) {
             hir::map::NodeImplItem(_) |
             hir::map::NodeTraitItem(_) => {
-                visitor.region_maps.root_parent = Some(tcx.hir.get_parent(id));
+                visitor.scope_tree.root_parent = Some(tcx.hir.get_parent(id));
             }
             _ => {}
         }
 
-        visitor.visit_body(tcx.hir.body(body));
+        visitor.visit_body(body);
 
-        visitor.region_maps
+        visitor.scope_tree
     } else {
-        RegionMaps::new()
+        ScopeTree::default()
     };
 
-    Rc::new(maps)
+    Rc::new(scope_tree)
 }
 
 pub fn provide(providers: &mut Providers) {
     *providers = Providers {
-        region_maps,
+        region_scope_tree,
         ..*providers
     };
 }
diff --git a/src/librustc/mir/mod.rs b/src/librustc/mir/mod.rs
index 74ce68b351df9..cf3d7c3642a5f 100644
--- a/src/librustc/mir/mod.rs
+++ b/src/librustc/mir/mod.rs
@@ -12,7 +12,7 @@
 
 use graphviz::IntoCow;
 use middle::const_val::ConstVal;
-use middle::region::CodeExtent;
+use middle::region;
 use rustc_const_math::{ConstUsize, ConstInt, ConstMathErr};
 use rustc_data_structures::indexed_vec::{IndexVec, Idx};
 use rustc_data_structures::control_flow_graph::dominators::{Dominators, dominators};
@@ -21,7 +21,7 @@ use rustc_data_structures::control_flow_graph::ControlFlowGraph;
 use hir::def::CtorKind;
 use hir::def_id::DefId;
 use ty::subst::{Subst, Substs};
-use ty::{self, AdtDef, ClosureSubsts, Region, Ty};
+use ty::{self, AdtDef, ClosureSubsts, Region, Ty, GeneratorInterior};
 use ty::fold::{TypeFoldable, TypeFolder, TypeVisitor};
 use util::ppaux;
 use rustc_back::slice;
@@ -104,6 +104,15 @@ pub struct Mir<'tcx> {
     /// Return type of the function.
     pub return_ty: Ty<'tcx>,
 
+    /// Yield type of the function, if it is a generator.
+    pub yield_ty: Option<Ty<'tcx>>,
+
+    /// Generator drop glue
+    pub generator_drop: Option<Box<Mir<'tcx>>>,
+
+    /// The layout of a generator. Produced by the state transformation.
+    pub generator_layout: Option<GeneratorLayout<'tcx>>,
+
     /// Declarations of locals.
     ///
     /// The first local is the return value pointer, followed by `arg_count`
@@ -144,6 +153,7 @@ impl<'tcx> Mir<'tcx> {
                visibility_scopes: IndexVec<VisibilityScope, VisibilityScopeData>,
                promoted: IndexVec<Promoted, Mir<'tcx>>,
                return_ty: Ty<'tcx>,
+               yield_ty: Option<Ty<'tcx>>,
                local_decls: IndexVec<Local, LocalDecl<'tcx>>,
                arg_count: usize,
                upvar_decls: Vec<UpvarDecl>,
@@ -159,6 +169,9 @@ impl<'tcx> Mir<'tcx> {
             visibility_scopes,
             promoted,
             return_ty,
+            yield_ty,
+            generator_drop: None,
+            generator_layout: None,
             local_decls,
             arg_count,
             upvar_decls,
@@ -270,6 +283,9 @@ impl_stable_hash_for!(struct Mir<'tcx> {
     visibility_scopes,
     promoted,
     return_ty,
+    yield_ty,
+    generator_drop,
+    generator_layout,
     local_decls,
     arg_count,
     upvar_decls,
@@ -395,6 +411,22 @@ pub struct LocalDecl<'tcx> {
     /// True if this corresponds to a user-declared local variable.
     pub is_user_variable: bool,
 
+    /// True if this is an internal local
+    ///
+    /// These locals are not based on types in the source code and are only used
+    /// for drop flags at the moment.
+    ///
+    /// The generator transformation will sanity check the locals which are live
+    /// across a suspension point against the type components of the generator
+    /// which type checking knows are live across a suspension point. We need to
+    /// flag drop flags to avoid triggering this check as they are introduced
+    /// after typeck.
+    ///
+    /// This should be sound because the drop flags are fully algebraic, and
+    /// therefore don't affect the OIBIT or outlives properties of the
+    /// generator.
+    pub internal: bool,
+
     /// Type of this local.
     pub ty: Ty<'tcx>,
 
@@ -420,6 +452,23 @@ impl<'tcx> LocalDecl<'tcx> {
                 span,
                 scope: ARGUMENT_VISIBILITY_SCOPE
             },
+            internal: false,
+            is_user_variable: false
+        }
+    }
+
+    /// Create a new `LocalDecl` for a internal temporary.
+    #[inline]
+    pub fn new_internal(ty: Ty<'tcx>, span: Span) -> Self {
+        LocalDecl {
+            mutability: Mutability::Mut,
+            ty,
+            name: None,
+            source_info: SourceInfo {
+                span,
+                scope: ARGUMENT_VISIBILITY_SCOPE
+            },
+            internal: true,
             is_user_variable: false
         }
     }
@@ -436,6 +485,7 @@ impl<'tcx> LocalDecl<'tcx> {
                 span,
                 scope: ARGUMENT_VISIBILITY_SCOPE
             },
+            internal: false,
             name: None,     // FIXME maybe we do want some name here?
             is_user_variable: false
         }
@@ -567,7 +617,20 @@ pub enum TerminatorKind<'tcx> {
         msg: AssertMessage<'tcx>,
         target: BasicBlock,
         cleanup: Option<BasicBlock>
-    }
+    },
+
+    /// A suspend point
+    Yield {
+        /// The value to return
+        value: Operand<'tcx>,
+        /// Where to resume to
+        resume: BasicBlock,
+        /// Cleanup to be done if the generator is dropped at this suspend point
+        drop: Option<BasicBlock>,
+    },
+
+    /// Indicates the end of the dropping of a generator
+    GeneratorDrop,
 }
 
 impl<'tcx> Terminator<'tcx> {
@@ -597,7 +660,7 @@ impl<'tcx> TerminatorKind<'tcx> {
         match *self {
             Goto { target: ref b } => slice::ref_slice(b).into_cow(),
             SwitchInt { targets: ref b, .. } => b[..].into_cow(),
-            Resume => (&[]).into_cow(),
+            Resume | GeneratorDrop => (&[]).into_cow(),
             Return => (&[]).into_cow(),
             Unreachable => (&[]).into_cow(),
             Call { destination: Some((_, t)), cleanup: Some(c), .. } => vec![t, c].into_cow(),
@@ -605,6 +668,8 @@ impl<'tcx> TerminatorKind<'tcx> {
                 slice::ref_slice(t).into_cow(),
             Call { destination: None, cleanup: Some(ref c), .. } => slice::ref_slice(c).into_cow(),
             Call { destination: None, cleanup: None, .. } => (&[]).into_cow(),
+            Yield { resume: t, drop: Some(c), .. } => vec![t, c].into_cow(),
+            Yield { resume: ref t, drop: None, .. } => slice::ref_slice(t).into_cow(),
             DropAndReplace { target, unwind: Some(unwind), .. } |
             Drop { target, unwind: Some(unwind), .. } => {
                 vec![target, unwind].into_cow()
@@ -625,13 +690,15 @@ impl<'tcx> TerminatorKind<'tcx> {
         match *self {
             Goto { target: ref mut b } => vec![b],
             SwitchInt { targets: ref mut b, .. } => b.iter_mut().collect(),
-            Resume => Vec::new(),
+            Resume | GeneratorDrop => Vec::new(),
             Return => Vec::new(),
             Unreachable => Vec::new(),
             Call { destination: Some((_, ref mut t)), cleanup: Some(ref mut c), .. } => vec![t, c],
             Call { destination: Some((_, ref mut t)), cleanup: None, .. } => vec![t],
             Call { destination: None, cleanup: Some(ref mut c), .. } => vec![c],
             Call { destination: None, cleanup: None, .. } => vec![],
+            Yield { resume: ref mut t, drop: Some(ref mut c), .. } => vec![t, c],
+            Yield { resume: ref mut t, drop: None, .. } => vec![t],
             DropAndReplace { ref mut target, unwind: Some(ref mut unwind), .. } |
             Drop { ref mut target, unwind: Some(ref mut unwind), .. } => vec![target, unwind],
             DropAndReplace { ref mut target, unwind: None, .. } |
@@ -664,6 +731,14 @@ impl<'tcx> BasicBlockData<'tcx> {
     pub fn terminator_mut(&mut self) -> &mut Terminator<'tcx> {
         self.terminator.as_mut().expect("invalid terminator state")
     }
+
+    pub fn retain_statements<F>(&mut self, mut f: F) where F: FnMut(&mut Statement) -> bool {
+        for s in &mut self.statements {
+            if !f(s) {
+                s.kind = StatementKind::Nop;
+            }
+        }
+    }
 }
 
 impl<'tcx> Debug for TerminatorKind<'tcx> {
@@ -703,7 +778,9 @@ impl<'tcx> TerminatorKind<'tcx> {
             Goto { .. } => write!(fmt, "goto"),
             SwitchInt { discr: ref lv, .. } => write!(fmt, "switchInt({:?})", lv),
             Return => write!(fmt, "return"),
+            GeneratorDrop => write!(fmt, "generator_drop"),
             Resume => write!(fmt, "resume"),
+            Yield { ref value, .. } => write!(fmt, "_1 = suspend({:?})", value),
             Unreachable => write!(fmt, "unreachable"),
             Drop { ref location, .. } => write!(fmt, "drop({:?})", location),
             DropAndReplace { ref location, ref value, .. } =>
@@ -737,6 +814,12 @@ impl<'tcx> TerminatorKind<'tcx> {
                     AssertMessage::Math(ref err) => {
                         write!(fmt, "{:?}", err.description())?;
                     }
+                    AssertMessage::GeneratorResumedAfterReturn => {
+                        write!(fmt, "{:?}", "generator resumed after completion")?;
+                    }
+                    AssertMessage::GeneratorResumedAfterPanic => {
+                        write!(fmt, "{:?}", "generator resumed after panicking")?;
+                    }
                 }
 
                 write!(fmt, ")")
@@ -748,7 +831,7 @@ impl<'tcx> TerminatorKind<'tcx> {
     pub fn fmt_successor_labels(&self) -> Vec<Cow<'static, str>> {
         use self::TerminatorKind::*;
         match *self {
-            Return | Resume | Unreachable => vec![],
+            Return | Resume | Unreachable | GeneratorDrop => vec![],
             Goto { .. } => vec!["".into()],
             SwitchInt { ref values, .. } => {
                 values.iter()
@@ -765,6 +848,9 @@ impl<'tcx> TerminatorKind<'tcx> {
             Call { destination: Some(_), cleanup: None, .. } => vec!["return".into_cow()],
             Call { destination: None, cleanup: Some(_), .. } => vec!["unwind".into_cow()],
             Call { destination: None, cleanup: None, .. } => vec![],
+            Yield { drop: Some(_), .. } =>
+                vec!["resume".into_cow(), "drop".into_cow()],
+            Yield { drop: None, .. } => vec!["resume".into_cow()],
             DropAndReplace { unwind: None, .. } |
             Drop { unwind: None, .. } => vec!["return".into_cow()],
             DropAndReplace { unwind: Some(_), .. } |
@@ -784,7 +870,9 @@ pub enum AssertMessage<'tcx> {
         len: Operand<'tcx>,
         index: Operand<'tcx>
     },
-    Math(ConstMathErr)
+    Math(ConstMathErr),
+    GeneratorResumedAfterReturn,
+    GeneratorResumedAfterPanic,
 }
 
 ///////////////////////////////////////////////////////////////////////////
@@ -813,10 +901,10 @@ pub enum StatementKind<'tcx> {
     SetDiscriminant { lvalue: Lvalue<'tcx>, variant_index: usize },
 
     /// Start a live range for the storage of the local.
-    StorageLive(Lvalue<'tcx>),
+    StorageLive(Local),
 
     /// End the current live range for the storage of the local.
-    StorageDead(Lvalue<'tcx>),
+    StorageDead(Local),
 
     /// Execute a piece of inline Assembly.
     InlineAsm {
@@ -830,9 +918,9 @@ pub enum StatementKind<'tcx> {
     /// See <https://internals.rust-lang.org/t/types-as-contracts/5562/73> for more details.
     Validate(ValidationOp, Vec<ValidationOperand<'tcx, Lvalue<'tcx>>>),
 
-    /// Mark one terminating point of an extent (i.e. static region).
+    /// Mark one terminating point of a region scope (i.e. static region).
     /// (The starting point(s) arise implicitly from borrows.)
-    EndRegion(CodeExtent),
+    EndRegion(region::Scope),
 
     /// No-op. Useful for deleting instructions without affecting statement indices.
     Nop,
@@ -851,7 +939,7 @@ pub enum ValidationOp {
     Release,
     /// Recursive traverse the *mutable* part of the type and relinquish all exclusive
     /// access *until* the given region ends.  Then, access will be recovered.
-    Suspend(CodeExtent),
+    Suspend(region::Scope),
 }
 
 impl Debug for ValidationOp {
@@ -871,7 +959,7 @@ impl Debug for ValidationOp {
 pub struct ValidationOperand<'tcx, T> {
     pub lval: T,
     pub ty: Ty<'tcx>,
-    pub re: Option<CodeExtent>,
+    pub re: Option<region::Scope>,
     pub mutbl: hir::Mutability,
 }
 
@@ -989,12 +1077,12 @@ pub enum ProjectionElem<'tcx, V, T> {
 }
 
 /// Alias for projections as they appear in lvalues, where the base is an lvalue
-/// and the index is an operand.
-pub type LvalueProjection<'tcx> = Projection<'tcx, Lvalue<'tcx>, Operand<'tcx>, Ty<'tcx>>;
+/// and the index is a local.
+pub type LvalueProjection<'tcx> = Projection<'tcx, Lvalue<'tcx>, Local, Ty<'tcx>>;
 
 /// Alias for projections as they appear in lvalues, where the base is an lvalue
-/// and the index is an operand.
-pub type LvalueElem<'tcx> = ProjectionElem<'tcx, Operand<'tcx>, Ty<'tcx>>;
+/// and the index is a local.
+pub type LvalueElem<'tcx> = ProjectionElem<'tcx, Local, Ty<'tcx>>;
 
 newtype_index!(Field, "field");
 
@@ -1011,7 +1099,7 @@ impl<'tcx> Lvalue<'tcx> {
         self.elem(ProjectionElem::Downcast(adt_def, variant_index))
     }
 
-    pub fn index(self, index: Operand<'tcx>) -> Lvalue<'tcx> {
+    pub fn index(self, index: Local) -> Lvalue<'tcx> {
         self.elem(ProjectionElem::Index(index))
     }
 
@@ -1178,6 +1266,7 @@ pub enum AggregateKind<'tcx> {
     /// number and is present only for union expressions.
     Adt(&'tcx AdtDef, usize, &'tcx Substs<'tcx>, Option<usize>),
     Closure(DefId, ClosureSubsts<'tcx>),
+    Generator(DefId, ClosureSubsts<'tcx>, GeneratorInterior<'tcx>),
 }
 
 #[derive(Copy, Clone, Debug, PartialEq, Eq, RustcEncodable, RustcDecodable)]
@@ -1339,6 +1428,31 @@ impl<'tcx> Debug for Rvalue<'tcx> {
                             write!(fmt, "[closure]")
                         }
                     }),
+
+                    AggregateKind::Generator(def_id, _, _) => ty::tls::with(|tcx| {
+                        if let Some(node_id) = tcx.hir.as_local_node_id(def_id) {
+                            let name = format!("[generator@{:?}]", tcx.hir.span(node_id));
+                            let mut struct_fmt = fmt.debug_struct(&name);
+
+                            tcx.with_freevars(node_id, |freevars| {
+                                for (freevar, lv) in freevars.iter().zip(lvs) {
+                                    let def_id = freevar.def.def_id();
+                                    let var_id = tcx.hir.as_local_node_id(def_id).unwrap();
+                                    let var_name = tcx.local_var_name_str(var_id);
+                                    struct_fmt.field(&var_name, lv);
+                                }
+                                struct_fmt.field("$state", &lvs[freevars.len()]);
+                                for i in (freevars.len() + 1)..lvs.len() {
+                                    struct_fmt.field(&format!("${}", i - freevars.len() - 1),
+                                                     &lvs[i]);
+                                }
+                            });
+
+                            struct_fmt.finish()
+                        } else {
+                            write!(fmt, "[generator]")
+                        }
+                    }),
                 }
             }
         }
@@ -1483,6 +1597,11 @@ impl Location {
     }
 }
 
+/// The layout of generator state
+#[derive(Clone, Debug, RustcEncodable, RustcDecodable)]
+pub struct GeneratorLayout<'tcx> {
+    pub fields: Vec<LocalDecl<'tcx>>,
+}
 
 /*
  * TypeFoldable implementations for MIR types
@@ -1495,6 +1614,9 @@ impl<'tcx> TypeFoldable<'tcx> for Mir<'tcx> {
             visibility_scopes: self.visibility_scopes.clone(),
             promoted: self.promoted.fold_with(folder),
             return_ty: self.return_ty.fold_with(folder),
+            yield_ty: self.yield_ty.fold_with(folder),
+            generator_drop: self.generator_drop.fold_with(folder),
+            generator_layout: self.generator_layout.fold_with(folder),
             local_decls: self.local_decls.fold_with(folder),
             arg_count: self.arg_count,
             upvar_decls: self.upvar_decls.clone(),
@@ -1506,12 +1628,27 @@ impl<'tcx> TypeFoldable<'tcx> for Mir<'tcx> {
 
     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
         self.basic_blocks.visit_with(visitor) ||
+        self.generator_drop.visit_with(visitor) ||
+        self.generator_layout.visit_with(visitor) ||
+        self.yield_ty.visit_with(visitor) ||
         self.promoted.visit_with(visitor)     ||
         self.return_ty.visit_with(visitor)    ||
         self.local_decls.visit_with(visitor)
     }
 }
 
+impl<'tcx> TypeFoldable<'tcx> for GeneratorLayout<'tcx> {
+    fn super_fold_with<'gcx: 'tcx, F: TypeFolder<'gcx, 'tcx>>(&self, folder: &mut F) -> Self {
+        GeneratorLayout {
+            fields: self.fields.fold_with(folder),
+        }
+    }
+
+    fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        self.fields.visit_with(visitor)
+    }
+}
+
 impl<'tcx> TypeFoldable<'tcx> for LocalDecl<'tcx> {
     fn super_fold_with<'gcx: 'tcx, F: TypeFolder<'gcx, 'tcx>>(&self, folder: &mut F) -> Self {
         LocalDecl {
@@ -1564,19 +1701,19 @@ impl<'tcx> TypeFoldable<'tcx> for Statement<'tcx> {
                 lvalue: lvalue.fold_with(folder),
                 variant_index,
             },
-            StorageLive(ref lval) => StorageLive(lval.fold_with(folder)),
-            StorageDead(ref lval) => StorageDead(lval.fold_with(folder)),
+            StorageLive(ref local) => StorageLive(local.fold_with(folder)),
+            StorageDead(ref local) => StorageDead(local.fold_with(folder)),
             InlineAsm { ref asm, ref outputs, ref inputs } => InlineAsm {
                 asm: asm.clone(),
                 outputs: outputs.fold_with(folder),
                 inputs: inputs.fold_with(folder)
             },
 
-            // Note for future: If we want to expose the extents
+            // Note for future: If we want to expose the region scopes
             // during the fold, we need to either generalize EndRegion
             // to carry `[ty::Region]`, or extend the `TypeFolder`
-            // trait with a `fn fold_extent`.
-            EndRegion(ref extent) => EndRegion(extent.clone()),
+            // trait with a `fn fold_scope`.
+            EndRegion(ref region_scope) => EndRegion(region_scope.clone()),
 
             Validate(ref op, ref lvals) =>
                 Validate(op.clone(),
@@ -1595,17 +1732,17 @@ impl<'tcx> TypeFoldable<'tcx> for Statement<'tcx> {
 
         match self.kind {
             Assign(ref lval, ref rval) => { lval.visit_with(visitor) || rval.visit_with(visitor) }
-            SetDiscriminant { ref lvalue, .. } |
-            StorageLive(ref lvalue) |
-            StorageDead(ref lvalue) => lvalue.visit_with(visitor),
+            SetDiscriminant { ref lvalue, .. } => lvalue.visit_with(visitor),
+            StorageLive(ref local) |
+            StorageDead(ref local) => local.visit_with(visitor),
             InlineAsm { ref outputs, ref inputs, .. } =>
                 outputs.visit_with(visitor) || inputs.visit_with(visitor),
 
-            // Note for future: If we want to expose the extents
+            // Note for future: If we want to expose the region scopes
             // during the visit, we need to either generalize EndRegion
             // to carry `[ty::Region]`, or extend the `TypeVisitor`
-            // trait with a `fn visit_extent`.
-            EndRegion(ref _extent) => false,
+            // trait with a `fn visit_scope`.
+            EndRegion(ref _scope) => false,
 
             Validate(ref _op, ref lvalues) =>
                 lvalues.iter().any(|ty_and_lvalue| ty_and_lvalue.visit_with(visitor)),
@@ -1638,6 +1775,11 @@ impl<'tcx> TypeFoldable<'tcx> for Terminator<'tcx> {
                 target,
                 unwind,
             },
+            Yield { ref value, resume, drop } => Yield {
+                value: value.fold_with(folder),
+                resume: resume,
+                drop: drop,
+            },
             Call { ref func, ref args, ref destination, cleanup } => {
                 let dest = destination.as_ref().map(|&(ref loc, dest)| {
                     (loc.fold_with(folder), dest)
@@ -1667,6 +1809,7 @@ impl<'tcx> TypeFoldable<'tcx> for Terminator<'tcx> {
                     cleanup,
                 }
             },
+            GeneratorDrop => GeneratorDrop,
             Resume => Resume,
             Return => Return,
             Unreachable => Unreachable,
@@ -1686,6 +1829,8 @@ impl<'tcx> TypeFoldable<'tcx> for Terminator<'tcx> {
             Drop { ref location, ..} => location.visit_with(visitor),
             DropAndReplace { ref location, ref value, ..} =>
                 location.visit_with(visitor) || value.visit_with(visitor),
+            Yield { ref value, ..} =>
+                value.visit_with(visitor),
             Call { ref func, ref args, ref destination, .. } => {
                 let dest = if let Some((ref loc, _)) = *destination {
                     loc.visit_with(visitor)
@@ -1706,6 +1851,7 @@ impl<'tcx> TypeFoldable<'tcx> for Terminator<'tcx> {
             Goto { .. } |
             Resume |
             Return |
+            GeneratorDrop |
             Unreachable => false
         }
     }
@@ -1751,7 +1897,11 @@ impl<'tcx> TypeFoldable<'tcx> for Rvalue<'tcx> {
                     AggregateKind::Adt(def, v, substs, n) =>
                         AggregateKind::Adt(def, v, substs.fold_with(folder), n),
                     AggregateKind::Closure(id, substs) =>
-                        AggregateKind::Closure(id, substs.fold_with(folder))
+                        AggregateKind::Closure(id, substs.fold_with(folder)),
+                    AggregateKind::Generator(id, substs, interior) =>
+                        AggregateKind::Generator(id,
+                                                 substs.fold_with(folder),
+                                                 interior.fold_with(folder)),
                 };
                 Aggregate(kind, fields.fold_with(folder))
             }
@@ -1777,7 +1927,9 @@ impl<'tcx> TypeFoldable<'tcx> for Rvalue<'tcx> {
                     AggregateKind::Array(ty) => ty.visit_with(visitor),
                     AggregateKind::Tuple => false,
                     AggregateKind::Adt(_, _, substs, _) => substs.visit_with(visitor),
-                    AggregateKind::Closure(_, substs) => substs.visit_with(visitor)
+                    AggregateKind::Closure(_, substs) => substs.visit_with(visitor),
+                    AggregateKind::Generator(_, substs, interior) => substs.visit_with(visitor) ||
+                        interior.visit_with(visitor),
                 }) || fields.visit_with(visitor)
             }
         }
diff --git a/src/librustc/mir/tcx.rs b/src/librustc/mir/tcx.rs
index a801804d502a1..eb403442f4639 100644
--- a/src/librustc/mir/tcx.rs
+++ b/src/librustc/mir/tcx.rs
@@ -207,6 +207,9 @@ impl<'tcx> Rvalue<'tcx> {
                     AggregateKind::Closure(did, substs) => {
                         tcx.mk_closure_from_closure_substs(did, substs)
                     }
+                    AggregateKind::Generator(did, substs, interior) => {
+                        tcx.mk_generator(did, substs, interior)
+                    }
                 }
             }
         }
diff --git a/src/librustc/mir/transform.rs b/src/librustc/mir/transform.rs
index aa91123ef6952..f29405e665051 100644
--- a/src/librustc/mir/transform.rs
+++ b/src/librustc/mir/transform.rs
@@ -33,7 +33,10 @@ pub enum MirSource {
     Static(NodeId, hir::Mutability),
 
     /// Promoted rvalues within a function.
-    Promoted(NodeId, Promoted)
+    Promoted(NodeId, Promoted),
+
+    /// Drop glue for a generator.
+    GeneratorDrop(NodeId),
 }
 
 impl<'a, 'tcx> MirSource {
@@ -70,6 +73,7 @@ impl<'a, 'tcx> MirSource {
         match *self {
             MirSource::Fn(id) |
             MirSource::Const(id) |
+            MirSource::GeneratorDrop(id) |
             MirSource::Static(id, _) |
             MirSource::Promoted(id, _) => id
         }
diff --git a/src/librustc/mir/visit.rs b/src/librustc/mir/visit.rs
index a6d115bf03912..f26505c6d0237 100644
--- a/src/librustc/mir/visit.rs
+++ b/src/librustc/mir/visit.rs
@@ -11,7 +11,7 @@
 use middle::const_val::ConstVal;
 use hir::def_id::DefId;
 use ty::subst::Substs;
-use ty::{ClosureSubsts, Region, Ty};
+use ty::{ClosureSubsts, Region, Ty, GeneratorInterior};
 use mir::*;
 use rustc_const_math::ConstUsize;
 use syntax_pos::Span;
@@ -226,6 +226,12 @@ macro_rules! make_mir_visitor {
                 self.super_closure_substs(substs);
             }
 
+            fn visit_generator_interior(&mut self,
+                                    interior: & $($mutability)* GeneratorInterior<'tcx>,
+                                    _: Location) {
+                self.super_generator_interior(interior);
+            }
+
             fn visit_const_val(&mut self,
                                const_val: & $($mutability)* ConstVal,
                                _: Location) {
@@ -249,6 +255,12 @@ macro_rules! make_mir_visitor {
                 self.super_local_decl(local_decl);
             }
 
+            fn visit_local(&mut self,
+                            _local: & $($mutability)* Local,
+                            _context: LvalueContext<'tcx>,
+                            _location: Location) {
+            }
+
             fn visit_visibility_scope(&mut self,
                                       scope: & $($mutability)* VisibilityScope) {
                 self.super_visibility_scope(scope);
@@ -348,11 +360,11 @@ macro_rules! make_mir_visitor {
                     StatementKind::SetDiscriminant{ ref $($mutability)* lvalue, .. } => {
                         self.visit_lvalue(lvalue, LvalueContext::Store, location);
                     }
-                    StatementKind::StorageLive(ref $($mutability)* lvalue) => {
-                        self.visit_lvalue(lvalue, LvalueContext::StorageLive, location);
+                    StatementKind::StorageLive(ref $($mutability)* local) => {
+                        self.visit_local(local, LvalueContext::StorageLive, location);
                     }
-                    StatementKind::StorageDead(ref $($mutability)* lvalue) => {
-                        self.visit_lvalue(lvalue, LvalueContext::StorageDead, location);
+                    StatementKind::StorageDead(ref $($mutability)* local) => {
+                        self.visit_local(local, LvalueContext::StorageDead, location);
                     }
                     StatementKind::InlineAsm { ref $($mutability)* outputs,
                                                ref $($mutability)* inputs,
@@ -415,6 +427,7 @@ macro_rules! make_mir_visitor {
 
                     TerminatorKind::Resume |
                     TerminatorKind::Return |
+                    TerminatorKind::GeneratorDrop |
                     TerminatorKind::Unreachable => {
                     }
 
@@ -461,6 +474,15 @@ macro_rules! make_mir_visitor {
                         self.visit_branch(block, target);
                         cleanup.map(|t| self.visit_branch(block, t));
                     }
+
+                    TerminatorKind::Yield { ref $($mutability)* value,
+                                              resume,
+                                              drop } => {
+                        self.visit_operand(value, source_location);
+                        self.visit_branch(block, resume);
+                        drop.map(|t| self.visit_branch(block, t));
+                    }
+
                 }
             }
 
@@ -475,7 +497,9 @@ macro_rules! make_mir_visitor {
                         self.visit_operand(len, location);
                         self.visit_operand(index, location);
                     }
-                    AssertMessage::Math(_) => {}
+                    AssertMessage::Math(_) => {},
+                    AssertMessage::GeneratorResumedAfterReturn => {},
+                    AssertMessage::GeneratorResumedAfterPanic => {},
                 }
             }
 
@@ -553,6 +577,13 @@ macro_rules! make_mir_visitor {
                                 self.visit_def_id(def_id, location);
                                 self.visit_closure_substs(closure_substs, location);
                             }
+                            AggregateKind::Generator(ref $($mutability)* def_id,
+                                                   ref $($mutability)* closure_substs,
+                                                   ref $($mutability)* interior) => {
+                                self.visit_def_id(def_id, location);
+                                self.visit_closure_substs(closure_substs, location);
+                                self.visit_generator_interior(interior, location);
+                            }
                         }
 
                         for operand in operands {
@@ -580,7 +611,8 @@ macro_rules! make_mir_visitor {
                             context: LvalueContext<'tcx>,
                             location: Location) {
                 match *lvalue {
-                    Lvalue::Local(_) => {
+                    Lvalue::Local(ref $($mutability)* local) => {
+                        self.visit_local(local, context, location);
                     }
                     Lvalue::Static(ref $($mutability)* static_) => {
                         self.visit_static(static_, context, location);
@@ -632,8 +664,8 @@ macro_rules! make_mir_visitor {
                     ProjectionElem::Field(_field, ref $($mutability)* ty) => {
                         self.visit_ty(ty, Lookup::Loc(location));
                     }
-                    ProjectionElem::Index(ref $($mutability)* operand) => {
-                        self.visit_operand(operand, location);
+                    ProjectionElem::Index(ref $($mutability)* local) => {
+                        self.visit_local(local, LvalueContext::Consume, location);
                     }
                     ProjectionElem::ConstantIndex { offset: _,
                                                     min_length: _,
@@ -651,6 +683,7 @@ macro_rules! make_mir_visitor {
                     ref $($mutability)* ty,
                     name: _,
                     ref $($mutability)* source_info,
+                    internal: _,
                     is_user_variable: _,
                 } = *local_decl;
 
@@ -719,6 +752,10 @@ macro_rules! make_mir_visitor {
             fn super_substs(&mut self, _substs: & $($mutability)* &'tcx Substs<'tcx>) {
             }
 
+            fn super_generator_interior(&mut self,
+                                    _interior: & $($mutability)* GeneratorInterior<'tcx>) {
+            }
+
             fn super_closure_substs(&mut self,
                                     _substs: & $($mutability)* ClosureSubsts<'tcx>) {
             }
diff --git a/src/librustc/session/config.rs b/src/librustc/session/config.rs
index 99fe8e60ae52b..b538c6a6eca7b 100644
--- a/src/librustc/session/config.rs
+++ b/src/librustc/session/config.rs
@@ -340,6 +340,7 @@ pub enum PrintRequest {
     RelocationModels,
     CodeModels,
     TargetSpec,
+    NativeStaticLibs,
 }
 
 pub enum Input {
@@ -1296,7 +1297,7 @@ pub fn rustc_short_optgroups() -> Vec<RustcOptGroup> {
                                print on stdout",
                      "[crate-name|file-names|sysroot|cfg|target-list|\
                        target-cpus|target-features|relocation-models|\
-                       code-models|target-spec-json]"),
+                       code-models|target-spec-json|native-static-deps]"),
         opt::flagmulti_s("g",  "",  "Equivalent to -C debuginfo=2"),
         opt::flagmulti_s("O", "", "Equivalent to -C opt-level=2"),
         opt::opt_s("o", "", "Write output to <filename>", "FILENAME"),
@@ -1642,6 +1643,7 @@ pub fn build_session_options_and_crate_config(matches: &getopts::Matches)
             "target-features" => PrintRequest::TargetFeatures,
             "relocation-models" => PrintRequest::RelocationModels,
             "code-models" => PrintRequest::CodeModels,
+            "native-static-libs" => PrintRequest::NativeStaticLibs,
             "target-spec-json" => {
                 if nightly_options::is_unstable_enabled(matches) {
                     PrintRequest::TargetSpec
diff --git a/src/librustc/traits/coherence.rs b/src/librustc/traits/coherence.rs
index 34df447a11e15..431bd8ee88f70 100644
--- a/src/librustc/traits/coherence.rs
+++ b/src/librustc/traits/coherence.rs
@@ -301,7 +301,7 @@ fn ty_is_local_constructor(ty: Ty, infer_is_local: InferIsLocal)-> bool {
             true
         }
 
-        ty::TyClosure(..) | ty::TyAnon(..) => {
+        ty::TyClosure(..) | ty::TyGenerator(..) | ty::TyAnon(..) => {
             bug!("ty_is_local invoked on unexpected type: {:?}", ty)
         }
     }
diff --git a/src/librustc/traits/error_reporting.rs b/src/librustc/traits/error_reporting.rs
index 3e64c8c7dea99..ce6da55fec36b 100644
--- a/src/librustc/traits/error_reporting.rs
+++ b/src/librustc/traits/error_reporting.rs
@@ -15,6 +15,8 @@ use super::{
     Obligation,
     ObligationCause,
     ObligationCauseCode,
+    OnUnimplementedDirective,
+    OnUnimplementedNote,
     OutputTypeParameterMismatch,
     TraitNotObjectSafe,
     PredicateObligation,
@@ -25,7 +27,6 @@ use super::{
 };
 
 use errors::DiagnosticBuilder;
-use fmt_macros::{Parser, Piece, Position};
 use hir;
 use hir::def_id::DefId;
 use infer::{self, InferCtxt};
@@ -251,6 +252,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                     AdtKind::Union => Some(16),
                     AdtKind::Enum => Some(17),
                 },
+                ty::TyGenerator(..) => Some(18),
                 ty::TyInfer(..) | ty::TyError => None
             }
         }
@@ -315,77 +317,56 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
         }
     }
 
-    fn on_unimplemented_note(&self,
-                             trait_ref: ty::PolyTraitRef<'tcx>,
-                             obligation: &PredicateObligation<'tcx>) -> Option<String> {
+    fn on_unimplemented_note(
+        &self,
+        trait_ref: ty::PolyTraitRef<'tcx>,
+        obligation: &PredicateObligation<'tcx>) ->
+        OnUnimplementedNote
+    {
         let def_id = self.impl_similar_to(trait_ref, obligation)
             .unwrap_or(trait_ref.def_id());
-        let trait_ref = trait_ref.skip_binder();
+        let trait_ref = *trait_ref.skip_binder();
+
+        let desugaring;
+        let method;
+        let mut flags = vec![];
+        let direct = match obligation.cause.code {
+            ObligationCauseCode::BuiltinDerivedObligation(..) |
+            ObligationCauseCode::ImplDerivedObligation(..) => false,
+            _ => true
+        };
+        if direct {
+            // this is a "direct", user-specified, rather than derived,
+            // obligation.
+            flags.push(("direct", None));
+        }
 
-        let span = obligation.cause.span;
-        let mut report = None;
-        if let Some(item) = self.tcx
-            .get_attrs(def_id)
-            .into_iter()
-            .filter(|a| a.check_name("rustc_on_unimplemented"))
-            .next()
-        {
-            let name = self.tcx.item_name(def_id).as_str();
-            let err_sp = item.span.substitute_dummy(span);
-            let trait_str = self.tcx.item_path_str(trait_ref.def_id);
-            if let Some(istring) = item.value_str() {
-                let istring = &*istring.as_str();
-                let generics = self.tcx.generics_of(trait_ref.def_id);
-                let generic_map = generics.types.iter().map(|param| {
-                    (param.name.as_str().to_string(),
-                        trait_ref.substs.type_for_def(param).to_string())
-                }).collect::<FxHashMap<String, String>>();
-                let parser = Parser::new(istring);
-                let mut errored = false;
-                let err: String = parser.filter_map(|p| {
-                    match p {
-                        Piece::String(s) => Some(s),
-                        Piece::NextArgument(a) => match a.position {
-                            Position::ArgumentNamed(s) => match generic_map.get(s) {
-                                Some(val) => Some(val),
-                                None if s == name => {
-                                    Some(&trait_str)
-                                }
-                                None => {
-                                    span_err!(self.tcx.sess, err_sp, E0272,
-                                              "the #[rustc_on_unimplemented] attribute on trait \
-                                               definition for {} refers to non-existent type \
-                                               parameter {}",
-                                              trait_str, s);
-                                    errored = true;
-                                    None
-                                }
-                            },
-                            _ => {
-                                span_err!(self.tcx.sess, err_sp, E0273,
-                                          "the #[rustc_on_unimplemented] attribute on trait \
-                                           definition for {} must have named format arguments, eg \
-                                           `#[rustc_on_unimplemented = \"foo {{T}}\"]`",
-                                          trait_str);
-                                errored = true;
-                                None
-                            }
-                        }
-                    }
-                }).collect();
-                // Report only if the format string checks out
-                if !errored {
-                    report = Some(err);
-                }
-            } else {
-                span_err!(self.tcx.sess, err_sp, E0274,
-                                        "the #[rustc_on_unimplemented] attribute on \
-                                                    trait definition for {} must have a value, \
-                                                    eg `#[rustc_on_unimplemented = \"foo\"]`",
-                                                    trait_str);
+        if let ObligationCauseCode::ItemObligation(item) = obligation.cause.code {
+            // FIXME: maybe also have some way of handling methods
+            // from other traits? That would require name resolution,
+            // which we might want to be some sort of hygienic.
+            //
+            // Currently I'm leaving it for what I need for `try`.
+            if self.tcx.trait_of_item(item) == Some(trait_ref.def_id) {
+                method = self.tcx.item_name(item).as_str();
+                flags.push(("from_method", None));
+                flags.push(("from_method", Some(&*method)));
             }
         }
-        report
+
+        if let Some(k) = obligation.cause.span.compiler_desugaring_kind() {
+            desugaring = k.as_symbol().as_str();
+            flags.push(("from_desugaring", None));
+            flags.push(("from_desugaring", Some(&*desugaring)));
+        }
+
+        if let Ok(Some(command)) = OnUnimplementedDirective::of_item(
+            self.tcx, trait_ref.def_id, def_id
+        ) {
+            command.evaluate(self.tcx, trait_ref, &flags)
+        } else {
+            OnUnimplementedNote::empty()
+        }
     }
 
     fn find_similar_impl_candidates(&self,
@@ -576,17 +557,23 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                         let (post_message, pre_message) =
                             self.get_parent_trait_ref(&obligation.cause.code)
                                 .map(|t| (format!(" in `{}`", t), format!("within `{}`, ", t)))
-                                .unwrap_or((String::new(), String::new()));
+                            .unwrap_or((String::new(), String::new()));
+
+                        let OnUnimplementedNote { message, label }
+                            = self.on_unimplemented_note(trait_ref, obligation);
+                        let have_alt_message = message.is_some() || label.is_some();
+
                         let mut err = struct_span_err!(
                             self.tcx.sess,
                             span,
                             E0277,
-                            "the trait bound `{}` is not satisfied{}",
-                            trait_ref.to_predicate(),
-                            post_message);
+                            "{}",
+                            message.unwrap_or_else(|| {
+                                format!("the trait bound `{}` is not satisfied{}",
+                                         trait_ref.to_predicate(), post_message)
+                            }));
 
-                        let unimplemented_note = self.on_unimplemented_note(trait_ref, obligation);
-                        if let Some(ref s) = unimplemented_note {
+                        if let Some(ref s) = label {
                             // If it has a custom "#[rustc_on_unimplemented]"
                             // error message, let's display it as the label!
                             err.span_label(span, s.as_str());
@@ -614,7 +601,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                             // which is somewhat confusing.
                             err.help(&format!("consider adding a `where {}` bound",
                                                 trait_ref.to_predicate()));
-                        } else if unimplemented_note.is_none() {
+                        } else if !have_alt_message {
                             // Can't show anything else useful, try to find similar impls.
                             let impl_candidates = self.find_similar_impl_candidates(trait_ref);
                             self.report_similar_impl_candidates(impl_candidates, &mut err);
diff --git a/src/librustc/traits/fulfill.rs b/src/librustc/traits/fulfill.rs
index 78e47693caaf1..fbc393cbd96f2 100644
--- a/src/librustc/traits/fulfill.rs
+++ b/src/librustc/traits/fulfill.rs
@@ -251,6 +251,9 @@ impl<'a, 'gcx, 'tcx> FulfillmentContext<'tcx> {
             });
             debug!("select: outcome={:?}", outcome);
 
+            // FIXME: if we kept the original cache key, we could mark projection
+            // obligations as complete for the projection cache here.
+
             errors.extend(
                 outcome.errors.into_iter()
                               .map(|e| to_fulfillment_error(e)));
diff --git a/src/librustc/traits/mod.rs b/src/librustc/traits/mod.rs
index 5bae82c1a332f..33dcf3c76e6cf 100644
--- a/src/librustc/traits/mod.rs
+++ b/src/librustc/traits/mod.rs
@@ -17,7 +17,7 @@ pub use self::ObligationCauseCode::*;
 
 use hir;
 use hir::def_id::DefId;
-use middle::region::RegionMaps;
+use middle::region;
 use middle::free_region::FreeRegionMap;
 use ty::subst::Substs;
 use ty::{self, AdtKind, Ty, TyCtxt, TypeFoldable, ToPredicate};
@@ -37,8 +37,9 @@ pub use self::project::{normalize, normalize_projection_type, Normalized};
 pub use self::project::{ProjectionCache, ProjectionCacheSnapshot, Reveal};
 pub use self::object_safety::ObjectSafetyViolation;
 pub use self::object_safety::MethodViolationCode;
+pub use self::on_unimplemented::{OnUnimplementedDirective, OnUnimplementedNote};
 pub use self::select::{EvaluationCache, SelectionContext, SelectionCache};
-pub use self::specialize::{OverlapError, specialization_graph, specializes, translate_substs};
+pub use self::specialize::{OverlapError, specialization_graph, translate_substs};
 pub use self::specialize::{SpecializesCache, find_associated_item};
 pub use self::util::elaborate_predicates;
 pub use self::util::supertraits;
@@ -52,6 +53,7 @@ mod error_reporting;
 mod fulfill;
 mod project;
 mod object_safety;
+mod on_unimplemented;
 mod select;
 mod specialize;
 mod structural_impls;
@@ -310,6 +312,9 @@ pub enum Vtable<'tcx, N> {
 
     /// Same as above, but for a fn pointer type with the given signature.
     VtableFnPointer(VtableFnPointerData<'tcx, N>),
+
+    /// Vtable automatically generated for a generator
+    VtableGenerator(VtableGeneratorData<'tcx, N>),
 }
 
 /// Identifies a particular impl in the source, along with a set of
@@ -329,6 +334,15 @@ pub struct VtableImplData<'tcx, N> {
     pub nested: Vec<N>
 }
 
+#[derive(Clone, PartialEq, Eq)]
+pub struct VtableGeneratorData<'tcx, N> {
+    pub closure_def_id: DefId,
+    pub substs: ty::ClosureSubsts<'tcx>,
+    /// Nested obligations. This can be non-empty if the generator
+    /// signature contains associated types.
+    pub nested: Vec<N>
+}
+
 #[derive(Clone, PartialEq, Eq)]
 pub struct VtableClosureData<'tcx, N> {
     pub closure_def_id: DefId,
@@ -520,9 +534,9 @@ pub fn normalize_param_env_or_error<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
         debug!("normalize_param_env_or_error: normalized predicates={:?}",
             predicates);
 
-        let region_maps = RegionMaps::new();
+        let region_scope_tree = region::ScopeTree::default();
         let free_regions = FreeRegionMap::new();
-        infcx.resolve_regions_and_report_errors(region_context, &region_maps, &free_regions);
+        infcx.resolve_regions_and_report_errors(region_context, &region_scope_tree, &free_regions);
         let predicates = match infcx.fully_resolve(&predicates) {
             Ok(predicates) => predicates,
             Err(fixup_err) => {
@@ -743,6 +757,7 @@ impl<'tcx, N> Vtable<'tcx, N> {
             VtableBuiltin(i) => i.nested,
             VtableDefaultImpl(d) => d.nested,
             VtableClosure(c) => c.nested,
+            VtableGenerator(c) => c.nested,
             VtableObject(d) => d.nested,
             VtableFnPointer(d) => d.nested,
         }
@@ -754,6 +769,7 @@ impl<'tcx, N> Vtable<'tcx, N> {
             &mut VtableParam(ref mut n) => n,
             &mut VtableBuiltin(ref mut i) => &mut i.nested,
             &mut VtableDefaultImpl(ref mut d) => &mut d.nested,
+            &mut VtableGenerator(ref mut c) => &mut c.nested,
             &mut VtableClosure(ref mut c) => &mut c.nested,
             &mut VtableObject(ref mut d) => &mut d.nested,
             &mut VtableFnPointer(ref mut d) => &mut d.nested,
@@ -784,6 +800,11 @@ impl<'tcx, N> Vtable<'tcx, N> {
                 fn_ty: p.fn_ty,
                 nested: p.nested.into_iter().map(f).collect(),
             }),
+            VtableGenerator(c) => VtableGenerator(VtableGeneratorData {
+                closure_def_id: c.closure_def_id,
+                substs: c.substs,
+                nested: c.nested.into_iter().map(f).collect(),
+            }),
             VtableClosure(c) => VtableClosure(VtableClosureData {
                 closure_def_id: c.closure_def_id,
                 substs: c.substs,
@@ -812,6 +833,7 @@ pub fn provide(providers: &mut ty::maps::Providers) {
     *providers = ty::maps::Providers {
         is_object_safe: object_safety::is_object_safe_provider,
         specialization_graph_of: specialize::specialization_graph_provider,
+        specializes: specialize::specializes,
         ..*providers
     };
 }
@@ -820,6 +842,7 @@ pub fn provide_extern(providers: &mut ty::maps::Providers) {
     *providers = ty::maps::Providers {
         is_object_safe: object_safety::is_object_safe_provider,
         specialization_graph_of: specialize::specialization_graph_provider,
+        specializes: specialize::specializes,
         ..*providers
     };
 }
diff --git a/src/librustc/traits/on_unimplemented.rs b/src/librustc/traits/on_unimplemented.rs
new file mode 100644
index 0000000000000..7dd3fc70b1e3f
--- /dev/null
+++ b/src/librustc/traits/on_unimplemented.rs
@@ -0,0 +1,307 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use fmt_macros::{Parser, Piece, Position};
+
+use hir::def_id::DefId;
+use ty::{self, TyCtxt};
+use util::common::ErrorReported;
+use util::nodemap::FxHashMap;
+
+use syntax::ast::{MetaItem, NestedMetaItem};
+use syntax::attr;
+use syntax_pos::Span;
+use syntax_pos::symbol::InternedString;
+
+#[derive(Clone, Debug)]
+pub struct OnUnimplementedFormatString(InternedString);
+
+#[derive(Debug)]
+pub struct OnUnimplementedDirective {
+    pub condition: Option<MetaItem>,
+    pub subcommands: Vec<OnUnimplementedDirective>,
+    pub message: Option<OnUnimplementedFormatString>,
+    pub label: Option<OnUnimplementedFormatString>,
+}
+
+pub struct OnUnimplementedNote {
+    pub message: Option<String>,
+    pub label: Option<String>,
+}
+
+impl OnUnimplementedNote {
+    pub fn empty() -> Self {
+        OnUnimplementedNote { message: None, label: None }
+    }
+}
+
+fn parse_error(tcx: TyCtxt, span: Span,
+               message: &str,
+               label: &str,
+               note: Option<&str>)
+               -> ErrorReported
+{
+    let mut diag = struct_span_err!(
+        tcx.sess, span, E0232, "{}", message);
+    diag.span_label(span, label);
+    if let Some(note) = note {
+        diag.note(note);
+    }
+    diag.emit();
+    ErrorReported
+}
+
+impl<'a, 'gcx, 'tcx> OnUnimplementedDirective {
+    pub fn parse(tcx: TyCtxt<'a, 'gcx, 'tcx>,
+                 trait_def_id: DefId,
+                 items: &[NestedMetaItem],
+                 span: Span,
+                 is_root: bool)
+                 -> Result<Self, ErrorReported>
+    {
+        let mut errored = false;
+        let mut item_iter = items.iter();
+
+        let condition = if is_root {
+            None
+        } else {
+            let cond = item_iter.next().ok_or_else(|| {
+                parse_error(tcx, span,
+                            "empty `on`-clause in `#[rustc_on_unimplemented]`",
+                            "empty on-clause here",
+                            None)
+            })?.meta_item().ok_or_else(|| {
+                parse_error(tcx, span,
+                            "invalid `on`-clause in `#[rustc_on_unimplemented]`",
+                            "invalid on-clause here",
+                            None)
+            })?;
+            attr::eval_condition(cond, &tcx.sess.parse_sess, &mut |_| true);
+            Some(cond.clone())
+        };
+
+        let mut message = None;
+        let mut label = None;
+        let mut subcommands = vec![];
+        for item in item_iter {
+            if item.check_name("message") && message.is_none() {
+                if let Some(message_) = item.value_str() {
+                    message = Some(OnUnimplementedFormatString::try_parse(
+                        tcx, trait_def_id, message_.as_str(), span)?);
+                    continue;
+                }
+            } else if item.check_name("label") && label.is_none() {
+                if let Some(label_) = item.value_str() {
+                    label = Some(OnUnimplementedFormatString::try_parse(
+                        tcx, trait_def_id, label_.as_str(), span)?);
+                    continue;
+                }
+            } else if item.check_name("on") && is_root &&
+                message.is_none() && label.is_none()
+            {
+                if let Some(items) = item.meta_item_list() {
+                    if let Ok(subcommand) =
+                        Self::parse(tcx, trait_def_id, &items, item.span, false)
+                    {
+                        subcommands.push(subcommand);
+                    } else {
+                        errored = true;
+                    }
+                    continue
+                }
+            }
+
+            // nothing found
+            parse_error(tcx, item.span,
+                        "this attribute must have a valid value",
+                        "expected value here",
+                        Some(r#"eg `#[rustc_on_unimplemented = "foo"]`"#));
+        }
+
+        if errored {
+            Err(ErrorReported)
+        } else {
+            Ok(OnUnimplementedDirective { condition, message, label, subcommands })
+        }
+    }
+
+
+    pub fn of_item(tcx: TyCtxt<'a, 'gcx, 'tcx>,
+                   trait_def_id: DefId,
+                   impl_def_id: DefId)
+                   -> Result<Option<Self>, ErrorReported>
+    {
+        let attrs = tcx.get_attrs(impl_def_id);
+
+        let attr = if let Some(item) =
+            attrs.into_iter().find(|a| a.check_name("rustc_on_unimplemented"))
+        {
+            item
+        } else {
+            return Ok(None);
+        };
+
+        let result = if let Some(items) = attr.meta_item_list() {
+            Self::parse(tcx, trait_def_id, &items, attr.span, true).map(Some)
+        } else if let Some(value) = attr.value_str() {
+            Ok(Some(OnUnimplementedDirective {
+                condition: None,
+                message: None,
+                subcommands: vec![],
+                label: Some(OnUnimplementedFormatString::try_parse(
+                    tcx, trait_def_id, value.as_str(), attr.span)?)
+            }))
+        } else {
+            return Err(parse_error(tcx, attr.span,
+                                   "`#[rustc_on_unimplemented]` requires a value",
+                                   "value required here",
+                                   Some(r#"eg `#[rustc_on_unimplemented = "foo"]`"#)));
+        };
+        debug!("of_item({:?}/{:?}) = {:?}", trait_def_id, impl_def_id, result);
+        result
+    }
+
+    pub fn evaluate(&self,
+                    tcx: TyCtxt<'a, 'gcx, 'tcx>,
+                    trait_ref: ty::TraitRef<'tcx>,
+                    options: &[(&str, Option<&str>)])
+                    -> OnUnimplementedNote
+    {
+        let mut message = None;
+        let mut label = None;
+        info!("evaluate({:?}, trait_ref={:?}, options={:?})",
+              self, trait_ref, options);
+
+        for command in self.subcommands.iter().chain(Some(self)).rev() {
+            if let Some(ref condition) = command.condition {
+                if !attr::eval_condition(condition, &tcx.sess.parse_sess, &mut |c| {
+                    options.contains(&(&c.name().as_str(),
+                                      match c.value_str().map(|s| s.as_str()) {
+                                          Some(ref s) => Some(s),
+                                          None => None
+                                      }))
+                }) {
+                    debug!("evaluate: skipping {:?} due to condition", command);
+                    continue
+                }
+            }
+            debug!("evaluate: {:?} succeeded", command);
+            if let Some(ref message_) = command.message {
+                message = Some(message_.clone());
+            }
+
+            if let Some(ref label_) = command.label {
+                label = Some(label_.clone());
+            }
+        }
+
+        OnUnimplementedNote {
+            label: label.map(|l| l.format(tcx, trait_ref)),
+            message: message.map(|m| m.format(tcx, trait_ref))
+        }
+    }
+}
+
+impl<'a, 'gcx, 'tcx> OnUnimplementedFormatString {
+    pub fn try_parse(tcx: TyCtxt<'a, 'gcx, 'tcx>,
+                     trait_def_id: DefId,
+                     from: InternedString,
+                     err_sp: Span)
+                     -> Result<Self, ErrorReported>
+    {
+        let result = OnUnimplementedFormatString(from);
+        result.verify(tcx, trait_def_id, err_sp)?;
+        Ok(result)
+    }
+
+    fn verify(&self,
+              tcx: TyCtxt<'a, 'gcx, 'tcx>,
+              trait_def_id: DefId,
+              span: Span)
+              -> Result<(), ErrorReported>
+    {
+        let name = tcx.item_name(trait_def_id).as_str();
+        let generics = tcx.generics_of(trait_def_id);
+        let parser = Parser::new(&self.0);
+        let types = &generics.types;
+        let mut result = Ok(());
+        for token in parser {
+            match token {
+                Piece::String(_) => (), // Normal string, no need to check it
+                Piece::NextArgument(a) => match a.position {
+                    // `{Self}` is allowed
+                    Position::ArgumentNamed(s) if s == "Self" => (),
+                    // `{ThisTraitsName}` is allowed
+                    Position::ArgumentNamed(s) if s == name => (),
+                    // So is `{A}` if A is a type parameter
+                    Position::ArgumentNamed(s) => match types.iter().find(|t| {
+                        t.name == s
+                    }) {
+                        Some(_) => (),
+                        None => {
+                            span_err!(tcx.sess, span, E0230,
+                                      "there is no type parameter \
+                                       {} on trait {}",
+                                      s, name);
+                            result = Err(ErrorReported);
+                        }
+                    },
+                    // `{:1}` and `{}` are not to be used
+                    Position::ArgumentIs(_) => {
+                        span_err!(tcx.sess, span, E0231,
+                                  "only named substitution \
+                                   parameters are allowed");
+                        result = Err(ErrorReported);
+                    }
+                }
+            }
+        }
+
+        result
+    }
+
+    pub fn format(&self,
+                  tcx: TyCtxt<'a, 'gcx, 'tcx>,
+                  trait_ref: ty::TraitRef<'tcx>)
+                  -> String
+    {
+        let name = tcx.item_name(trait_ref.def_id).as_str();
+        let trait_str = tcx.item_path_str(trait_ref.def_id);
+        let generics = tcx.generics_of(trait_ref.def_id);
+        let generic_map = generics.types.iter().map(|param| {
+            (param.name.as_str().to_string(),
+             trait_ref.substs.type_for_def(param).to_string())
+        }).collect::<FxHashMap<String, String>>();
+
+        let parser = Parser::new(&self.0);
+        parser.map(|p| {
+            match p {
+                Piece::String(s) => s,
+                Piece::NextArgument(a) => match a.position {
+                    Position::ArgumentNamed(s) => match generic_map.get(s) {
+                        Some(val) => val,
+                        None if s == name => {
+                            &trait_str
+                        }
+                        None => {
+                            bug!("broken on_unimplemented {:?} for {:?}: \
+                                  no argument matching {:?}",
+                                 self.0, trait_ref, s)
+                        }
+                    },
+                    _ => {
+                        bug!("broken on_unimplemented {:?} - bad \
+                              format arg", self.0)
+                    }
+                }
+            }
+        }).collect()
+    }
+}
diff --git a/src/librustc/traits/project.rs b/src/librustc/traits/project.rs
index e70258007e463..512cfee12b05f 100644
--- a/src/librustc/traits/project.rs
+++ b/src/librustc/traits/project.rs
@@ -19,6 +19,7 @@ use super::PredicateObligation;
 use super::SelectionContext;
 use super::SelectionError;
 use super::VtableClosureData;
+use super::VtableGeneratorData;
 use super::VtableFnPointerData;
 use super::VtableImplData;
 use super::util;
@@ -121,11 +122,13 @@ struct ProjectionTyCandidateSet<'tcx> {
 ///
 ///     for<...> <T as Trait>::U == V
 ///
-/// If successful, this may result in additional obligations.
+/// If successful, this may result in additional obligations. Also returns
+/// the projection cache key used to track these additional obligations.
 pub fn poly_project_and_unify_type<'cx, 'gcx, 'tcx>(
     selcx: &mut SelectionContext<'cx, 'gcx, 'tcx>,
     obligation: &PolyProjectionObligation<'tcx>)
-    -> Result<Option<Vec<PredicateObligation<'tcx>>>, MismatchedProjectionTypes<'tcx>>
+    -> Result<Option<Vec<PredicateObligation<'tcx>>>,
+              MismatchedProjectionTypes<'tcx>>
 {
     debug!("poly_project_and_unify_type(obligation={:?})",
            obligation);
@@ -161,7 +164,8 @@ pub fn poly_project_and_unify_type<'cx, 'gcx, 'tcx>(
 fn project_and_unify_type<'cx, 'gcx, 'tcx>(
     selcx: &mut SelectionContext<'cx, 'gcx, 'tcx>,
     obligation: &ProjectionObligation<'tcx>)
-    -> Result<Option<Vec<PredicateObligation<'tcx>>>, MismatchedProjectionTypes<'tcx>>
+    -> Result<Option<Vec<PredicateObligation<'tcx>>>,
+              MismatchedProjectionTypes<'tcx>>
 {
     debug!("project_and_unify_type(obligation={:?})",
            obligation);
@@ -396,6 +400,7 @@ fn opt_normalize_projection_type<'a, 'b, 'gcx, 'tcx>(
     let infcx = selcx.infcx();
 
     let projection_ty = infcx.resolve_type_vars_if_possible(&projection_ty);
+    let cache_key = ProjectionCacheKey { ty: projection_ty };
 
     debug!("opt_normalize_projection_type(\
            projection_ty={:?}, \
@@ -411,7 +416,7 @@ fn opt_normalize_projection_type<'a, 'b, 'gcx, 'tcx>(
     // bounds. It might be the case that we want two distinct caches,
     // or else another kind of cache entry.
 
-    match infcx.projection_cache.borrow_mut().try_start(projection_ty) {
+    match infcx.projection_cache.borrow_mut().try_start(cache_key) {
         Ok(()) => { }
         Err(ProjectionCacheEntry::Ambiguous) => {
             // If we found ambiguity the last time, that generally
@@ -522,7 +527,7 @@ fn opt_normalize_projection_type<'a, 'b, 'gcx, 'tcx>(
                     obligations,
                 }
             };
-            infcx.projection_cache.borrow_mut().complete(projection_ty, &result);
+            infcx.projection_cache.borrow_mut().insert_ty(cache_key, &result);
             Some(result)
         }
         Ok(ProjectedTy::NoProgress(projected_ty)) => {
@@ -533,14 +538,14 @@ fn opt_normalize_projection_type<'a, 'b, 'gcx, 'tcx>(
                 value: projected_ty,
                 obligations: vec![]
             };
-            infcx.projection_cache.borrow_mut().complete(projection_ty, &result);
+            infcx.projection_cache.borrow_mut().insert_ty(cache_key, &result);
             Some(result)
         }
         Err(ProjectionTyError::TooManyCandidates) => {
             debug!("opt_normalize_projection_type: \
                     too many candidates");
             infcx.projection_cache.borrow_mut()
-                                  .ambiguous(projection_ty);
+                                  .ambiguous(cache_key);
             None
         }
         Err(ProjectionTyError::TraitSelectionError(_)) => {
@@ -551,7 +556,7 @@ fn opt_normalize_projection_type<'a, 'b, 'gcx, 'tcx>(
             // reported later
 
             infcx.projection_cache.borrow_mut()
-                                  .error(projection_ty);
+                                  .error(cache_key);
             Some(normalize_to_error(selcx, param_env, projection_ty, cause, depth))
         }
     }
@@ -882,6 +887,7 @@ fn assemble_candidates_from_impls<'cx, 'gcx, 'tcx>(
 
         match vtable {
             super::VtableClosure(_) |
+            super::VtableGenerator(_) |
             super::VtableFnPointer(_) |
             super::VtableObject(_) => {
                 debug!("assemble_candidates_from_impls: vtable={:?}",
@@ -1041,6 +1047,8 @@ fn confirm_select_candidate<'cx, 'gcx, 'tcx>(
     match vtable {
         super::VtableImpl(data) =>
             confirm_impl_candidate(selcx, obligation, data),
+        super::VtableGenerator(data) =>
+            confirm_generator_candidate(selcx, obligation, data),
         super::VtableClosure(data) =>
             confirm_closure_candidate(selcx, obligation, data),
         super::VtableFnPointer(data) =>
@@ -1123,6 +1131,60 @@ fn confirm_object_candidate<'cx, 'gcx, 'tcx>(
     confirm_param_env_candidate(selcx, obligation, env_predicate)
 }
 
+fn confirm_generator_candidate<'cx, 'gcx, 'tcx>(
+    selcx: &mut SelectionContext<'cx, 'gcx, 'tcx>,
+    obligation: &ProjectionTyObligation<'tcx>,
+    vtable: VtableGeneratorData<'tcx, PredicateObligation<'tcx>>)
+    -> Progress<'tcx>
+{
+    let gen_sig = selcx.infcx().generator_sig(vtable.closure_def_id).unwrap()
+        .subst(selcx.tcx(), vtable.substs.substs);
+    let Normalized {
+        value: gen_sig,
+        obligations
+    } = normalize_with_depth(selcx,
+                             obligation.param_env,
+                             obligation.cause.clone(),
+                             obligation.recursion_depth+1,
+                             &gen_sig);
+
+    debug!("confirm_generator_candidate: obligation={:?},gen_sig={:?},obligations={:?}",
+           obligation,
+           gen_sig,
+           obligations);
+
+    let tcx = selcx.tcx();
+
+    let gen_def_id = tcx.lang_items.gen_trait().unwrap();
+
+    // Note: we unwrap the binder here but re-create it below (1)
+    let ty::Binder((trait_ref, yield_ty, return_ty)) =
+        tcx.generator_trait_ref_and_outputs(gen_def_id,
+                                            obligation.predicate.self_ty(),
+                                            gen_sig);
+
+    let name = tcx.associated_item(obligation.predicate.item_def_id).name;
+    let ty = if name == Symbol::intern("Return") {
+        return_ty
+    } else if name == Symbol::intern("Yield") {
+        yield_ty
+    } else {
+        bug!()
+    };
+
+    let predicate = ty::Binder(ty::ProjectionPredicate { // (1) recreate binder here
+        projection_ty: ty::ProjectionTy {
+            substs: trait_ref.substs,
+            item_def_id: obligation.predicate.item_def_id,
+        },
+        ty: ty
+    });
+
+    confirm_param_env_candidate(selcx, obligation, predicate)
+        .with_addl_obligations(vtable.nested)
+        .with_addl_obligations(obligations)
+}
+
 fn confirm_fn_pointer_candidate<'cx, 'gcx, 'tcx>(
     selcx: &mut SelectionContext<'cx, 'gcx, 'tcx>,
     obligation: &ProjectionTyObligation<'tcx>,
@@ -1323,8 +1385,62 @@ fn assoc_ty_def<'cx, 'gcx, 'tcx>(
 
 // # Cache
 
+/// The projection cache. Unlike the standard caches, this can
+/// include infcx-dependent type variables - therefore, we have to roll
+/// the cache back each time we roll a snapshot back, to avoid assumptions
+/// on yet-unresolved inference variables. Types with skolemized regions
+/// also have to be removed when the respective snapshot ends.
+///
+/// Because of that, projection cache entries can be "stranded" and left
+/// inaccessible when type variables inside the key are resolved. We make no
+/// attempt to recover or remove "stranded" entries, but rather let them be
+/// (for the lifetime of the infcx).
+///
+/// Entries in the projection cache might contain inference variables
+/// that will be resolved by obligations on the projection cache entry - e.g.
+/// when a type parameter in the associated type is constrained through
+/// an "RFC 447" projection on the impl.
+///
+/// When working with a fulfillment context, the derived obligations of each
+/// projection cache entry will be registered on the fulfillcx, so any users
+/// that can wait for a fulfillcx fixed point need not care about this. However,
+/// users that don't wait for a fixed point (e.g. trait evaluation) have to
+/// resolve the obligations themselves to make sure the projected result is
+/// ok and avoid issues like #43132.
+///
+/// If that is done, after evaluation the obligations, it is a good idea to
+/// call `ProjectionCache::complete` to make sure the obligations won't be
+/// re-evaluated and avoid an exponential worst-case.
+///
+/// FIXME: we probably also want some sort of cross-infcx cache here to
+/// reduce the amount of duplication. Let's see what we get with the Chalk
+/// reforms.
 pub struct ProjectionCache<'tcx> {
-    map: SnapshotMap<ty::ProjectionTy<'tcx>, ProjectionCacheEntry<'tcx>>,
+    map: SnapshotMap<ProjectionCacheKey<'tcx>, ProjectionCacheEntry<'tcx>>,
+}
+
+#[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)]
+pub struct ProjectionCacheKey<'tcx> {
+    ty: ty::ProjectionTy<'tcx>
+}
+
+impl<'cx, 'gcx, 'tcx> ProjectionCacheKey<'tcx> {
+    pub fn from_poly_projection_predicate(selcx: &mut SelectionContext<'cx, 'gcx, 'tcx>,
+                                          predicate: &ty::PolyProjectionPredicate<'tcx>)
+                                          -> Option<Self>
+    {
+        let infcx = selcx.infcx();
+        // We don't do cross-snapshot caching of obligations with escaping regions,
+        // so there's no cache key to use
+        infcx.tcx.no_late_bound_regions(&predicate)
+            .map(|predicate| ProjectionCacheKey {
+                // We don't attempt to match up with a specific type-variable state
+                // from a specific call to `opt_normalize_projection_type` - if
+                // there's no precise match, the original cache entry is "stranded"
+                // anyway.
+                ty: infcx.resolve_type_vars_if_possible(&predicate.projection_ty)
+            })
+    }
 }
 
 #[derive(Clone, Debug)]
@@ -1337,7 +1453,7 @@ enum ProjectionCacheEntry<'tcx> {
 
 // NB: intentionally not Clone
 pub struct ProjectionCacheSnapshot {
-    snapshot: Snapshot
+    snapshot: Snapshot,
 }
 
 impl<'tcx> ProjectionCache<'tcx> {
@@ -1356,7 +1472,7 @@ impl<'tcx> ProjectionCache<'tcx> {
     }
 
     pub fn rollback_skolemized(&mut self, snapshot: &ProjectionCacheSnapshot) {
-        self.map.partial_rollback(&snapshot.snapshot, &|k| k.has_re_skol());
+        self.map.partial_rollback(&snapshot.snapshot, &|k| k.ty.has_re_skol());
     }
 
     pub fn commit(&mut self, snapshot: ProjectionCacheSnapshot) {
@@ -1366,7 +1482,7 @@ impl<'tcx> ProjectionCache<'tcx> {
     /// Try to start normalize `key`; returns an error if
     /// normalization already occurred (this error corresponds to a
     /// cache hit, so it's actually a good thing).
-    fn try_start(&mut self, key: ty::ProjectionTy<'tcx>)
+    fn try_start(&mut self, key: ProjectionCacheKey<'tcx>)
                  -> Result<(), ProjectionCacheEntry<'tcx>> {
         if let Some(entry) = self.map.get(&key) {
             return Err(entry.clone());
@@ -1377,25 +1493,51 @@ impl<'tcx> ProjectionCache<'tcx> {
     }
 
     /// Indicates that `key` was normalized to `value`.
-    fn complete(&mut self, key: ty::ProjectionTy<'tcx>, value: &NormalizedTy<'tcx>) {
-        debug!("ProjectionCacheEntry::complete: adding cache entry: key={:?}, value={:?}",
+    fn insert_ty(&mut self, key: ProjectionCacheKey<'tcx>, value: &NormalizedTy<'tcx>) {
+        debug!("ProjectionCacheEntry::insert_ty: adding cache entry: key={:?}, value={:?}",
                key, value);
         let fresh_key = self.map.insert(key, ProjectionCacheEntry::NormalizedTy(value.clone()));
         assert!(!fresh_key, "never started projecting `{:?}`", key);
     }
 
+    /// Mark the relevant projection cache key as having its derived obligations
+    /// complete, so they won't have to be re-computed (this is OK to do in a
+    /// snapshot - if the snapshot is rolled back, the obligations will be
+    /// marked as incomplete again).
+    pub fn complete(&mut self, key: ProjectionCacheKey<'tcx>) {
+        let ty = match self.map.get(&key) {
+            Some(&ProjectionCacheEntry::NormalizedTy(ref ty)) => {
+                debug!("ProjectionCacheEntry::complete({:?}) - completing {:?}",
+                       key, ty);
+                ty.value
+            }
+            ref value => {
+                // Type inference could "strand behind" old cache entries. Leave
+                // them alone for now.
+                debug!("ProjectionCacheEntry::complete({:?}) - ignoring {:?}",
+                       key, value);
+                return
+            }
+        };
+
+        self.map.insert(key, ProjectionCacheEntry::NormalizedTy(Normalized {
+            value: ty,
+            obligations: vec![]
+        }));
+    }
+
     /// Indicates that trying to normalize `key` resulted in
     /// ambiguity. No point in trying it again then until we gain more
     /// type information (in which case, the "fully resolved" key will
     /// be different).
-    fn ambiguous(&mut self, key: ty::ProjectionTy<'tcx>) {
+    fn ambiguous(&mut self, key: ProjectionCacheKey<'tcx>) {
         let fresh = self.map.insert(key, ProjectionCacheEntry::Ambiguous);
         assert!(!fresh, "never started projecting `{:?}`", key);
     }
 
     /// Indicates that trying to normalize `key` resulted in
     /// error.
-    fn error(&mut self, key: ty::ProjectionTy<'tcx>) {
+    fn error(&mut self, key: ProjectionCacheKey<'tcx>) {
         let fresh = self.map.insert(key, ProjectionCacheEntry::Error);
         assert!(!fresh, "never started projecting `{:?}`", key);
     }
diff --git a/src/librustc/traits/select.rs b/src/librustc/traits/select.rs
index 46bdb1344b2fe..726e5d83428ca 100644
--- a/src/librustc/traits/select.rs
+++ b/src/librustc/traits/select.rs
@@ -16,7 +16,7 @@ use self::EvaluationResult::*;
 use super::coherence;
 use super::DerivedObligationCause;
 use super::project;
-use super::project::{normalize_with_depth, Normalized};
+use super::project::{normalize_with_depth, Normalized, ProjectionCacheKey};
 use super::{PredicateObligation, TraitObligation, ObligationCause};
 use super::{ObligationCauseCode, BuiltinDerivedObligation, ImplDerivedObligation};
 use super::{SelectionError, Unimplemented, OutputTypeParameterMismatch};
@@ -24,9 +24,9 @@ use super::{ObjectCastObligation, Obligation};
 use super::TraitNotObjectSafe;
 use super::Selection;
 use super::SelectionResult;
-use super::{VtableBuiltin, VtableImpl, VtableParam, VtableClosure,
+use super::{VtableBuiltin, VtableImpl, VtableParam, VtableClosure, VtableGenerator,
             VtableFnPointer, VtableObject, VtableDefaultImpl};
-use super::{VtableImplData, VtableObjectData, VtableBuiltinData,
+use super::{VtableImplData, VtableObjectData, VtableBuiltinData, VtableGeneratorData,
             VtableClosureData, VtableDefaultImplData, VtableFnPointerData};
 use super::util;
 
@@ -36,13 +36,13 @@ use infer;
 use infer::{InferCtxt, InferOk, TypeFreshener};
 use ty::subst::{Kind, Subst, Substs};
 use ty::{self, ToPredicate, ToPolyTraitRef, Ty, TyCtxt, TypeFoldable};
-use traits;
 use ty::fast_reject;
 use ty::relate::TypeRelation;
 use middle::lang_items;
 
 use rustc_data_structures::bitvec::BitVector;
 use rustc_data_structures::snapshot_vec::{SnapshotVecDelegate, SnapshotVec};
+use std::iter;
 use std::cell::RefCell;
 use std::cmp;
 use std::fmt;
@@ -193,9 +193,12 @@ enum SelectionCandidate<'tcx> {
     ProjectionCandidate,
 
     /// Implementation of a `Fn`-family trait by one of the anonymous types
-    /// generated for a `||` expression. The ty::ClosureKind informs the
-    /// confirmation step what ClosureKind obligation to emit.
-    ClosureCandidate(/* closure */ DefId, ty::ClosureSubsts<'tcx>, ty::ClosureKind),
+    /// generated for a `||` expression.
+    ClosureCandidate,
+
+    /// Implementation of a `Generator` trait by one of the anonymous types
+    /// generated for a generator.
+    GeneratorCandidate,
 
     /// Implementation of a `Fn`-family trait by one of the anonymous
     /// types generated for a fn pointer type (e.g., `fn(int)->int`)
@@ -224,15 +227,12 @@ impl<'a, 'tcx> ty::Lift<'tcx> for SelectionCandidate<'a> {
             ObjectCandidate => ObjectCandidate,
             BuiltinObjectCandidate => BuiltinObjectCandidate,
             BuiltinUnsizeCandidate => BuiltinUnsizeCandidate,
+            ClosureCandidate => ClosureCandidate,
+            GeneratorCandidate => GeneratorCandidate,
 
             ParamCandidate(ref trait_ref) => {
                 return tcx.lift(trait_ref).map(ParamCandidate);
             }
-            ClosureCandidate(def_id, ref substs, kind) => {
-                return tcx.lift(substs).map(|substs| {
-                    ClosureCandidate(def_id, substs, kind)
-                });
-            }
         })
     }
 }
@@ -655,8 +655,14 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
                 let project_obligation = obligation.with(data.clone());
                 match project::poly_project_and_unify_type(self, &project_obligation) {
                     Ok(Some(subobligations)) => {
-                        self.evaluate_predicates_recursively(previous_stack,
-                                                             subobligations.iter())
+                        let result = self.evaluate_predicates_recursively(previous_stack,
+                                                                          subobligations.iter());
+                        if let Some(key) =
+                            ProjectionCacheKey::from_poly_projection_predicate(self, data)
+                        {
+                            self.infcx.projection_cache.borrow_mut().complete(key);
+                        }
+                        result
                     }
                     Ok(None) => {
                         EvaluatedToAmbig
@@ -888,14 +894,9 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
                                dep_node: DepNodeIndex,
                                result: EvaluationResult)
     {
-        // Avoid caching results that depend on more than just the trait-ref:
-        // The stack can create recursion, and closure signatures
-        // being yet uninferred can create "spurious" EvaluatedToAmbig
-        // and EvaluatedToOk.
-        if result.is_stack_dependent() ||
-            ((result == EvaluatedToAmbig || result == EvaluatedToOk)
-             && trait_ref.has_closure_types())
-        {
+        // Avoid caching results that depend on more than just the trait-ref
+        // - the stack can create recursion.
+        if result.is_stack_dependent() {
             return;
         }
 
@@ -955,15 +956,12 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
             this.candidate_from_obligation_no_cache(stack)
         });
 
-        if self.should_update_candidate_cache(&cache_fresh_trait_pred, &candidate) {
-            debug!("CACHE MISS: SELECT({:?})={:?}",
-                   cache_fresh_trait_pred, candidate);
-            self.insert_candidate_cache(stack.obligation.param_env,
-                                        cache_fresh_trait_pred,
-                                        dep_node,
-                                        candidate.clone());
-        }
-
+        debug!("CACHE MISS: SELECT({:?})={:?}",
+               cache_fresh_trait_pred, candidate);
+        self.insert_candidate_cache(stack.obligation.param_env,
+                                    cache_fresh_trait_pred,
+                                    dep_node,
+                                    candidate.clone());
         candidate
     }
 
@@ -1203,45 +1201,6 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
                                   .insert(trait_ref, WithDepNode::new(dep_node, candidate));
     }
 
-    fn should_update_candidate_cache(&mut self,
-                                     cache_fresh_trait_pred: &ty::PolyTraitPredicate<'tcx>,
-                                     candidate: &SelectionResult<'tcx, SelectionCandidate<'tcx>>)
-                                     -> bool
-    {
-        // In general, it's a good idea to cache results, even
-        // ambiguous ones, to save us some trouble later. But we have
-        // to be careful not to cache results that could be
-        // invalidated later by advances in inference. Normally, this
-        // is not an issue, because any inference variables whose
-        // types are not yet bound are "freshened" in the cache key,
-        // which means that if we later get the same request once that
-        // type variable IS bound, we'll have a different cache key.
-        // For example, if we have `Vec<_#0t> : Foo`, and `_#0t` is
-        // not yet known, we may cache the result as `None`. But if
-        // later `_#0t` is bound to `Bar`, then when we freshen we'll
-        // have `Vec<Bar> : Foo` as the cache key.
-        //
-        // HOWEVER, it CAN happen that we get an ambiguity result in
-        // one particular case around closures where the cache key
-        // would not change. That is when the precise types of the
-        // upvars that a closure references have not yet been figured
-        // out (i.e., because it is not yet known if they are captured
-        // by ref, and if by ref, what kind of ref). In these cases,
-        // when matching a builtin bound, we will yield back an
-        // ambiguous result. But the *cache key* is just the closure type,
-        // it doesn't capture the state of the upvar computation.
-        //
-        // To avoid this trap, just don't cache ambiguous results if
-        // the self-type contains no inference byproducts (that really
-        // shouldn't happen in other circumstances anyway, given
-        // coherence).
-
-        match *candidate {
-            Ok(Some(_)) | Err(_) => true,
-            Ok(None) => cache_fresh_trait_pred.has_infer_types()
-        }
-    }
-
     fn assemble_candidates<'o>(&mut self,
                                stack: &TraitObligationStack<'o, 'tcx>)
                                -> Result<SelectionCandidateSet<'tcx>, SelectionError<'tcx>>
@@ -1296,14 +1255,15 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
          } else if self.tcx().lang_items.unsize_trait() == Some(def_id) {
              self.assemble_candidates_for_unsizing(obligation, &mut candidates);
          } else {
-            if self.tcx().lang_items.clone_trait() == Some(def_id) {
-                // Same builtin conditions as `Copy`, i.e. every type which has builtin support
-                // for `Copy` also has builtin support for `Clone`, + tuples and arrays of `Clone`
-                // types have builtin support for `Clone`.
-                let clone_conditions = self.copy_conditions(obligation);
-                self.assemble_builtin_bound_candidates(clone_conditions, &mut candidates)?;
-            }
-
+             if self.tcx().lang_items.clone_trait() == Some(def_id) {
+                 // Same builtin conditions as `Copy`, i.e. every type which has builtin support
+                 // for `Copy` also has builtin support for `Clone`, + tuples and arrays of `Clone`
+                 // types have builtin support for `Clone`.
+                 let clone_conditions = self.copy_conditions(obligation);
+                 self.assemble_builtin_bound_candidates(clone_conditions, &mut candidates)?;
+             }
+
+             self.assemble_generator_candidates(obligation, &mut candidates)?;
              self.assemble_closure_candidates(obligation, &mut candidates)?;
              self.assemble_fn_pointer_candidates(obligation, &mut candidates)?;
              self.assemble_candidates_from_impls(obligation, &mut candidates)?;
@@ -1488,6 +1448,37 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
         })
     }
 
+    fn assemble_generator_candidates(&mut self,
+                                   obligation: &TraitObligation<'tcx>,
+                                   candidates: &mut SelectionCandidateSet<'tcx>)
+                                   -> Result<(),SelectionError<'tcx>>
+    {
+        if self.tcx().lang_items.gen_trait() != Some(obligation.predicate.def_id()) {
+            return Ok(());
+        }
+
+        // ok to skip binder because the substs on generator types never
+        // touch bound regions, they just capture the in-scope
+        // type/region parameters
+        let self_ty = *obligation.self_ty().skip_binder();
+        match self_ty.sty {
+            ty::TyGenerator(..) => {
+                debug!("assemble_generator_candidates: self_ty={:?} obligation={:?}",
+                       self_ty,
+                       obligation);
+
+                candidates.vec.push(GeneratorCandidate);
+                Ok(())
+            }
+            ty::TyInfer(ty::TyVar(_)) => {
+                debug!("assemble_generator_candidates: ambiguous self-type");
+                candidates.ambiguous = true;
+                return Ok(());
+            }
+            _ => { return Ok(()); }
+        }
+    }
+
     /// Check for the artificial impl that the compiler will create for an obligation like `X :
     /// FnMut<..>` where `X` is a closure type.
     ///
@@ -1507,36 +1498,31 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
         // ok to skip binder because the substs on closure types never
         // touch bound regions, they just capture the in-scope
         // type/region parameters
-        let self_ty = *obligation.self_ty().skip_binder();
-        let (closure_def_id, substs) = match self_ty.sty {
-            ty::TyClosure(id, substs) => (id, substs),
+        match obligation.self_ty().skip_binder().sty {
+            ty::TyClosure(closure_def_id, _) => {
+                debug!("assemble_unboxed_candidates: kind={:?} obligation={:?}",
+                       kind, obligation);
+                match self.infcx.closure_kind(closure_def_id) {
+                    Some(closure_kind) => {
+                        debug!("assemble_unboxed_candidates: closure_kind = {:?}", closure_kind);
+                        if closure_kind.extends(kind) {
+                            candidates.vec.push(ClosureCandidate);
+                        }
+                    }
+                    None => {
+                        debug!("assemble_unboxed_candidates: closure_kind not yet known");
+                        candidates.vec.push(ClosureCandidate);
+                    }
+                };
+                Ok(())
+            }
             ty::TyInfer(ty::TyVar(_)) => {
                 debug!("assemble_unboxed_closure_candidates: ambiguous self-type");
                 candidates.ambiguous = true;
                 return Ok(());
             }
             _ => { return Ok(()); }
-        };
-
-        debug!("assemble_unboxed_candidates: self_ty={:?} kind={:?} obligation={:?}",
-               self_ty,
-               kind,
-               obligation);
-
-        match self.infcx.closure_kind(closure_def_id) {
-            Some(closure_kind) => {
-                debug!("assemble_unboxed_candidates: closure_kind = {:?}", closure_kind);
-                if closure_kind.extends(kind) {
-                    candidates.vec.push(ClosureCandidate(closure_def_id, substs, kind));
-                }
-            }
-            None => {
-                debug!("assemble_unboxed_candidates: closure_kind not yet known");
-                candidates.vec.push(ClosureCandidate(closure_def_id, substs, kind));
-            }
         }
-
-        Ok(())
     }
 
     /// Implement one of the `Fn()` family for a fn pointer.
@@ -1853,7 +1839,8 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
                          when there are other valid candidates");
                 }
                 ImplCandidate(..) |
-                ClosureCandidate(..) |
+                ClosureCandidate |
+                GeneratorCandidate |
                 FnPointerCandidate |
                 BuiltinObjectCandidate |
                 BuiltinUnsizeCandidate |
@@ -1877,7 +1864,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
                 if other.evaluation == EvaluatedToOk {
                     if let ImplCandidate(victim_def) = victim.candidate {
                         let tcx = self.tcx().global_tcx();
-                        return traits::specializes(tcx, other_def, victim_def) ||
+                        return tcx.specializes((other_def, victim_def)) ||
                             tcx.impls_are_allowed_to_overlap(other_def, victim_def);
                     }
                 }
@@ -1934,7 +1921,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
             ty::TyInfer(ty::IntVar(_)) | ty::TyInfer(ty::FloatVar(_)) |
             ty::TyUint(_) | ty::TyInt(_) | ty::TyBool | ty::TyFloat(_) |
             ty::TyFnDef(..) | ty::TyFnPtr(_) | ty::TyRawPtr(..) |
-            ty::TyChar | ty::TyRef(..) |
+            ty::TyChar | ty::TyRef(..) | ty::TyGenerator(..) |
             ty::TyArray(..) | ty::TyClosure(..) | ty::TyNever |
             ty::TyError => {
                 // safe for everything
@@ -1986,7 +1973,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
             }
 
             ty::TyDynamic(..) | ty::TyStr | ty::TySlice(..) |
-            ty::TyClosure(..) |
+            ty::TyClosure(..) | ty::TyGenerator(..) |
             ty::TyRef(_, ty::TypeAndMut { ty: _, mutbl: hir::MutMutable }) => {
                 Never
             }
@@ -2087,6 +2074,11 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
                 substs.upvar_tys(def_id, self.tcx()).collect()
             }
 
+            ty::TyGenerator(def_id, ref substs, interior) => {
+                let witness = iter::once(interior.witness);
+                substs.upvar_tys(def_id, self.tcx()).chain(witness).collect()
+            }
+
             // for `PhantomData<T>`, we pass `T`
             ty::TyAdt(def, substs) if def.is_phantom_data() => {
                 substs.types().collect()
@@ -2190,12 +2182,16 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
                 Ok(VtableImpl(self.confirm_impl_candidate(obligation, impl_def_id)))
             }
 
-            ClosureCandidate(closure_def_id, substs, kind) => {
-                let vtable_closure =
-                    self.confirm_closure_candidate(obligation, closure_def_id, substs, kind)?;
+            ClosureCandidate => {
+                let vtable_closure = self.confirm_closure_candidate(obligation)?;
                 Ok(VtableClosure(vtable_closure))
             }
 
+            GeneratorCandidate => {
+                let vtable_generator = self.confirm_generator_candidate(obligation)?;
+                Ok(VtableGenerator(vtable_generator))
+            }
+
             BuiltinObjectCandidate => {
                 // This indicates something like `(Trait+Send) :
                 // Send`. In this case, we know that this holds
@@ -2528,23 +2524,84 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
         Ok(VtableFnPointerData { fn_ty: self_ty, nested: obligations })
     }
 
-    fn confirm_closure_candidate(&mut self,
-                                 obligation: &TraitObligation<'tcx>,
-                                 closure_def_id: DefId,
-                                 substs: ty::ClosureSubsts<'tcx>,
-                                 kind: ty::ClosureKind)
-                                 -> Result<VtableClosureData<'tcx, PredicateObligation<'tcx>>,
+    fn confirm_generator_candidate(&mut self,
+                                   obligation: &TraitObligation<'tcx>)
+                                   -> Result<VtableGeneratorData<'tcx, PredicateObligation<'tcx>>,
                                            SelectionError<'tcx>>
     {
-        debug!("confirm_closure_candidate({:?},{:?},{:?})",
+        // ok to skip binder because the substs on generator types never
+        // touch bound regions, they just capture the in-scope
+        // type/region parameters
+        let self_ty = self.infcx.shallow_resolve(obligation.self_ty().skip_binder());
+        let (closure_def_id, substs) = match self_ty.sty {
+            ty::TyGenerator(id, substs, _) => (id, substs),
+            _ => bug!("closure candidate for non-closure {:?}", obligation)
+        };
+
+        debug!("confirm_generator_candidate({:?},{:?},{:?})",
                obligation,
                closure_def_id,
                substs);
 
+        let trait_ref =
+            self.generator_trait_ref_unnormalized(obligation, closure_def_id, substs);
+        let Normalized {
+            value: trait_ref,
+            obligations
+        } = normalize_with_depth(self,
+                                 obligation.param_env,
+                                 obligation.cause.clone(),
+                                 obligation.recursion_depth+1,
+                                 &trait_ref);
+
+        debug!("confirm_generator_candidate(closure_def_id={:?}, trait_ref={:?}, obligations={:?})",
+               closure_def_id,
+               trait_ref,
+               obligations);
+
+        self.confirm_poly_trait_refs(obligation.cause.clone(),
+                                     obligation.param_env,
+                                     obligation.predicate.to_poly_trait_ref(),
+                                     trait_ref)?;
+
+        Ok(VtableGeneratorData {
+            closure_def_id: closure_def_id,
+            substs: substs.clone(),
+            nested: obligations
+        })
+    }
+
+    fn confirm_closure_candidate(&mut self,
+                                 obligation: &TraitObligation<'tcx>)
+                                 -> Result<VtableClosureData<'tcx, PredicateObligation<'tcx>>,
+                                           SelectionError<'tcx>>
+    {
+        debug!("confirm_closure_candidate({:?})", obligation);
+
+        let kind = match self.tcx().lang_items.fn_trait_kind(obligation.predicate.0.def_id()) {
+            Some(k) => k,
+            None => bug!("closure candidate for non-fn trait {:?}", obligation)
+        };
+
+        // ok to skip binder because the substs on closure types never
+        // touch bound regions, they just capture the in-scope
+        // type/region parameters
+        let self_ty = self.infcx.shallow_resolve(obligation.self_ty().skip_binder());
+        let (closure_def_id, substs) = match self_ty.sty {
+            ty::TyClosure(id, substs) => (id, substs),
+            _ => bug!("closure candidate for non-closure {:?}", obligation)
+        };
+
+        let trait_ref =
+            self.closure_trait_ref_unnormalized(obligation, closure_def_id, substs);
         let Normalized {
             value: trait_ref,
             mut obligations
-        } = self.closure_trait_ref(obligation, closure_def_id, substs);
+        } = normalize_with_depth(self,
+                                 obligation.param_env,
+                                 obligation.cause.clone(),
+                                 obligation.recursion_depth+1,
+                                 &trait_ref);
 
         debug!("confirm_closure_candidate(closure_def_id={:?}, trait_ref={:?}, obligations={:?})",
                closure_def_id,
@@ -3011,22 +3068,25 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
         ty::Binder(trait_ref)
     }
 
-    fn closure_trait_ref(&mut self,
-                         obligation: &TraitObligation<'tcx>,
-                         closure_def_id: DefId,
-                         substs: ty::ClosureSubsts<'tcx>)
-                         -> Normalized<'tcx, ty::PolyTraitRef<'tcx>>
+    fn generator_trait_ref_unnormalized(&mut self,
+                                      obligation: &TraitObligation<'tcx>,
+                                      closure_def_id: DefId,
+                                      substs: ty::ClosureSubsts<'tcx>)
+                                      -> ty::PolyTraitRef<'tcx>
     {
-        let trait_ref = self.closure_trait_ref_unnormalized(
-            obligation, closure_def_id, substs);
+        let gen_sig = self.infcx.generator_sig(closure_def_id).unwrap()
+            .subst(self.tcx(), substs.substs);
+        let ty::Binder((trait_ref, ..)) =
+            self.tcx().generator_trait_ref_and_outputs(obligation.predicate.def_id(),
+                                                       obligation.predicate.0.self_ty(), // (1)
+                                                       gen_sig);
+        // (1) Feels icky to skip the binder here, but OTOH we know
+        // that the self-type is an generator type and hence is
+        // in fact unparameterized (or at least does not reference any
+        // regions bound in the obligation). Still probably some
+        // refactoring could make this nicer.
 
-        // A closure signature can contain associated types which
-        // must be normalized.
-        normalize_with_depth(self,
-                             obligation.param_env,
-                             obligation.cause.clone(),
-                             obligation.recursion_depth+1,
-                             &trait_ref)
+        ty::Binder(trait_ref)
     }
 
     /// Returns the obligations that are implied by instantiating an
diff --git a/src/librustc/traits/specialize/mod.rs b/src/librustc/traits/specialize/mod.rs
index 7c916e162a4ff..2dd6ca4b5a928 100644
--- a/src/librustc/traits/specialize/mod.rs
+++ b/src/librustc/traits/specialize/mod.rs
@@ -150,15 +150,12 @@ pub fn find_associated_item<'a, 'tcx>(
 /// Specialization is determined by the sets of types to which the impls apply;
 /// impl1 specializes impl2 if it applies to a subset of the types impl2 applies
 /// to.
-pub fn specializes<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
-                             impl1_def_id: DefId,
-                             impl2_def_id: DefId) -> bool {
+pub(super) fn specializes<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
+                                    (impl1_def_id, impl2_def_id): (DefId, DefId))
+    -> bool
+{
     debug!("specializes({:?}, {:?})", impl1_def_id, impl2_def_id);
 
-    if let Some(r) = tcx.specializes_cache.borrow().check(impl1_def_id, impl2_def_id) {
-        return r;
-    }
-
     // The feature gate should prevent introducing new specializations, but not
     // taking advantage of upstream ones.
     if !tcx.sess.features.borrow().specialization &&
@@ -188,7 +185,7 @@ pub fn specializes<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
     let impl1_trait_ref = tcx.impl_trait_ref(impl1_def_id).unwrap();
 
     // Create a infcx, taking the predicates of impl1 as assumptions:
-    let result = tcx.infer_ctxt().enter(|infcx| {
+    tcx.infer_ctxt().enter(|infcx| {
         // Normalize the trait reference. The WF rules ought to ensure
         // that this always succeeds.
         let impl1_trait_ref =
@@ -204,10 +201,7 @@ pub fn specializes<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 
         // Attempt to prove that impl2 applies, given all of the above.
         fulfill_implication(&infcx, penv, impl1_trait_ref, impl2_def_id).is_ok()
-    });
-
-    tcx.specializes_cache.borrow_mut().insert(impl1_def_id, impl2_def_id, result);
-    result
+    })
 }
 
 /// Attempt to fulfill all obligations of `target_impl` after unification with
diff --git a/src/librustc/traits/specialize/specialization_graph.rs b/src/librustc/traits/specialize/specialization_graph.rs
index 8b31cb599e45d..5242accceabb3 100644
--- a/src/librustc/traits/specialize/specialization_graph.rs
+++ b/src/librustc/traits/specialize/specialization_graph.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use super::{OverlapError, specializes};
+use super::OverlapError;
 
 use hir::def_id::DefId;
 use traits;
@@ -118,8 +118,8 @@ impl<'a, 'gcx, 'tcx> Children {
                         return Ok((false, false));
                     }
 
-                    let le = specializes(tcx, impl_def_id, possible_sibling);
-                    let ge = specializes(tcx, possible_sibling, impl_def_id);
+                    let le = tcx.specializes((impl_def_id, possible_sibling));
+                    let ge = tcx.specializes((possible_sibling, impl_def_id));
 
                     if le == ge {
                         // overlap, but no specialization; error out
diff --git a/src/librustc/traits/structural_impls.rs b/src/librustc/traits/structural_impls.rs
index d913c76ec3c09..674da297cd959 100644
--- a/src/librustc/traits/structural_impls.rs
+++ b/src/librustc/traits/structural_impls.rs
@@ -53,6 +53,9 @@ impl<'tcx, N: fmt::Debug> fmt::Debug for traits::Vtable<'tcx, N> {
             super::VtableClosure(ref d) =>
                 write!(f, "{:?}", d),
 
+            super::VtableGenerator(ref d) =>
+                write!(f, "{:?}", d),
+
             super::VtableFnPointer(ref d) =>
                 write!(f, "VtableFnPointer({:?})", d),
 
@@ -77,6 +80,15 @@ impl<'tcx, N: fmt::Debug> fmt::Debug for traits::VtableImplData<'tcx, N> {
     }
 }
 
+impl<'tcx, N: fmt::Debug> fmt::Debug for traits::VtableGeneratorData<'tcx, N> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "VtableGenerator(closure_def_id={:?}, substs={:?}, nested={:?})",
+               self.closure_def_id,
+               self.substs,
+               self.nested)
+    }
+}
+
 impl<'tcx, N: fmt::Debug> fmt::Debug for traits::VtableClosureData<'tcx, N> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f, "VtableClosure(closure_def_id={:?}, substs={:?}, nested={:?})",
@@ -278,6 +290,19 @@ impl<'a, 'tcx> Lift<'tcx> for traits::Vtable<'a, ()> {
                 })
             }
             traits::VtableDefaultImpl(t) => Some(traits::VtableDefaultImpl(t)),
+            traits::VtableGenerator(traits::VtableGeneratorData {
+                closure_def_id,
+                substs,
+                nested
+            }) => {
+                tcx.lift(&substs).map(|substs| {
+                    traits::VtableGenerator(traits::VtableGeneratorData {
+                        closure_def_id: closure_def_id,
+                        substs: substs,
+                        nested: nested
+                    })
+                })
+            }
             traits::VtableClosure(traits::VtableClosureData {
                 closure_def_id,
                 substs,
@@ -351,6 +376,20 @@ impl<'tcx, N: TypeFoldable<'tcx>> TypeFoldable<'tcx> for traits::VtableImplData<
     }
 }
 
+impl<'tcx, N: TypeFoldable<'tcx>> TypeFoldable<'tcx> for traits::VtableGeneratorData<'tcx, N> {
+    fn super_fold_with<'gcx: 'tcx, F: TypeFolder<'gcx, 'tcx>>(&self, folder: &mut F) -> Self {
+        traits::VtableGeneratorData {
+            closure_def_id: self.closure_def_id,
+            substs: self.substs.fold_with(folder),
+            nested: self.nested.fold_with(folder),
+        }
+    }
+
+    fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        self.substs.visit_with(visitor) || self.nested.visit_with(visitor)
+    }
+}
+
 impl<'tcx, N: TypeFoldable<'tcx>> TypeFoldable<'tcx> for traits::VtableClosureData<'tcx, N> {
     fn super_fold_with<'gcx: 'tcx, F: TypeFolder<'gcx, 'tcx>>(&self, folder: &mut F) -> Self {
         traits::VtableClosureData {
@@ -422,6 +461,9 @@ impl<'tcx, N: TypeFoldable<'tcx>> TypeFoldable<'tcx> for traits::Vtable<'tcx, N>
         match *self {
             traits::VtableImpl(ref v) => traits::VtableImpl(v.fold_with(folder)),
             traits::VtableDefaultImpl(ref t) => traits::VtableDefaultImpl(t.fold_with(folder)),
+            traits::VtableGenerator(ref d) => {
+                traits::VtableGenerator(d.fold_with(folder))
+            }
             traits::VtableClosure(ref d) => {
                 traits::VtableClosure(d.fold_with(folder))
             }
@@ -438,6 +480,7 @@ impl<'tcx, N: TypeFoldable<'tcx>> TypeFoldable<'tcx> for traits::Vtable<'tcx, N>
         match *self {
             traits::VtableImpl(ref v) => v.visit_with(visitor),
             traits::VtableDefaultImpl(ref t) => t.visit_with(visitor),
+            traits::VtableGenerator(ref d) => d.visit_with(visitor),
             traits::VtableClosure(ref d) => d.visit_with(visitor),
             traits::VtableFnPointer(ref d) => d.visit_with(visitor),
             traits::VtableParam(ref n) => n.visit_with(visitor),
diff --git a/src/librustc/traits/util.rs b/src/librustc/traits/util.rs
index dae0c896909c8..28abd1577dade 100644
--- a/src/librustc/traits/util.rs
+++ b/src/librustc/traits/util.rs
@@ -513,6 +513,19 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
         ty::Binder((trait_ref, sig.skip_binder().output()))
     }
 
+    pub fn generator_trait_ref_and_outputs(self,
+        fn_trait_def_id: DefId,
+        self_ty: Ty<'tcx>,
+        sig: ty::PolyGenSig<'tcx>)
+        -> ty::Binder<(ty::TraitRef<'tcx>, Ty<'tcx>, Ty<'tcx>)>
+    {
+        let trait_ref = ty::TraitRef {
+            def_id: fn_trait_def_id,
+            substs: self.mk_substs_trait(self_ty, &[]),
+        };
+        ty::Binder((trait_ref, sig.skip_binder().yield_ty, sig.skip_binder().return_ty))
+    }
+
     pub fn impl_is_default(self, node_item_def_id: DefId) -> bool {
         match self.hir.as_local_node_id(node_item_def_id) {
             Some(node_id) => {
diff --git a/src/librustc/ty/context.rs b/src/librustc/ty/context.rs
index 6ce2232eb3e5d..f475baf19949f 100644
--- a/src/librustc/ty/context.rs
+++ b/src/librustc/ty/context.rs
@@ -14,8 +14,8 @@ use dep_graph::DepGraph;
 use errors::DiagnosticBuilder;
 use session::Session;
 use middle;
-use hir::{TraitMap};
-use hir::def::{Def, ExportMap};
+use hir::{TraitCandidate, HirId};
+use hir::def::{Def, Export};
 use hir::def_id::{CrateNum, DefId, LOCAL_CRATE};
 use hir::map as hir_map;
 use hir::map::DefPathHash;
@@ -32,7 +32,7 @@ use ty::ReprOptions;
 use traits;
 use ty::{self, Ty, TypeAndMut};
 use ty::{TyS, TypeVariants, Slice};
-use ty::{AdtKind, AdtDef, ClosureSubsts, Region};
+use ty::{AdtKind, AdtDef, ClosureSubsts, GeneratorInterior, Region};
 use hir::FreevarMap;
 use ty::{PolyFnSig, InferTy, ParamTy, ProjectionTy, ExistentialPredicate, Predicate};
 use ty::RegionKind;
@@ -340,6 +340,10 @@ pub struct TypeckTables<'tcx> {
     /// that caused the closure to be this kind.
     closure_kinds: ItemLocalMap<(ty::ClosureKind, Option<(Span, ast::Name)>)>,
 
+    generator_sigs: ItemLocalMap<Option<ty::GenSig<'tcx>>>,
+
+    generator_interiors: ItemLocalMap<ty::GeneratorInterior<'tcx>>,
+
     /// For each fn, records the "liberated" types of its arguments
     /// and return type. Liberated means that all bound regions
     /// (including late-bound regions) are replaced with free
@@ -381,6 +385,8 @@ impl<'tcx> TypeckTables<'tcx> {
             adjustments: ItemLocalMap(),
             pat_binding_modes: ItemLocalMap(),
             upvar_capture_map: FxHashMap(),
+            generator_sigs: ItemLocalMap(),
+            generator_interiors: ItemLocalMap(),
             closure_tys: ItemLocalMap(),
             closure_kinds: ItemLocalMap(),
             liberated_fn_sigs: ItemLocalMap(),
@@ -634,6 +640,42 @@ impl<'tcx> TypeckTables<'tcx> {
             data: &mut self.cast_kinds
         }
     }
+
+    pub fn generator_sigs(&self)
+        -> LocalTableInContext<Option<ty::GenSig<'tcx>>>
+    {
+        LocalTableInContext {
+            local_id_root: self.local_id_root,
+            data: &self.generator_sigs,
+        }
+    }
+
+    pub fn generator_sigs_mut(&mut self)
+        -> LocalTableInContextMut<Option<ty::GenSig<'tcx>>>
+    {
+        LocalTableInContextMut {
+            local_id_root: self.local_id_root,
+            data: &mut self.generator_sigs,
+        }
+    }
+
+    pub fn generator_interiors(&self)
+        -> LocalTableInContext<ty::GeneratorInterior<'tcx>>
+    {
+        LocalTableInContext {
+            local_id_root: self.local_id_root,
+            data: &self.generator_interiors,
+        }
+    }
+
+    pub fn generator_interiors_mut(&mut self)
+        -> LocalTableInContextMut<ty::GeneratorInterior<'tcx>>
+    {
+        LocalTableInContextMut {
+            local_id_root: self.local_id_root,
+            data: &mut self.generator_interiors,
+        }
+    }
 }
 
 impl<'a, 'gcx, 'tcx> HashStable<StableHashingContext<'a, 'gcx, 'tcx>> for TypeckTables<'gcx> {
@@ -658,6 +700,8 @@ impl<'a, 'gcx, 'tcx> HashStable<StableHashingContext<'a, 'gcx, 'tcx>> for Typeck
             ref used_trait_imports,
             tainted_by_errors,
             ref free_region_map,
+            ref generator_sigs,
+            ref generator_interiors,
         } = *self;
 
         hcx.with_node_id_hashing_mode(NodeIdHashingMode::HashDefPath, |hcx| {
@@ -691,6 +735,8 @@ impl<'a, 'gcx, 'tcx> HashStable<StableHashingContext<'a, 'gcx, 'tcx>> for Typeck
             ich::hash_stable_itemlocalmap(hcx, hasher, liberated_fn_sigs);
             ich::hash_stable_itemlocalmap(hcx, hasher, fru_field_types);
             ich::hash_stable_itemlocalmap(hcx, hasher, cast_kinds);
+            ich::hash_stable_itemlocalmap(hcx, hasher, generator_sigs);
+            ich::hash_stable_itemlocalmap(hcx, hasher, generator_interiors);
 
             ich::hash_stable_hashset(hcx, hasher, used_trait_imports, |hcx, def_id| {
                 hcx.def_path_hash(*def_id)
@@ -762,8 +808,6 @@ pub struct GlobalCtxt<'tcx> {
 
     pub sess: &'tcx Session,
 
-    pub specializes_cache: RefCell<traits::SpecializesCache>,
-
     pub trans_trait_caches: traits::trans::TransTraitCaches<'tcx>,
 
     pub dep_graph: DepGraph,
@@ -773,10 +817,10 @@ pub struct GlobalCtxt<'tcx> {
 
     /// Map indicating what traits are in scope for places where this
     /// is relevant; generated by resolve.
-    pub trait_map: TraitMap,
+    trait_map: FxHashMap<HirId, Rc<Vec<TraitCandidate>>>,
 
     /// Export map produced by name resolution.
-    pub export_map: ExportMap,
+    export_map: FxHashMap<HirId, Rc<Vec<Export>>>,
 
     pub named_region_map: resolve_lifetime::NamedRegionMap,
 
@@ -809,10 +853,6 @@ pub struct GlobalCtxt<'tcx> {
 
     pub lang_items: middle::lang_items::LanguageItems,
 
-    /// Set of used unsafe nodes (functions or blocks). Unsafe nodes not
-    /// present in this set can be warned about.
-    pub used_unsafe: RefCell<NodeSet>,
-
     /// Set of nodes which mark locals as mutable which end up getting used at
     /// some point. Local variable definitions not in this set can be warned
     /// about.
@@ -1026,14 +1066,17 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
         tls::enter_global(GlobalCtxt {
             sess: s,
             trans_trait_caches: traits::trans::TransTraitCaches::new(dep_graph.clone()),
-            specializes_cache: RefCell::new(traits::SpecializesCache::new()),
             global_arenas: arenas,
             global_interners: interners,
             dep_graph: dep_graph.clone(),
             types: common_types,
             named_region_map,
-            trait_map: resolutions.trait_map,
-            export_map: resolutions.export_map,
+            trait_map: resolutions.trait_map.into_iter().map(|(k, v)| {
+                (hir.node_to_hir_id(k), Rc::new(v))
+            }).collect(),
+            export_map: resolutions.export_map.into_iter().map(|(k, v)| {
+                (hir.node_to_hir_id(k), Rc::new(v))
+            }).collect(),
             hir,
             def_path_hash_to_def_id,
             maps: maps::Maps::new(providers),
@@ -1045,7 +1088,6 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
             normalized_cache: RefCell::new(FxHashMap()),
             inhabitedness_cache: RefCell::new(FxHashMap()),
             lang_items,
-            used_unsafe: RefCell::new(NodeSet()),
             used_mut_nodes: RefCell::new(NodeSet()),
             stability: RefCell::new(stability),
             selection_cache: traits::SelectionCache::new(),
@@ -1364,7 +1406,7 @@ impl<'a, 'tcx> TyCtxt<'a, 'tcx, 'tcx> {
     pub fn print_debug_stats(self) {
         sty_debug_print!(
             self,
-            TyAdt, TyArray, TySlice, TyRawPtr, TyRef, TyFnDef, TyFnPtr,
+            TyAdt, TyArray, TySlice, TyRawPtr, TyRef, TyFnDef, TyFnPtr, TyGenerator,
             TyDynamic, TyClosure, TyTuple, TyParam, TyInfer, TyProjection, TyAnon);
 
         println!("Substs interner: #{}", self.interners.substs.borrow().len());
@@ -1719,6 +1761,14 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
         self.mk_ty(TyClosure(closure_id, closure_substs))
     }
 
+    pub fn mk_generator(self,
+                        id: DefId,
+                        closure_substs: ClosureSubsts<'tcx>,
+                        interior: GeneratorInterior<'tcx>)
+                        -> Ty<'tcx> {
+        self.mk_ty(TyGenerator(id, closure_substs, interior))
+    }
+
     pub fn mk_var(self, v: TyVid) -> Ty<'tcx> {
         self.mk_infer(TyVar(v))
     }
@@ -1943,3 +1993,20 @@ impl<T, R, E> InternIteratorElement<T, R> for Result<T, E> {
         Ok(f(&iter.collect::<Result<AccumulateVec<[_; 8]>, _>>()?))
     }
 }
+
+fn in_scope_traits<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, id: HirId)
+    -> Option<Rc<Vec<TraitCandidate>>>
+{
+    tcx.gcx.trait_map.get(&id).cloned()
+}
+
+fn module_exports<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, id: HirId)
+    -> Option<Rc<Vec<Export>>>
+{
+    tcx.gcx.export_map.get(&id).cloned()
+}
+
+pub fn provide(providers: &mut ty::maps::Providers) {
+    providers.in_scope_traits = in_scope_traits;
+    providers.module_exports = module_exports;
+}
diff --git a/src/librustc/ty/error.rs b/src/librustc/ty/error.rs
index 86a4f66918965..49d7f40000f07 100644
--- a/src/librustc/ty/error.rs
+++ b/src/librustc/ty/error.rs
@@ -36,11 +36,11 @@ pub enum TypeError<'tcx> {
     TupleSize(ExpectedFound<usize>),
     FixedArraySize(ExpectedFound<usize>),
     ArgCount,
+
     RegionsDoesNotOutlive(Region<'tcx>, Region<'tcx>),
-    RegionsNotSame(Region<'tcx>, Region<'tcx>),
-    RegionsNoOverlap(Region<'tcx>, Region<'tcx>),
     RegionsInsufficientlyPolymorphic(BoundRegion, Region<'tcx>),
     RegionsOverlyPolymorphic(BoundRegion, Region<'tcx>),
+
     Sorts(ExpectedFound<Ty<'tcx>>),
     IntMismatch(ExpectedFound<ty::IntVarValue>),
     FloatMismatch(ExpectedFound<ast::FloatTy>),
@@ -110,12 +110,6 @@ impl<'tcx> fmt::Display for TypeError<'tcx> {
             RegionsDoesNotOutlive(..) => {
                 write!(f, "lifetime mismatch")
             }
-            RegionsNotSame(..) => {
-                write!(f, "lifetimes are not the same")
-            }
-            RegionsNoOverlap(..) => {
-                write!(f, "lifetimes do not intersect")
-            }
             RegionsInsufficientlyPolymorphic(br, _) => {
                 write!(f,
                        "expected bound lifetime parameter{}{}, found concrete lifetime",
@@ -213,6 +207,7 @@ impl<'a, 'gcx, 'lcx, 'tcx> ty::TyS<'tcx> {
                     |p| format!("trait {}", tcx.item_path_str(p.def_id())))
             }
             ty::TyClosure(..) => "closure".to_string(),
+            ty::TyGenerator(..) => "generator".to_string(),
             ty::TyTuple(..) => "tuple".to_string(),
             ty::TyInfer(ty::TyVar(_)) => "inferred type".to_string(),
             ty::TyInfer(ty::IntVar(_)) => "integral variable".to_string(),
@@ -242,33 +237,6 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
         use self::TypeError::*;
 
         match err.clone() {
-            RegionsDoesNotOutlive(subregion, superregion) => {
-                self.note_and_explain_region(db, "", subregion, "...");
-                self.note_and_explain_region(db, "...does not necessarily outlive ",
-                                           superregion, "");
-            }
-            RegionsNotSame(region1, region2) => {
-                self.note_and_explain_region(db, "", region1, "...");
-                self.note_and_explain_region(db, "...is not the same lifetime as ",
-                                           region2, "");
-            }
-            RegionsNoOverlap(region1, region2) => {
-                self.note_and_explain_region(db, "", region1, "...");
-                self.note_and_explain_region(db, "...does not overlap ",
-                                           region2, "");
-            }
-            RegionsInsufficientlyPolymorphic(_, conc_region) => {
-                self.note_and_explain_region(db, "concrete lifetime that was found is ",
-                                           conc_region, "");
-            }
-            RegionsOverlyPolymorphic(_, &ty::ReVar(_)) => {
-                // don't bother to print out the message below for
-                // inference variables, it's not very illuminating.
-            }
-            RegionsOverlyPolymorphic(_, conc_region) => {
-                self.note_and_explain_region(db, "expected concrete lifetime is ",
-                                           conc_region, "");
-            }
             Sorts(values) => {
                 let expected_str = values.expected.sort_string(self);
                 let found_str = values.found.sort_string(self);
diff --git a/src/librustc/ty/fast_reject.rs b/src/librustc/ty/fast_reject.rs
index 68f85ba7d33e2..353a1cd5355b9 100644
--- a/src/librustc/ty/fast_reject.rs
+++ b/src/librustc/ty/fast_reject.rs
@@ -30,6 +30,7 @@ pub enum SimplifiedType {
     TupleSimplifiedType(usize),
     TraitSimplifiedType(DefId),
     ClosureSimplifiedType(DefId),
+    GeneratorSimplifiedType(DefId),
     AnonSimplifiedType(DefId),
     FunctionSimplifiedType(usize),
     ParameterSimplifiedType,
@@ -72,6 +73,9 @@ pub fn simplify_type<'a, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
         ty::TyClosure(def_id, _) => {
             Some(ClosureSimplifiedType(def_id))
         }
+        ty::TyGenerator(def_id, _, _) => {
+            Some(GeneratorSimplifiedType(def_id))
+        }
         ty::TyNever => Some(NeverSimplifiedType),
         ty::TyTuple(ref tys, _) => {
             Some(TupleSimplifiedType(tys.len()))
diff --git a/src/librustc/ty/flags.rs b/src/librustc/ty/flags.rs
index 31ed61a919e7c..27b8d245396c9 100644
--- a/src/librustc/ty/flags.rs
+++ b/src/librustc/ty/flags.rs
@@ -85,6 +85,13 @@ impl FlagComputation {
                 }
             }
 
+            &ty::TyGenerator(_, ref substs, ref interior) => {
+                self.add_flags(TypeFlags::HAS_TY_CLOSURE);
+                self.add_flags(TypeFlags::HAS_LOCAL_NAMES);
+                self.add_substs(&substs.substs);
+                self.add_ty(interior.witness);
+            }
+
             &ty::TyClosure(_, ref substs) => {
                 self.add_flags(TypeFlags::HAS_TY_CLOSURE);
                 self.add_flags(TypeFlags::HAS_LOCAL_NAMES);
diff --git a/src/librustc/ty/item_path.rs b/src/librustc/ty/item_path.rs
index 5caf513981280..eadf80871fc95 100644
--- a/src/librustc/ty/item_path.rs
+++ b/src/librustc/ty/item_path.rs
@@ -345,6 +345,7 @@ pub fn characteristic_def_id_of_type(ty: Ty) -> Option<DefId> {
 
         ty::TyFnDef(def_id, _) |
         ty::TyClosure(def_id, _) => Some(def_id),
+        ty::TyGenerator(def_id, _, _) => Some(def_id),
 
         ty::TyBool |
         ty::TyChar |
diff --git a/src/librustc/ty/layout.rs b/src/librustc/ty/layout.rs
index 4ee9b2e65a782..cf21a66d51538 100644
--- a/src/librustc/ty/layout.rs
+++ b/src/librustc/ty/layout.rs
@@ -1226,7 +1226,17 @@ impl<'a, 'tcx> Layout {
                 Univariant { variant: unit, non_zero: false }
             }
 
-            // Tuples and closures.
+            // Tuples, generators and closures.
+            ty::TyGenerator(def_id, ref substs, _) => {
+                let tys = substs.field_tys(def_id, tcx);
+                let st = Struct::new(dl,
+                    &tys.map(|ty| ty.layout(tcx, param_env))
+                      .collect::<Result<Vec<_>, _>>()?,
+                    &ReprOptions::default(),
+                    StructKind::AlwaysSizedUnivariant, ty)?;
+                Univariant { variant: st, non_zero: false }
+            }
+
             ty::TyClosure(def_id, ref substs) => {
                 let tys = substs.upvar_tys(def_id, tcx);
                 let st = Struct::new(dl,
@@ -2240,11 +2250,15 @@ impl<'a, 'tcx> TyLayout<'tcx> {
             ty::TySlice(element) => element,
             ty::TyStr => tcx.types.u8,
 
-            // Tuples and closures.
+            // Tuples, generators and closures.
             ty::TyClosure(def_id, ref substs) => {
                 substs.upvar_tys(def_id, tcx).nth(i).unwrap()
             }
 
+            ty::TyGenerator(def_id, ref substs, _) => {
+                substs.field_tys(def_id, tcx).nth(i).unwrap()
+            }
+
             ty::TyTuple(tys, _) => tys[i],
 
             // SIMD vector types.
diff --git a/src/librustc/ty/maps.rs b/src/librustc/ty/maps.rs
index a73202ced61e6..5a372dbf89fbf 100644
--- a/src/librustc/ty/maps.rs
+++ b/src/librustc/ty/maps.rs
@@ -11,13 +11,13 @@
 use dep_graph::{DepConstructor, DepNode, DepNodeIndex};
 use errors::{Diagnostic, DiagnosticBuilder};
 use hir::def_id::{CrateNum, DefId, LOCAL_CRATE};
-use hir::def::Def;
-use hir;
+use hir::def::{Def, Export};
+use hir::{self, TraitCandidate, HirId};
 use lint;
 use middle::const_val;
 use middle::cstore::{ExternCrate, LinkagePreference};
 use middle::privacy::AccessLevels;
-use middle::region::RegionMaps;
+use middle::region;
 use mir;
 use mir::transform::{MirSuite, MirPassIndex};
 use session::CompileResult;
@@ -31,6 +31,7 @@ use ty::fast_reject::SimplifiedType;
 use util::nodemap::{DefIdSet, NodeSet};
 use util::common::{profq_msg, ProfileQueriesMsg};
 
+use rustc_data_structures::indexed_set::IdxSetBuf;
 use rustc_data_structures::indexed_vec::IndexVec;
 use rustc_data_structures::fx::FxHashMap;
 use std::cell::{RefCell, RefMut, Cell};
@@ -80,6 +81,15 @@ impl Key for CrateNum {
     }
 }
 
+impl Key for HirId {
+    fn map_crate(&self) -> CrateNum {
+        LOCAL_CRATE
+    }
+    fn default_span(&self, _tcx: TyCtxt) -> Span {
+        DUMMY_SP
+    }
+}
+
 impl Key for DefId {
     fn map_crate(&self) -> CrateNum {
         self.krate
@@ -540,6 +550,24 @@ impl<'tcx> QueryDescription for queries::lint_levels<'tcx> {
     }
 }
 
+impl<'tcx> QueryDescription for queries::specializes<'tcx> {
+    fn describe(_tcx: TyCtxt, _: (DefId, DefId)) -> String {
+        format!("computing whether impls specialize one another")
+    }
+}
+
+impl<'tcx> QueryDescription for queries::in_scope_traits<'tcx> {
+    fn describe(_tcx: TyCtxt, _: HirId) -> String {
+        format!("fetching the traits in scope at a particular ast node")
+    }
+}
+
+impl<'tcx> QueryDescription for queries::module_exports<'tcx> {
+    fn describe(_tcx: TyCtxt, _: HirId) -> String {
+        format!("fetching the exported items for a module")
+    }
+}
+
 // If enabled, send a message to the profile-queries thread
 macro_rules! profq_msg {
     ($tcx:expr, $msg:expr) => {
@@ -566,7 +594,7 @@ macro_rules! profq_key {
 macro_rules! define_maps {
     (<$tcx:tt>
      $($(#[$attr:meta])*
-       [$($modifiers:tt)*] $name:ident: $node:ident($K:ty) -> $V:ty,)*) => {
+       [$($modifiers:tt)*] fn $name:ident: $node:ident($K:ty) -> $V:ty,)*) => {
         define_map_struct! {
             tcx: $tcx,
             input: ($(([$($modifiers)*] [$($attr)*] [$name]))*)
@@ -597,8 +625,15 @@ macro_rules! define_maps {
 
         impl<$tcx> Query<$tcx> {
             pub fn describe(&self, tcx: TyCtxt) -> String {
-                match *self {
-                    $(Query::$name(key) => queries::$name::describe(tcx, key)),*
+                let (r, name) = match *self {
+                    $(Query::$name(key) => {
+                        (queries::$name::describe(tcx, key), stringify!($name))
+                    })*
+                };
+                if tcx.sess.verbose() {
+                    format!("{} [{}]", r, name)
+                } else {
+                    r
                 }
             }
         }
@@ -920,12 +955,12 @@ macro_rules! define_provider_struct {
 // the driver creates (using several `rustc_*` crates).
 define_maps! { <'tcx>
     /// Records the type of every item.
-    [] type_of: TypeOfItem(DefId) -> Ty<'tcx>,
+    [] fn type_of: TypeOfItem(DefId) -> Ty<'tcx>,
 
     /// Maps from the def-id of an item (trait/struct/enum/fn) to its
     /// associated generics and predicates.
-    [] generics_of: GenericsOfItem(DefId) -> &'tcx ty::Generics,
-    [] predicates_of: PredicatesOfItem(DefId) -> ty::GenericPredicates<'tcx>,
+    [] fn generics_of: GenericsOfItem(DefId) -> &'tcx ty::Generics,
+    [] fn predicates_of: PredicatesOfItem(DefId) -> ty::GenericPredicates<'tcx>,
 
     /// Maps from the def-id of a trait to the list of
     /// super-predicates. This is a subset of the full list of
@@ -933,141 +968,145 @@ define_maps! { <'tcx>
     /// evaluate them even during type conversion, often before the
     /// full predicates are available (note that supertraits have
     /// additional acyclicity requirements).
-    [] super_predicates_of: SuperPredicatesOfItem(DefId) -> ty::GenericPredicates<'tcx>,
+    [] fn super_predicates_of: SuperPredicatesOfItem(DefId) -> ty::GenericPredicates<'tcx>,
 
     /// To avoid cycles within the predicates of a single item we compute
     /// per-type-parameter predicates for resolving `T::AssocTy`.
-    [] type_param_predicates: type_param_predicates((DefId, DefId))
+    [] fn type_param_predicates: type_param_predicates((DefId, DefId))
         -> ty::GenericPredicates<'tcx>,
 
-    [] trait_def: TraitDefOfItem(DefId) -> &'tcx ty::TraitDef,
-    [] adt_def: AdtDefOfItem(DefId) -> &'tcx ty::AdtDef,
-    [] adt_destructor: AdtDestructor(DefId) -> Option<ty::Destructor>,
-    [] adt_sized_constraint: SizedConstraint(DefId) -> &'tcx [Ty<'tcx>],
-    [] adt_dtorck_constraint: DtorckConstraint(DefId) -> ty::DtorckConstraint<'tcx>,
+    [] fn trait_def: TraitDefOfItem(DefId) -> &'tcx ty::TraitDef,
+    [] fn adt_def: AdtDefOfItem(DefId) -> &'tcx ty::AdtDef,
+    [] fn adt_destructor: AdtDestructor(DefId) -> Option<ty::Destructor>,
+    [] fn adt_sized_constraint: SizedConstraint(DefId) -> &'tcx [Ty<'tcx>],
+    [] fn adt_dtorck_constraint: DtorckConstraint(DefId) -> ty::DtorckConstraint<'tcx>,
 
     /// True if this is a const fn
-    [] is_const_fn: IsConstFn(DefId) -> bool,
+    [] fn is_const_fn: IsConstFn(DefId) -> bool,
 
     /// True if this is a foreign item (i.e., linked via `extern { ... }`).
-    [] is_foreign_item: IsForeignItem(DefId) -> bool,
+    [] fn is_foreign_item: IsForeignItem(DefId) -> bool,
 
     /// True if this is a default impl (aka impl Foo for ..)
-    [] is_default_impl: IsDefaultImpl(DefId) -> bool,
+    [] fn is_default_impl: IsDefaultImpl(DefId) -> bool,
 
     /// Get a map with the variance of every item; use `item_variance`
     /// instead.
-    [] crate_variances: crate_variances(CrateNum) -> Rc<ty::CrateVariancesMap>,
+    [] fn crate_variances: crate_variances(CrateNum) -> Rc<ty::CrateVariancesMap>,
 
     /// Maps from def-id of a type or region parameter to its
     /// (inferred) variance.
-    [] variances_of: ItemVariances(DefId) -> Rc<Vec<ty::Variance>>,
+    [] fn variances_of: ItemVariances(DefId) -> Rc<Vec<ty::Variance>>,
 
     /// Maps from an impl/trait def-id to a list of the def-ids of its items
-    [] associated_item_def_ids: AssociatedItemDefIds(DefId) -> Rc<Vec<DefId>>,
+    [] fn associated_item_def_ids: AssociatedItemDefIds(DefId) -> Rc<Vec<DefId>>,
 
     /// Maps from a trait item to the trait item "descriptor"
-    [] associated_item: AssociatedItems(DefId) -> ty::AssociatedItem,
+    [] fn associated_item: AssociatedItems(DefId) -> ty::AssociatedItem,
 
-    [] impl_trait_ref: ImplTraitRef(DefId) -> Option<ty::TraitRef<'tcx>>,
-    [] impl_polarity: ImplPolarity(DefId) -> hir::ImplPolarity,
+    [] fn impl_trait_ref: ImplTraitRef(DefId) -> Option<ty::TraitRef<'tcx>>,
+    [] fn impl_polarity: ImplPolarity(DefId) -> hir::ImplPolarity,
 
     /// Maps a DefId of a type to a list of its inherent impls.
     /// Contains implementations of methods that are inherent to a type.
     /// Methods in these implementations don't need to be exported.
-    [] inherent_impls: InherentImpls(DefId) -> Rc<Vec<DefId>>,
+    [] fn inherent_impls: InherentImpls(DefId) -> Rc<Vec<DefId>>,
 
     /// Set of all the def-ids in this crate that have MIR associated with
     /// them. This includes all the body owners, but also things like struct
     /// constructors.
-    [] mir_keys: mir_keys(CrateNum) -> Rc<DefIdSet>,
+    [] fn mir_keys: mir_keys(CrateNum) -> Rc<DefIdSet>,
 
     /// Maps DefId's that have an associated Mir to the result
     /// of the MIR qualify_consts pass. The actual meaning of
     /// the value isn't known except to the pass itself.
-    [] mir_const_qualif: MirConstQualif(DefId) -> u8,
+    [] fn mir_const_qualif: MirConstQualif(DefId) -> (u8, Rc<IdxSetBuf<mir::Local>>),
 
     /// Fetch the MIR for a given def-id up till the point where it is
     /// ready for const evaluation.
     ///
     /// See the README for the `mir` module for details.
-    [] mir_const: MirConst(DefId) -> &'tcx Steal<mir::Mir<'tcx>>,
+    [] fn mir_const: MirConst(DefId) -> &'tcx Steal<mir::Mir<'tcx>>,
 
-    [] mir_validated: MirValidated(DefId) -> &'tcx Steal<mir::Mir<'tcx>>,
+    [] fn mir_validated: MirValidated(DefId) -> &'tcx Steal<mir::Mir<'tcx>>,
 
     /// MIR after our optimization passes have run. This is MIR that is ready
     /// for trans. This is also the only query that can fetch non-local MIR, at present.
-    [] optimized_mir: MirOptimized(DefId) -> &'tcx mir::Mir<'tcx>,
+    [] fn optimized_mir: MirOptimized(DefId) -> &'tcx mir::Mir<'tcx>,
 
     /// Type of each closure. The def ID is the ID of the
     /// expression defining the closure.
-    [] closure_kind: ClosureKind(DefId) -> ty::ClosureKind,
+    [] fn closure_kind: ClosureKind(DefId) -> ty::ClosureKind,
 
     /// The signature of functions and closures.
-    [] fn_sig: FnSignature(DefId) -> ty::PolyFnSig<'tcx>,
+    [] fn fn_sig: FnSignature(DefId) -> ty::PolyFnSig<'tcx>,
+
+    /// Records the signature of each generator. The def ID is the ID of the
+    /// expression defining the closure.
+    [] fn generator_sig: GenSignature(DefId) -> Option<ty::PolyGenSig<'tcx>>,
 
     /// Caches CoerceUnsized kinds for impls on custom types.
-    [] coerce_unsized_info: CoerceUnsizedInfo(DefId)
+    [] fn coerce_unsized_info: CoerceUnsizedInfo(DefId)
         -> ty::adjustment::CoerceUnsizedInfo,
 
-    [] typeck_item_bodies: typeck_item_bodies_dep_node(CrateNum) -> CompileResult,
+    [] fn typeck_item_bodies: typeck_item_bodies_dep_node(CrateNum) -> CompileResult,
 
-    [] typeck_tables_of: TypeckTables(DefId) -> &'tcx ty::TypeckTables<'tcx>,
+    [] fn typeck_tables_of: TypeckTables(DefId) -> &'tcx ty::TypeckTables<'tcx>,
 
-    [] has_typeck_tables: HasTypeckTables(DefId) -> bool,
+    [] fn has_typeck_tables: HasTypeckTables(DefId) -> bool,
 
-    [] coherent_trait: coherent_trait_dep_node((CrateNum, DefId)) -> (),
+    [] fn coherent_trait: coherent_trait_dep_node((CrateNum, DefId)) -> (),
 
-    [] borrowck: BorrowCheck(DefId) -> (),
+    [] fn borrowck: BorrowCheck(DefId) -> (),
     // FIXME: shouldn't this return a `Result<(), BorrowckErrors>` instead?
-    [] mir_borrowck: MirBorrowCheck(DefId) -> (),
+    [] fn mir_borrowck: MirBorrowCheck(DefId) -> (),
 
     /// Gets a complete map from all types to their inherent impls.
     /// Not meant to be used directly outside of coherence.
     /// (Defined only for LOCAL_CRATE)
-    [] crate_inherent_impls: crate_inherent_impls_dep_node(CrateNum) -> CrateInherentImpls,
+    [] fn crate_inherent_impls: crate_inherent_impls_dep_node(CrateNum) -> CrateInherentImpls,
 
     /// Checks all types in the krate for overlap in their inherent impls. Reports errors.
     /// Not meant to be used directly outside of coherence.
     /// (Defined only for LOCAL_CRATE)
-    [] crate_inherent_impls_overlap_check: inherent_impls_overlap_check_dep_node(CrateNum) -> (),
+    [] fn crate_inherent_impls_overlap_check: inherent_impls_overlap_check_dep_node(CrateNum) -> (),
 
     /// Results of evaluating const items or constants embedded in
     /// other items (such as enum variant explicit discriminants).
-    [] const_eval: const_eval_dep_node(ty::ParamEnvAnd<'tcx, (DefId, &'tcx Substs<'tcx>)>)
+    [] fn const_eval: const_eval_dep_node(ty::ParamEnvAnd<'tcx, (DefId, &'tcx Substs<'tcx>)>)
         -> const_val::EvalResult<'tcx>,
 
     /// Performs the privacy check and computes "access levels".
-    [] privacy_access_levels: PrivacyAccessLevels(CrateNum) -> Rc<AccessLevels>,
+    [] fn privacy_access_levels: PrivacyAccessLevels(CrateNum) -> Rc<AccessLevels>,
 
-    [] reachable_set: reachability_dep_node(CrateNum) -> Rc<NodeSet>,
+    [] fn reachable_set: reachability_dep_node(CrateNum) -> Rc<NodeSet>,
 
-    /// Per-function `RegionMaps`. The `DefId` should be the owner-def-id for the fn body;
-    /// in the case of closures or "inline" expressions, this will be redirected to the enclosing
-    /// fn item.
-    [] region_maps: RegionMaps(DefId) -> Rc<RegionMaps>,
+    /// Per-body `region::ScopeTree`. The `DefId` should be the owner-def-id for the body;
+    /// in the case of closures, this will be redirected to the enclosing function.
+    [] fn region_scope_tree: RegionScopeTree(DefId) -> Rc<region::ScopeTree>,
 
-    [] mir_shims: mir_shim_dep_node(ty::InstanceDef<'tcx>) -> &'tcx mir::Mir<'tcx>,
+    [] fn mir_shims: mir_shim_dep_node(ty::InstanceDef<'tcx>) -> &'tcx mir::Mir<'tcx>,
 
-    [] def_symbol_name: SymbolName(DefId) -> ty::SymbolName,
-    [] symbol_name: symbol_name_dep_node(ty::Instance<'tcx>) -> ty::SymbolName,
+    [] fn def_symbol_name: SymbolName(DefId) -> ty::SymbolName,
+    [] fn symbol_name: symbol_name_dep_node(ty::Instance<'tcx>) -> ty::SymbolName,
 
-    [] describe_def: DescribeDef(DefId) -> Option<Def>,
-    [] def_span: DefSpan(DefId) -> Span,
-    [] stability: Stability(DefId) -> Option<attr::Stability>,
-    [] deprecation: Deprecation(DefId) -> Option<attr::Deprecation>,
-    [] item_attrs: ItemAttrs(DefId) -> Rc<[ast::Attribute]>,
-    [] fn_arg_names: FnArgNames(DefId) -> Vec<ast::Name>,
-    [] impl_parent: ImplParent(DefId) -> Option<DefId>,
-    [] trait_of_item: TraitOfItem(DefId) -> Option<DefId>,
-    [] is_exported_symbol: IsExportedSymbol(DefId) -> bool,
-    [] item_body_nested_bodies: ItemBodyNestedBodies(DefId) -> Rc<BTreeMap<hir::BodyId, hir::Body>>,
-    [] const_is_rvalue_promotable_to_static: ConstIsRvaluePromotableToStatic(DefId) -> bool,
-    [] is_mir_available: IsMirAvailable(DefId) -> bool,
+    [] fn describe_def: DescribeDef(DefId) -> Option<Def>,
+    [] fn def_span: DefSpan(DefId) -> Span,
+    [] fn stability: Stability(DefId) -> Option<attr::Stability>,
+    [] fn deprecation: Deprecation(DefId) -> Option<attr::Deprecation>,
+    [] fn item_attrs: ItemAttrs(DefId) -> Rc<[ast::Attribute]>,
+    [] fn fn_arg_names: FnArgNames(DefId) -> Vec<ast::Name>,
+    [] fn impl_parent: ImplParent(DefId) -> Option<DefId>,
+    [] fn trait_of_item: TraitOfItem(DefId) -> Option<DefId>,
+    [] fn is_exported_symbol: IsExportedSymbol(DefId) -> bool,
+    [] fn item_body_nested_bodies: ItemBodyNestedBodies(DefId)
+        -> Rc<BTreeMap<hir::BodyId, hir::Body>>,
+    [] fn const_is_rvalue_promotable_to_static: ConstIsRvaluePromotableToStatic(DefId) -> bool,
+    [] fn is_mir_available: IsMirAvailable(DefId) -> bool,
 
-    [] trait_impls_of: TraitImpls(DefId) -> Rc<ty::trait_def::TraitImpls>,
-    [] specialization_graph_of: SpecializationGraph(DefId) -> Rc<specialization_graph::Graph>,
-    [] is_object_safe: ObjectSafety(DefId) -> bool,
+    [] fn trait_impls_of: TraitImpls(DefId) -> Rc<ty::trait_def::TraitImpls>,
+    [] fn specialization_graph_of: SpecializationGraph(DefId) -> Rc<specialization_graph::Graph>,
+    [] fn is_object_safe: ObjectSafety(DefId) -> bool,
 
     // Get the ParameterEnvironment for a given item; this environment
     // will be in "user-facing" mode, meaning that it is suitabe for
@@ -1075,28 +1114,32 @@ define_maps! { <'tcx>
     // associated types. This is almost always what you want,
     // unless you are doing MIR optimizations, in which case you
     // might want to use `reveal_all()` method to change modes.
-    [] param_env: ParamEnv(DefId) -> ty::ParamEnv<'tcx>,
+    [] fn param_env: ParamEnv(DefId) -> ty::ParamEnv<'tcx>,
 
     // Trait selection queries. These are best used by invoking `ty.moves_by_default()`,
     // `ty.is_copy()`, etc, since that will prune the environment where possible.
-    [] is_copy_raw: is_copy_dep_node(ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> bool,
-    [] is_sized_raw: is_sized_dep_node(ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> bool,
-    [] is_freeze_raw: is_freeze_dep_node(ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> bool,
-    [] needs_drop_raw: needs_drop_dep_node(ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> bool,
-    [] layout_raw: layout_dep_node(ty::ParamEnvAnd<'tcx, Ty<'tcx>>)
+    [] fn is_copy_raw: is_copy_dep_node(ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> bool,
+    [] fn is_sized_raw: is_sized_dep_node(ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> bool,
+    [] fn is_freeze_raw: is_freeze_dep_node(ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> bool,
+    [] fn needs_drop_raw: needs_drop_dep_node(ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> bool,
+    [] fn layout_raw: layout_dep_node(ty::ParamEnvAnd<'tcx, Ty<'tcx>>)
                                   -> Result<&'tcx Layout, LayoutError<'tcx>>,
 
-    [] dylib_dependency_formats: DylibDepFormats(DefId)
+    [] fn dylib_dependency_formats: DylibDepFormats(DefId)
                                     -> Rc<Vec<(CrateNum, LinkagePreference)>>,
 
-    [] is_allocator: IsAllocator(DefId) -> bool,
-    [] is_panic_runtime: IsPanicRuntime(DefId) -> bool,
-    [] is_compiler_builtins: IsCompilerBuiltins(DefId) -> bool,
-    [] has_global_allocator: HasGlobalAllocator(DefId) -> bool,
+    [] fn is_allocator: IsAllocator(DefId) -> bool,
+    [] fn is_panic_runtime: IsPanicRuntime(DefId) -> bool,
+    [] fn is_compiler_builtins: IsCompilerBuiltins(DefId) -> bool,
+    [] fn has_global_allocator: HasGlobalAllocator(DefId) -> bool,
+
+    [] fn extern_crate: ExternCrate(DefId) -> Rc<Option<ExternCrate>>,
 
-    [] extern_crate: ExternCrate(DefId) -> Rc<Option<ExternCrate>>,
+    [] fn lint_levels: lint_levels(CrateNum) -> Rc<lint::LintLevelMap>,
 
-    [] lint_levels: lint_levels(CrateNum) -> Rc<lint::LintLevelMap>,
+    [] fn specializes: specializes_node((DefId, DefId)) -> bool,
+    [] fn in_scope_traits: InScopeTraits(HirId) -> Option<Rc<Vec<TraitCandidate>>>,
+    [] fn module_exports: ModuleExports(HirId) -> Option<Rc<Vec<Export>>>,
 }
 
 fn type_param_predicates<'tcx>((item_id, param_id): (DefId, DefId)) -> DepConstructor<'tcx> {
@@ -1172,3 +1215,7 @@ fn layout_dep_node<'tcx>(_: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> DepConstructor<'
 fn lint_levels<'tcx>(_: CrateNum) -> DepConstructor<'tcx> {
     DepConstructor::LintLevels
 }
+
+fn specializes_node<'tcx>((a, b): (DefId, DefId)) -> DepConstructor<'tcx> {
+    DepConstructor::Specializes { impl1: a, impl2: b }
+}
diff --git a/src/librustc/ty/mod.rs b/src/librustc/ty/mod.rs
index 6597dccf25816..1851e1b8d34bb 100644
--- a/src/librustc/ty/mod.rs
+++ b/src/librustc/ty/mod.rs
@@ -23,8 +23,8 @@ use middle::const_val::ConstVal;
 use middle::lang_items::{FnTraitLangItem, FnMutTraitLangItem, FnOnceTraitLangItem};
 use middle::privacy::AccessLevels;
 use middle::resolve_lifetime::ObjectLifetimeDefault;
-use middle::region::CodeExtent;
 use mir::Mir;
+use mir::GeneratorLayout;
 use traits;
 use ty;
 use ty::subst::{Subst, Substs};
@@ -59,9 +59,9 @@ use rustc_data_structures::transitive_relation::TransitiveRelation;
 use hir;
 
 pub use self::sty::{Binder, DebruijnIndex};
-pub use self::sty::{FnSig, PolyFnSig};
+pub use self::sty::{FnSig, GenSig, PolyFnSig, PolyGenSig};
 pub use self::sty::{InferTy, ParamTy, ProjectionTy, ExistentialPredicate};
-pub use self::sty::{ClosureSubsts, TypeAndMut};
+pub use self::sty::{ClosureSubsts, GeneratorInterior, TypeAndMut};
 pub use self::sty::{TraitRef, TypeVariants, PolyTraitRef};
 pub use self::sty::{ExistentialTraitRef, PolyExistentialTraitRef};
 pub use self::sty::{ExistentialProjection, PolyExistentialProjection};
@@ -409,6 +409,8 @@ bitflags! {
         const HAS_FREE_REGIONS   = 1 << 6,
         const HAS_TY_ERR         = 1 << 7,
         const HAS_PROJECTION     = 1 << 8,
+
+        // FIXME: Rename this to the actual property since it's used for generators too
         const HAS_TY_CLOSURE     = 1 << 9,
 
         // true if there are "names" of types and regions and so forth
@@ -1706,7 +1708,7 @@ impl<'a, 'gcx, 'tcx> AdtDef {
         let result = match ty.sty {
             TyBool | TyChar | TyInt(..) | TyUint(..) | TyFloat(..) |
             TyRawPtr(..) | TyRef(..) | TyFnDef(..) | TyFnPtr(_) |
-            TyArray(..) | TyClosure(..) | TyNever => {
+            TyArray(..) | TyClosure(..) | TyGenerator(..) | TyNever => {
                 vec![]
             }
 
@@ -2039,6 +2041,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
             hir::ExprBox(..) |
             hir::ExprAddrOf(..) |
             hir::ExprBinary(..) |
+            hir::ExprYield(..) |
             hir::ExprCast(..) => {
                 false
             }
@@ -2271,6 +2274,10 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
         self.trait_def(trait_def_id).has_default_impl
     }
 
+    pub fn generator_layout(self, def_id: DefId) -> &'tcx GeneratorLayout<'tcx> {
+        self.optimized_mir(def_id).generator_layout.as_ref().unwrap()
+    }
+
     /// Given the def_id of an impl, return the def_id of the trait it implements.
     /// If it implements no trait, return `None`.
     pub fn trait_id_of_impl(self, def_id: DefId) -> Option<DefId> {
@@ -2301,10 +2308,6 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
         }
     }
 
-    pub fn node_scope_region(self, id: NodeId) -> Region<'tcx> {
-        self.mk_region(ty::ReScope(CodeExtent::Misc(id)))
-    }
-
     /// Looks up the span of `impl_did` if the impl is local; otherwise returns `Err`
     /// with the name of the crate containing the impl.
     pub fn span_of_impl(self, impl_did: DefId) -> Result<Span, Symbol> {
@@ -2509,6 +2512,7 @@ fn param_env<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 
 pub fn provide(providers: &mut ty::maps::Providers) {
     util::provide(providers);
+    context::provide(providers);
     *providers = ty::maps::Providers {
         associated_item,
         associated_item_def_ids,
diff --git a/src/librustc/ty/outlives.rs b/src/librustc/ty/outlives.rs
index ab1b1b3857d00..657ed4077911c 100644
--- a/src/librustc/ty/outlives.rs
+++ b/src/librustc/ty/outlives.rs
@@ -115,6 +115,16 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
                 }
             }
 
+            ty::TyGenerator(def_id, ref substs, ref interior) => {
+                // Same as the closure case
+                for upvar_ty in substs.upvar_tys(def_id, *self) {
+                    self.compute_components(upvar_ty, out);
+                }
+
+                // But generators can have additional interior types
+                self.compute_components(interior.witness, out);
+            }
+
             // OutlivesTypeParameterEnv -- the actual checking that `X:'a`
             // is implied by the environment is done in regionck.
             ty::TyParam(p) => {
diff --git a/src/librustc/ty/relate.rs b/src/librustc/ty/relate.rs
index c035817d66db0..0ff3199689c19 100644
--- a/src/librustc/ty/relate.rs
+++ b/src/librustc/ty/relate.rs
@@ -389,6 +389,18 @@ pub fn super_relate_tys<'a, 'gcx, 'tcx, R>(relation: &mut R,
             Ok(tcx.mk_dynamic(relation.relate(a_obj, b_obj)?, region_bound))
         }
 
+        (&ty::TyGenerator(a_id, a_substs, a_interior),
+         &ty::TyGenerator(b_id, b_substs, b_interior))
+            if a_id == b_id =>
+        {
+            // All TyGenerator types with the same id represent
+            // the (anonymous) type of the same generator expression. So
+            // all of their regions should be equated.
+            let substs = relation.relate(&a_substs, &b_substs)?;
+            let interior = relation.relate(&a_interior, &b_interior)?;
+            Ok(tcx.mk_generator(a_id, substs, interior))
+        }
+
         (&ty::TyClosure(a_id, a_substs),
          &ty::TyClosure(b_id, b_substs))
             if a_id == b_id =>
@@ -512,6 +524,18 @@ impl<'tcx> Relate<'tcx> for ty::ClosureSubsts<'tcx> {
     }
 }
 
+impl<'tcx> Relate<'tcx> for ty::GeneratorInterior<'tcx> {
+    fn relate<'a, 'gcx, R>(relation: &mut R,
+                           a: &ty::GeneratorInterior<'tcx>,
+                           b: &ty::GeneratorInterior<'tcx>)
+                           -> RelateResult<'tcx, ty::GeneratorInterior<'tcx>>
+        where R: TypeRelation<'a, 'gcx, 'tcx>, 'gcx: 'a+'tcx, 'tcx: 'a
+    {
+        let interior = relation.relate(&a.witness, &b.witness)?;
+        Ok(ty::GeneratorInterior::new(interior))
+    }
+}
+
 impl<'tcx> Relate<'tcx> for &'tcx Substs<'tcx> {
     fn relate<'a, 'gcx, R>(relation: &mut R,
                            a: &&'tcx Substs<'tcx>,
diff --git a/src/librustc/ty/structural_impls.rs b/src/librustc/ty/structural_impls.rs
index e41eb079b3782..44b505e19658f 100644
--- a/src/librustc/ty/structural_impls.rs
+++ b/src/librustc/ty/structural_impls.rs
@@ -29,6 +29,15 @@ impl<'tcx, A: Lift<'tcx>, B: Lift<'tcx>> Lift<'tcx> for (A, B) {
     }
 }
 
+impl<'tcx, A: Lift<'tcx>, B: Lift<'tcx>, C: Lift<'tcx>> Lift<'tcx> for (A, B, C) {
+    type Lifted = (A::Lifted, B::Lifted, C::Lifted);
+    fn lift_to_tcx<'a, 'gcx>(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> Option<Self::Lifted> {
+        tcx.lift(&self.0).and_then(|a| {
+            tcx.lift(&self.1).and_then(|b| tcx.lift(&self.2).map(|c| (a, b, c)))
+        })
+    }
+}
+
 impl<'tcx, T: Lift<'tcx>> Lift<'tcx> for Option<T> {
     type Lifted = Option<T::Lifted>;
     fn lift_to_tcx<'a, 'gcx>(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> Option<Self::Lifted> {
@@ -220,6 +229,15 @@ impl<'a, 'tcx> Lift<'tcx> for ty::ClosureSubsts<'a> {
     }
 }
 
+impl<'a, 'tcx> Lift<'tcx> for ty::GeneratorInterior<'a> {
+    type Lifted = ty::GeneratorInterior<'tcx>;
+    fn lift_to_tcx<'b, 'gcx>(&self, tcx: TyCtxt<'b, 'gcx, 'tcx>) -> Option<Self::Lifted> {
+        tcx.lift(&self.witness).map(|witness| {
+            ty::GeneratorInterior { witness }
+        })
+    }
+}
+
 impl<'a, 'tcx> Lift<'tcx> for ty::adjustment::Adjustment<'a> {
     type Lifted = ty::adjustment::Adjustment<'tcx>;
     fn lift_to_tcx<'b, 'gcx>(&self, tcx: TyCtxt<'b, 'gcx, 'tcx>) -> Option<Self::Lifted> {
@@ -283,6 +301,19 @@ impl<'a, 'tcx> Lift<'tcx> for ty::adjustment::AutoBorrow<'a> {
     }
 }
 
+impl<'a, 'tcx> Lift<'tcx> for ty::GenSig<'a> {
+    type Lifted = ty::GenSig<'tcx>;
+    fn lift_to_tcx<'b, 'gcx>(&self, tcx: TyCtxt<'b, 'gcx, 'tcx>) -> Option<Self::Lifted> {
+        tcx.lift(&(self.yield_ty, self.return_ty))
+            .map(|(yield_ty, return_ty)| {
+                ty::GenSig {
+                    yield_ty,
+                    return_ty,
+                }
+            })
+    }
+}
+
 impl<'a, 'tcx> Lift<'tcx> for ty::FnSig<'a> {
     type Lifted = ty::FnSig<'tcx>;
     fn lift_to_tcx<'b, 'gcx>(&self, tcx: TyCtxt<'b, 'gcx, 'tcx>) -> Option<Self::Lifted> {
@@ -340,12 +371,6 @@ impl<'a, 'tcx> Lift<'tcx> for ty::error::TypeError<'a> {
             RegionsDoesNotOutlive(a, b) => {
                 return tcx.lift(&(a, b)).map(|(a, b)| RegionsDoesNotOutlive(a, b))
             }
-            RegionsNotSame(a, b) => {
-                return tcx.lift(&(a, b)).map(|(a, b)| RegionsNotSame(a, b))
-            }
-            RegionsNoOverlap(a, b) => {
-                return tcx.lift(&(a, b)).map(|(a, b)| RegionsNoOverlap(a, b))
-            }
             RegionsInsufficientlyPolymorphic(a, b) => {
                 return tcx.lift(&b).map(|b| RegionsInsufficientlyPolymorphic(a, b))
             }
@@ -396,7 +421,7 @@ macro_rules! CopyImpls {
     }
 }
 
-CopyImpls! { (), hir::Unsafety, abi::Abi, hir::def_id::DefId }
+CopyImpls! { (), hir::Unsafety, abi::Abi, hir::def_id::DefId, ::mir::Local }
 
 impl<'tcx, T:TypeFoldable<'tcx>, U:TypeFoldable<'tcx>> TypeFoldable<'tcx> for (T, U) {
     fn super_fold_with<'gcx: 'tcx, F: TypeFolder<'gcx, 'tcx>>(&self, folder: &mut F) -> (T, U) {
@@ -539,6 +564,9 @@ impl<'tcx> TypeFoldable<'tcx> for Ty<'tcx> {
             ty::TyRef(ref r, tm) => {
                 ty::TyRef(r.fold_with(folder), tm.fold_with(folder))
             }
+            ty::TyGenerator(did, substs, interior) => {
+                ty::TyGenerator(did, substs.fold_with(folder), interior.fold_with(folder))
+            }
             ty::TyClosure(did, substs) => ty::TyClosure(did, substs.fold_with(folder)),
             ty::TyProjection(ref data) => ty::TyProjection(data.fold_with(folder)),
             ty::TyAnon(did, substs) => ty::TyAnon(did, substs.fold_with(folder)),
@@ -570,6 +598,9 @@ impl<'tcx> TypeFoldable<'tcx> for Ty<'tcx> {
             ty::TyFnDef(_, substs) => substs.visit_with(visitor),
             ty::TyFnPtr(ref f) => f.visit_with(visitor),
             ty::TyRef(r, ref tm) => r.visit_with(visitor) || tm.visit_with(visitor),
+            ty::TyGenerator(_did, ref substs, ref interior) => {
+                substs.visit_with(visitor) || interior.visit_with(visitor)
+            }
             ty::TyClosure(_did, ref substs) => substs.visit_with(visitor),
             ty::TyProjection(ref data) => data.visit_with(visitor),
             ty::TyAnon(_, ref substs) => substs.visit_with(visitor),
@@ -594,6 +625,20 @@ impl<'tcx> TypeFoldable<'tcx> for ty::TypeAndMut<'tcx> {
     }
 }
 
+impl<'tcx> TypeFoldable<'tcx> for ty::GenSig<'tcx> {
+    fn super_fold_with<'gcx: 'tcx, F: TypeFolder<'gcx, 'tcx>>(&self, folder: &mut F) -> Self {
+        ty::GenSig {
+            yield_ty: self.yield_ty.fold_with(folder),
+            return_ty: self.return_ty.fold_with(folder),
+        }
+    }
+
+    fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        self.yield_ty.visit_with(visitor) ||
+        self.return_ty.visit_with(visitor)
+    }
+}
+
 impl<'tcx> TypeFoldable<'tcx> for ty::FnSig<'tcx> {
     fn super_fold_with<'gcx: 'tcx, F: TypeFolder<'gcx, 'tcx>>(&self, folder: &mut F) -> Self {
         let inputs_and_output = self.inputs_and_output.fold_with(folder);
@@ -684,6 +729,16 @@ impl<'tcx> TypeFoldable<'tcx> for ty::ClosureSubsts<'tcx> {
     }
 }
 
+impl<'tcx> TypeFoldable<'tcx> for ty::GeneratorInterior<'tcx> {
+    fn super_fold_with<'gcx: 'tcx, F: TypeFolder<'gcx, 'tcx>>(&self, folder: &mut F) -> Self {
+        ty::GeneratorInterior::new(self.witness.fold_with(folder))
+    }
+
+    fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        self.witness.visit_with(visitor)
+    }
+}
+
 impl<'tcx> TypeFoldable<'tcx> for ty::adjustment::Adjustment<'tcx> {
     fn super_fold_with<'gcx: 'tcx, F: TypeFolder<'gcx, 'tcx>>(&self, folder: &mut F) -> Self {
         ty::adjustment::Adjustment {
@@ -996,12 +1051,6 @@ impl<'tcx> TypeFoldable<'tcx> for ty::error::TypeError<'tcx> {
             RegionsDoesNotOutlive(a, b) => {
                 RegionsDoesNotOutlive(a.fold_with(folder), b.fold_with(folder))
             },
-            RegionsNotSame(a, b) => {
-                RegionsNotSame(a.fold_with(folder), b.fold_with(folder))
-            },
-            RegionsNoOverlap(a, b) => {
-                RegionsNoOverlap(a.fold_with(folder), b.fold_with(folder))
-            },
             RegionsInsufficientlyPolymorphic(a, b) => {
                 RegionsInsufficientlyPolymorphic(a, b.fold_with(folder))
             },
@@ -1027,9 +1076,7 @@ impl<'tcx> TypeFoldable<'tcx> for ty::error::TypeError<'tcx> {
         match *self {
             UnsafetyMismatch(x) => x.visit_with(visitor),
             AbiMismatch(x) => x.visit_with(visitor),
-            RegionsDoesNotOutlive(a, b) |
-            RegionsNotSame(a, b) |
-            RegionsNoOverlap(a, b) => {
+            RegionsDoesNotOutlive(a, b) => {
                 a.visit_with(visitor) || b.visit_with(visitor)
             },
             RegionsInsufficientlyPolymorphic(_, b) |
diff --git a/src/librustc/ty/sty.rs b/src/librustc/ty/sty.rs
index 8d6b7b7ac9fdd..fc244cabcd11c 100644
--- a/src/librustc/ty/sty.rs
+++ b/src/librustc/ty/sty.rs
@@ -135,6 +135,10 @@ pub enum TypeVariants<'tcx> {
     /// `|a| a`.
     TyClosure(DefId, ClosureSubsts<'tcx>),
 
+    /// The anonymous type of a generator. Used to represent the type of
+    /// `|a| yield a`.
+    TyGenerator(DefId, ClosureSubsts<'tcx>, GeneratorInterior<'tcx>),
+
     /// The never type `!`
     TyNever,
 
@@ -209,8 +213,8 @@ pub enum TypeVariants<'tcx> {
 /// as extra type parameters? The reason for this design is that the
 /// upvar types can reference lifetimes that are internal to the
 /// creating function. In my example above, for example, the lifetime
-/// `'b` represents the extent of the closure itself; this is some
-/// subset of `foo`, probably just the extent of the call to the to
+/// `'b` represents the scope of the closure itself; this is some
+/// subset of `foo`, probably just the scope of the call to the to
 /// `do()`. If we just had the lifetime/type parameters from the
 /// enclosing function, we couldn't name this lifetime `'b`. Note that
 /// there can also be lifetimes in the types of the upvars themselves,
@@ -261,6 +265,51 @@ impl<'a, 'gcx, 'acx, 'tcx> ClosureSubsts<'tcx> {
     }
 }
 
+impl<'a, 'gcx, 'tcx> ClosureSubsts<'tcx> {
+    /// This returns the types of the MIR locals which had to be stored across suspension points.
+    /// It is calculated in rustc_mir::transform::generator::StateTransform.
+    /// All the types here must be in the tuple in GeneratorInterior.
+    pub fn state_tys(self, def_id: DefId, tcx: TyCtxt<'a, 'gcx, 'tcx>) ->
+        impl Iterator<Item=Ty<'tcx>> + 'a
+    {
+        let state = tcx.generator_layout(def_id).fields.iter();
+        state.map(move |d| d.ty.subst(tcx, self.substs))
+    }
+
+    /// This is the types of all the fields stored in a generator.
+    /// It includes the upvars, state types and the state discriminant which is u32.
+    pub fn field_tys(self, def_id: DefId, tcx: TyCtxt<'a, 'gcx, 'tcx>) ->
+        impl Iterator<Item=Ty<'tcx>> + 'a
+    {
+        let upvars = self.upvar_tys(def_id, tcx);
+        let state = self.state_tys(def_id, tcx);
+        upvars.chain(iter::once(tcx.types.u32)).chain(state)
+    }
+}
+
+/// This describes the types that can be contained in a generator.
+/// It will be a type variable initially and unified in the last stages of typeck of a body.
+/// It contains a tuple of all the types that could end up on a generator frame.
+/// The state transformation MIR pass may only produce layouts which mention types in this tuple.
+/// Upvars are not counted here.
+#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
+pub struct GeneratorInterior<'tcx> {
+    pub witness: Ty<'tcx>,
+}
+
+impl<'tcx> GeneratorInterior<'tcx> {
+    pub fn new(witness: Ty<'tcx>) -> GeneratorInterior<'tcx> {
+        GeneratorInterior { witness }
+    }
+
+    pub fn as_slice(&self) -> &'tcx Slice<Ty<'tcx>> {
+        match self.witness.sty {
+            ty::TyTuple(s, _) => s,
+            _ => bug!(),
+        }
+    }
+}
+
 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
 pub enum ExistentialPredicate<'tcx> {
     /// e.g. Iterator
@@ -579,6 +628,22 @@ impl<'a, 'tcx> ProjectionTy<'tcx> {
     }
 }
 
+#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
+pub struct GenSig<'tcx> {
+    pub yield_ty: Ty<'tcx>,
+    pub return_ty: Ty<'tcx>,
+}
+
+pub type PolyGenSig<'tcx> = Binder<GenSig<'tcx>>;
+
+impl<'tcx> PolyGenSig<'tcx> {
+    pub fn yield_ty(&self) -> ty::Binder<Ty<'tcx>> {
+        self.map_bound_ref(|sig| sig.yield_ty)
+    }
+    pub fn return_ty(&self) -> ty::Binder<Ty<'tcx>> {
+        self.map_bound_ref(|sig| sig.return_ty)
+    }
+}
 
 /// Signature of a function type, which I have arbitrarily
 /// decided to use to refer to the input/output types.
@@ -780,10 +845,10 @@ pub enum RegionKind {
     /// region parameters.
     ReFree(FreeRegion),
 
-    /// A concrete region naming some statically determined extent
+    /// A concrete region naming some statically determined scope
     /// (e.g. an expression or sequence of statements) within the
     /// current function.
-    ReScope(region::CodeExtent),
+    ReScope(region::Scope),
 
     /// Static data that has an "infinite" lifetime. Top in the region lattice.
     ReStatic,
@@ -1379,7 +1444,7 @@ impl<'a, 'gcx, 'tcx> TyS<'tcx> {
             TyAdt(_, substs) | TyAnon(_, substs) => {
                 substs.regions().collect()
             }
-            TyClosure(_, ref substs) => {
+            TyClosure(_, ref substs) | TyGenerator(_, ref substs, _) => {
                 substs.substs.regions().collect()
             }
             TyProjection(ref data) => {
diff --git a/src/librustc/ty/util.rs b/src/librustc/ty/util.rs
index bbbb8611f98a5..4e4c7b107c429 100644
--- a/src/librustc/ty/util.rs
+++ b/src/librustc/ty/util.rs
@@ -27,6 +27,7 @@ use rustc_data_structures::stable_hasher::{StableHasher, StableHasherResult,
                                            HashStable};
 use rustc_data_structures::fx::FxHashMap;
 use std::cmp;
+use std::iter;
 use std::hash::Hash;
 use std::intrinsics;
 use syntax::ast::{self, Name};
@@ -573,6 +574,12 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
                 }).collect()
             }
 
+            ty::TyGenerator(def_id, substs, interior) => {
+                substs.upvar_tys(def_id, self).chain(iter::once(interior.witness)).map(|ty| {
+                    self.dtorck_constraint_for_ty(span, for_ty, depth+1, ty)
+                }).collect()
+            }
+
             ty::TyAdt(def, substs) => {
                 let ty::DtorckConstraint {
                     dtorck_types, outlives
@@ -694,6 +701,7 @@ impl<'a, 'gcx, 'tcx, W> TypeVisitor<'tcx> for TypeIdHasher<'a, 'gcx, 'tcx, W>
             TyRawPtr(m) |
             TyRef(_, m) => self.hash(m.mutbl),
             TyClosure(def_id, _) |
+            TyGenerator(def_id, _, _) |
             TyAnon(def_id, _) |
             TyFnDef(def_id, _) => self.def_id(def_id),
             TyAdt(d, _) => self.def_id(d.did),
@@ -1120,6 +1128,11 @@ fn needs_drop_raw<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 
         ty::TyClosure(def_id, ref substs) => substs.upvar_tys(def_id, tcx).any(needs_drop),
 
+        // Pessimistically assume that all generators will require destructors
+        // as we don't know if a destructor is a noop or not until after the MIR
+        // state transformation pass
+        ty::TyGenerator(..) => true,
+
         ty::TyTuple(ref tys, _) => tys.iter().cloned().any(needs_drop),
 
         // unions don't have destructors regardless of the child types
diff --git a/src/librustc/ty/walk.rs b/src/librustc/ty/walk.rs
index a7f0bafe9b67d..bfabacdb17214 100644
--- a/src/librustc/ty/walk.rs
+++ b/src/librustc/ty/walk.rs
@@ -112,6 +112,10 @@ fn push_subtypes<'tcx>(stack: &mut TypeWalkerStack<'tcx>, parent_ty: Ty<'tcx>) {
         ty::TyClosure(_, ref substs) => {
             stack.extend(substs.substs.types().rev());
         }
+        ty::TyGenerator(_, ref substs, ref interior) => {
+            stack.extend(substs.substs.types().rev());
+            stack.push(interior.witness);
+        }
         ty::TyTuple(ts, _) => {
             stack.extend(ts.iter().cloned().rev());
         }
diff --git a/src/librustc/ty/wf.rs b/src/librustc/ty/wf.rs
index 6d9e648452fd3..3516f7dfb25b0 100644
--- a/src/librustc/ty/wf.rs
+++ b/src/librustc/ty/wf.rs
@@ -281,8 +281,8 @@ impl<'a, 'gcx, 'tcx> WfPredicates<'a, 'gcx, 'tcx> {
                     }
                 }
 
-                ty::TyClosure(..) => {
-                    // the types in a closure are always the types of
+                ty::TyGenerator(..) | ty::TyClosure(..) => {
+                    // the types in a closure or generator are always the types of
                     // local variables (or possibly references to local
                     // variables), we'll walk those.
                     //
diff --git a/src/librustc/util/ppaux.rs b/src/librustc/util/ppaux.rs
index 184fd75135e47..cc581b07de5fc 100644
--- a/src/librustc/util/ppaux.rs
+++ b/src/librustc/util/ppaux.rs
@@ -8,16 +8,15 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use hir::BodyId;
 use hir::def_id::DefId;
 use hir::map::definitions::DefPathData;
-use middle::region::{CodeExtent, BlockRemainder};
+use middle::region::{self, BlockRemainder};
 use ty::subst::{self, Subst};
 use ty::{BrAnon, BrEnv, BrFresh, BrNamed};
 use ty::{TyBool, TyChar, TyAdt};
 use ty::{TyError, TyStr, TyArray, TySlice, TyFloat, TyFnDef, TyFnPtr};
 use ty::{TyParam, TyRawPtr, TyRef, TyNever, TyTuple};
-use ty::{TyClosure, TyProjection, TyAnon};
+use ty::{TyClosure, TyGenerator, TyProjection, TyAnon};
 use ty::{TyDynamic, TyInt, TyUint, TyInfer};
 use ty::{self, Ty, TyCtxt, TypeFoldable};
 
@@ -525,18 +524,18 @@ impl fmt::Display for ty::RegionKind {
             ty::ReSkolemized(_, br) => {
                 write!(f, "{}", br)
             }
-            ty::ReScope(code_extent) if identify_regions() => {
-                match code_extent {
-                    CodeExtent::Misc(node_id) =>
-                        write!(f, "'{}mce", node_id.as_u32()),
-                    CodeExtent::CallSiteScope(BodyId { node_id }) =>
-                        write!(f, "'{}cce", node_id.as_u32()),
-                    CodeExtent::ParameterScope(BodyId { node_id }) =>
-                        write!(f, "'{}pce", node_id.as_u32()),
-                    CodeExtent::DestructionScope(node_id) =>
-                        write!(f, "'{}dce", node_id.as_u32()),
-                    CodeExtent::Remainder(BlockRemainder { block, first_statement_index }) =>
-                        write!(f, "'{}_{}rce", block, first_statement_index),
+            ty::ReScope(scope) if identify_regions() => {
+                match scope {
+                    region::Scope::Node(id) =>
+                        write!(f, "'{}s", id.as_usize()),
+                    region::Scope::CallSite(id) =>
+                        write!(f, "'{}cs", id.as_usize()),
+                    region::Scope::Arguments(id) =>
+                        write!(f, "'{}as", id.as_usize()),
+                    region::Scope::Destruction(id) =>
+                        write!(f, "'{}ds", id.as_usize()),
+                    region::Scope::Remainder(BlockRemainder { block, first_statement_index }) =>
+                        write!(f, "'{}_{}rs", block.as_usize(), first_statement_index),
                 }
             }
             ty::ReVar(region_vid) if identify_regions() => {
@@ -715,6 +714,12 @@ impl<'tcx> fmt::Display for ty::TraitRef<'tcx> {
     }
 }
 
+impl<'tcx> fmt::Display for ty::GeneratorInterior<'tcx> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        self.witness.fmt(f)
+    }
+}
+
 impl<'tcx> fmt::Display for ty::TypeVariants<'tcx> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         match *self {
@@ -813,6 +818,41 @@ impl<'tcx> fmt::Display for ty::TypeVariants<'tcx> {
                 })
             }
             TyStr => write!(f, "str"),
+            TyGenerator(did, substs, interior) => ty::tls::with(|tcx| {
+                let upvar_tys = substs.upvar_tys(did, tcx);
+                write!(f, "[generator")?;
+
+                if let Some(node_id) = tcx.hir.as_local_node_id(did) {
+                    write!(f, "@{:?}", tcx.hir.span(node_id))?;
+                    let mut sep = " ";
+                    tcx.with_freevars(node_id, |freevars| {
+                        for (freevar, upvar_ty) in freevars.iter().zip(upvar_tys) {
+                            let def_id = freevar.def.def_id();
+                            let node_id = tcx.hir.as_local_node_id(def_id).unwrap();
+                            write!(f,
+                                        "{}{}:{}",
+                                        sep,
+                                        tcx.local_var_name_str(node_id),
+                                        upvar_ty)?;
+                            sep = ", ";
+                        }
+                        Ok(())
+                    })?
+                } else {
+                    // cross-crate closure types should only be
+                    // visible in trans bug reports, I imagine.
+                    write!(f, "@{:?}", did)?;
+                    let mut sep = " ";
+                    for (index, upvar_ty) in upvar_tys.enumerate() {
+                        write!(f, "{}{}:{}", sep, index, upvar_ty)?;
+                        sep = ", ";
+                    }
+                }
+
+                write!(f, " {}", interior)?;
+
+                write!(f, "]")
+            }),
             TyClosure(did, substs) => ty::tls::with(|tcx| {
                 let upvar_tys = substs.upvar_tys(did, tcx);
                 write!(f, "[closure")?;
diff --git a/src/librustc_allocator/expand.rs b/src/librustc_allocator/expand.rs
index f99c6a29ff00a..eafb4c5c80078 100644
--- a/src/librustc_allocator/expand.rs
+++ b/src/librustc_allocator/expand.rs
@@ -82,10 +82,7 @@ impl<'a> Folder for ExpandAllocatorDirectives<'a> {
                 allow_internal_unsafe: false,
             }
         });
-        let span = Span {
-            ctxt: SyntaxContext::empty().apply_mark(mark),
-            ..item.span
-        };
+        let span = item.span.with_ctxt(SyntaxContext::empty().apply_mark(mark));
         let ecfg = ExpansionConfig::default(name.to_string());
         let mut f = AllocFnFactory {
             span,
diff --git a/src/librustc_borrowck/borrowck/check_loans.rs b/src/librustc_borrowck/borrowck/check_loans.rs
index 4058f3198afb4..985257c28104c 100644
--- a/src/librustc_borrowck/borrowck/check_loans.rs
+++ b/src/librustc_borrowck/borrowck/check_loans.rs
@@ -103,7 +103,8 @@ impl<'a, 'tcx> euv::Delegate<'tcx> for CheckLoanCtxt<'a, 'tcx> {
         debug!("consume(consume_id={}, cmt={:?}, mode={:?})",
                consume_id, cmt, mode);
 
-        self.consume_common(consume_id, consume_span, cmt, mode);
+        let hir_id = self.tcx().hir.node_to_hir_id(consume_id);
+        self.consume_common(hir_id.local_id, consume_span, cmt, mode);
     }
 
     fn matched_pat(&mut self,
@@ -120,7 +121,7 @@ impl<'a, 'tcx> euv::Delegate<'tcx> for CheckLoanCtxt<'a, 'tcx> {
                cmt,
                mode);
 
-        self.consume_common(consume_pat.id, consume_pat.span, cmt, mode);
+        self.consume_common(consume_pat.hir_id.local_id, consume_pat.span, cmt, mode);
     }
 
     fn borrow(&mut self,
@@ -136,15 +137,16 @@ impl<'a, 'tcx> euv::Delegate<'tcx> for CheckLoanCtxt<'a, 'tcx> {
                borrow_id, cmt, loan_region,
                bk, loan_cause);
 
+        let hir_id = self.tcx().hir.node_to_hir_id(borrow_id);
         if let Some(lp) = opt_loan_path(&cmt) {
             let moved_value_use_kind = match loan_cause {
                 euv::ClosureCapture(_) => MovedInCapture,
                 _ => MovedInUse,
             };
-            self.check_if_path_is_moved(borrow_id, borrow_span, moved_value_use_kind, &lp);
+            self.check_if_path_is_moved(hir_id.local_id, borrow_span, moved_value_use_kind, &lp);
         }
 
-        self.check_for_conflicting_loans(borrow_id);
+        self.check_for_conflicting_loans(hir_id.local_id);
     }
 
     fn mutate(&mut self,
@@ -163,7 +165,8 @@ impl<'a, 'tcx> euv::Delegate<'tcx> for CheckLoanCtxt<'a, 'tcx> {
                     // have to be *FULLY* initialized, but we still
                     // must be careful lest it contains derefs of
                     // pointers.
-                    self.check_if_assigned_path_is_moved(assignee_cmt.id,
+                    let hir_id = self.tcx().hir.node_to_hir_id(assignee_cmt.id);
+                    self.check_if_assigned_path_is_moved(hir_id.local_id,
                                                          assignment_span,
                                                          MovedInUse,
                                                          &lp);
@@ -172,14 +175,16 @@ impl<'a, 'tcx> euv::Delegate<'tcx> for CheckLoanCtxt<'a, 'tcx> {
                     // In a case like `path += 1`, then path must be
                     // fully initialized, since we will read it before
                     // we write it.
-                    self.check_if_path_is_moved(assignee_cmt.id,
+                    let hir_id = self.tcx().hir.node_to_hir_id(assignee_cmt.id);
+                    self.check_if_path_is_moved(hir_id.local_id,
                                                 assignment_span,
                                                 MovedInUse,
                                                 &lp);
                 }
             }
         }
-        self.check_assignment(assignment_id, assignment_span, assignee_cmt);
+        self.check_assignment(self.tcx().hir.node_to_hir_id(assignment_id).local_id,
+                              assignment_span, assignee_cmt);
     }
 
     fn decl_without_init(&mut self, _id: ast::NodeId, _span: Span) { }
@@ -201,7 +206,7 @@ pub fn check_loans<'a, 'b, 'c, 'tcx>(bccx: &BorrowckCtxt<'a, 'tcx>,
         all_loans,
         param_env,
     };
-    euv::ExprUseVisitor::new(&mut clcx, bccx.tcx, param_env, &bccx.region_maps, bccx.tables)
+    euv::ExprUseVisitor::new(&mut clcx, bccx.tcx, param_env, &bccx.region_scope_tree, bccx.tables)
         .consume_body(body);
 }
 
@@ -220,7 +225,7 @@ fn compatible_borrow_kinds(borrow_kind1: ty::BorrowKind,
 impl<'a, 'tcx> CheckLoanCtxt<'a, 'tcx> {
     pub fn tcx(&self) -> TyCtxt<'a, 'tcx, 'tcx> { self.bccx.tcx }
 
-    pub fn each_issued_loan<F>(&self, node: ast::NodeId, mut op: F) -> bool where
+    pub fn each_issued_loan<F>(&self, node: hir::ItemLocalId, mut op: F) -> bool where
         F: FnMut(&Loan<'tcx>) -> bool,
     {
         //! Iterates over each loan that has been issued
@@ -235,14 +240,14 @@ impl<'a, 'tcx> CheckLoanCtxt<'a, 'tcx> {
         })
     }
 
-    pub fn each_in_scope_loan<F>(&self, scope: region::CodeExtent, mut op: F) -> bool where
+    pub fn each_in_scope_loan<F>(&self, scope: region::Scope, mut op: F) -> bool where
         F: FnMut(&Loan<'tcx>) -> bool,
     {
         //! Like `each_issued_loan()`, but only considers loans that are
         //! currently in scope.
 
-        self.each_issued_loan(scope.node_id(), |loan| {
-            if self.bccx.region_maps.is_subscope_of(scope, loan.kill_scope) {
+        self.each_issued_loan(scope.item_local_id(), |loan| {
+            if self.bccx.region_scope_tree.is_subscope_of(scope, loan.kill_scope) {
                 op(loan)
             } else {
                 true
@@ -251,7 +256,7 @@ impl<'a, 'tcx> CheckLoanCtxt<'a, 'tcx> {
     }
 
     fn each_in_scope_loan_affecting_path<F>(&self,
-                                            scope: region::CodeExtent,
+                                            scope: region::Scope,
                                             loan_path: &LoanPath<'tcx>,
                                             mut op: F)
                                             -> bool where
@@ -325,7 +330,7 @@ impl<'a, 'tcx> CheckLoanCtxt<'a, 'tcx> {
         return true;
     }
 
-    pub fn loans_generated_by(&self, node: ast::NodeId) -> Vec<usize> {
+    pub fn loans_generated_by(&self, node: hir::ItemLocalId) -> Vec<usize> {
         //! Returns a vector of the loans that are generated as
         //! we enter `node`.
 
@@ -337,7 +342,7 @@ impl<'a, 'tcx> CheckLoanCtxt<'a, 'tcx> {
         return result;
     }
 
-    pub fn check_for_conflicting_loans(&self, node: ast::NodeId) {
+    pub fn check_for_conflicting_loans(&self, node: hir::ItemLocalId) {
         //! Checks to see whether any of the loans that are issued
         //! on entrance to `node` conflict with loans that have already been
         //! issued when we enter `node` (for example, we do not
@@ -381,7 +386,7 @@ impl<'a, 'tcx> CheckLoanCtxt<'a, 'tcx> {
                new_loan);
 
         // Should only be called for loans that are in scope at the same time.
-        assert!(self.bccx.region_maps.scopes_intersect(old_loan.kill_scope,
+        assert!(self.bccx.region_scope_tree.scopes_intersect(old_loan.kill_scope,
                                                        new_loan.kill_scope));
 
         self.report_error_if_loan_conflicts_with_restriction(
@@ -462,7 +467,7 @@ impl<'a, 'tcx> CheckLoanCtxt<'a, 'tcx> {
             // 3. Where does old loan expire.
 
             let previous_end_span =
-                self.tcx().hir.span(old_loan.kill_scope.node_id()).end_point();
+                old_loan.kill_scope.span(self.tcx(), &self.bccx.region_scope_tree).end_point();
 
             let mut err = match (new_loan.kind, old_loan.kind) {
                 (ty::MutBorrow, ty::MutBorrow) => {
@@ -590,7 +595,7 @@ impl<'a, 'tcx> CheckLoanCtxt<'a, 'tcx> {
     }
 
     fn consume_common(&self,
-                      id: ast::NodeId,
+                      id: hir::ItemLocalId,
                       span: Span,
                       cmt: mc::cmt<'tcx>,
                       mode: euv::ConsumeMode) {
@@ -628,7 +633,7 @@ impl<'a, 'tcx> CheckLoanCtxt<'a, 'tcx> {
     }
 
     fn check_for_copy_of_frozen_path(&self,
-                                     id: ast::NodeId,
+                                     id: hir::ItemLocalId,
                                      span: Span,
                                      copy_path: &LoanPath<'tcx>) {
         match self.analyze_restrictions_on_use(id, copy_path, ty::ImmBorrow) {
@@ -649,7 +654,7 @@ impl<'a, 'tcx> CheckLoanCtxt<'a, 'tcx> {
     }
 
     fn check_for_move_of_borrowed_path(&self,
-                                       id: ast::NodeId,
+                                       id: hir::ItemLocalId,
                                        span: Span,
                                        move_path: &LoanPath<'tcx>,
                                        move_kind: move_data::MoveKind) {
@@ -699,18 +704,17 @@ impl<'a, 'tcx> CheckLoanCtxt<'a, 'tcx> {
     }
 
     pub fn analyze_restrictions_on_use(&self,
-                                       expr_id: ast::NodeId,
+                                       expr_id: hir::ItemLocalId,
                                        use_path: &LoanPath<'tcx>,
                                        borrow_kind: ty::BorrowKind)
                                        -> UseError<'tcx> {
-        debug!("analyze_restrictions_on_use(expr_id={}, use_path={:?})",
-               self.tcx().hir.node_to_string(expr_id),
-               use_path);
+        debug!("analyze_restrictions_on_use(expr_id={:?}, use_path={:?})",
+               expr_id, use_path);
 
         let mut ret = UseOk;
 
         self.each_in_scope_loan_affecting_path(
-            region::CodeExtent::Misc(expr_id), use_path, |loan| {
+            region::Scope::Node(expr_id), use_path, |loan| {
             if !compatible_borrow_kinds(loan.kind, borrow_kind) {
                 ret = UseWhileBorrowed(loan.loan_path.clone(), loan.span);
                 false
@@ -725,11 +729,11 @@ impl<'a, 'tcx> CheckLoanCtxt<'a, 'tcx> {
     /// Reports an error if `expr` (which should be a path)
     /// is using a moved/uninitialized value
     fn check_if_path_is_moved(&self,
-                              id: ast::NodeId,
+                              id: hir::ItemLocalId,
                               span: Span,
                               use_kind: MovedValueUseKind,
                               lp: &Rc<LoanPath<'tcx>>) {
-        debug!("check_if_path_is_moved(id={}, use_kind={:?}, lp={:?})",
+        debug!("check_if_path_is_moved(id={:?}, use_kind={:?}, lp={:?})",
                id, use_kind, lp);
 
         // FIXME (22079): if you find yourself tempted to cut and paste
@@ -772,7 +776,7 @@ impl<'a, 'tcx> CheckLoanCtxt<'a, 'tcx> {
     /// (*p).x = 22; // not ok, p is uninitialized, can't deref
     /// ```
     fn check_if_assigned_path_is_moved(&self,
-                                       id: ast::NodeId,
+                                       id: hir::ItemLocalId,
                                        span: Span,
                                        use_kind: MovedValueUseKind,
                                        lp: &Rc<LoanPath<'tcx>>)
@@ -822,14 +826,14 @@ impl<'a, 'tcx> CheckLoanCtxt<'a, 'tcx> {
     }
 
     fn check_assignment(&self,
-                        assignment_id: ast::NodeId,
+                        assignment_id: hir::ItemLocalId,
                         assignment_span: Span,
                         assignee_cmt: mc::cmt<'tcx>) {
         debug!("check_assignment(assignee_cmt={:?})", assignee_cmt);
 
         // Check that we don't invalidate any outstanding loans
         if let Some(loan_path) = opt_loan_path(&assignee_cmt) {
-            let scope = region::CodeExtent::Misc(assignment_id);
+            let scope = region::Scope::Node(assignment_id);
             self.each_in_scope_loan_affecting_path(scope, &loan_path, |loan| {
                 self.report_illegal_mutation(assignment_span, &loan_path, loan);
                 false
diff --git a/src/librustc_borrowck/borrowck/gather_loans/gather_moves.rs b/src/librustc_borrowck/borrowck/gather_loans/gather_moves.rs
index 7878762788905..465457f5ab39a 100644
--- a/src/librustc_borrowck/borrowck/gather_loans/gather_moves.rs
+++ b/src/librustc_borrowck/borrowck/gather_loans/gather_moves.rs
@@ -27,7 +27,7 @@ use rustc::hir::*;
 use rustc::hir::map::Node::*;
 
 struct GatherMoveInfo<'tcx> {
-    id: ast::NodeId,
+    id: hir::ItemLocalId,
     kind: MoveKind,
     cmt: mc::cmt<'tcx>,
     span_path_opt: Option<MovePlace<'tcx>>
@@ -79,13 +79,14 @@ pub fn gather_decl<'a, 'tcx>(bccx: &BorrowckCtxt<'a, 'tcx>,
                              var_id: ast::NodeId,
                              var_ty: Ty<'tcx>) {
     let loan_path = Rc::new(LoanPath::new(LpVar(var_id), var_ty));
-    move_data.add_move(bccx.tcx, loan_path, var_id, Declared);
+    let hir_id = bccx.tcx.hir.node_to_hir_id(var_id);
+    move_data.add_move(bccx.tcx, loan_path, hir_id.local_id, Declared);
 }
 
 pub fn gather_move_from_expr<'a, 'tcx>(bccx: &BorrowckCtxt<'a, 'tcx>,
                                        move_data: &MoveData<'tcx>,
                                        move_error_collector: &mut MoveErrorCollector<'tcx>,
-                                       move_expr_id: ast::NodeId,
+                                       move_expr_id: hir::ItemLocalId,
                                        cmt: mc::cmt<'tcx>,
                                        move_reason: euv::MoveReason) {
     let kind = match move_reason {
@@ -118,7 +119,7 @@ pub fn gather_move_from_pat<'a, 'tcx>(bccx: &BorrowckCtxt<'a, 'tcx>,
         _ => None,
     };
     let move_info = GatherMoveInfo {
-        id: move_pat.id,
+        id: move_pat.hir_id.local_id,
         kind: MovePat,
         cmt,
         span_path_opt: pat_span_path_opt,
@@ -135,7 +136,7 @@ fn gather_move<'a, 'tcx>(bccx: &BorrowckCtxt<'a, 'tcx>,
                          move_data: &MoveData<'tcx>,
                          move_error_collector: &mut MoveErrorCollector<'tcx>,
                          move_info: GatherMoveInfo<'tcx>) {
-    debug!("gather_move(move_id={}, cmt={:?})",
+    debug!("gather_move(move_id={:?}, cmt={:?})",
            move_info.id, move_info.cmt);
 
     let potentially_illegal_move =
@@ -161,10 +162,10 @@ fn gather_move<'a, 'tcx>(bccx: &BorrowckCtxt<'a, 'tcx>,
 
 pub fn gather_assignment<'a, 'tcx>(bccx: &BorrowckCtxt<'a, 'tcx>,
                                    move_data: &MoveData<'tcx>,
-                                   assignment_id: ast::NodeId,
+                                   assignment_id: hir::ItemLocalId,
                                    assignment_span: Span,
                                    assignee_loan_path: Rc<LoanPath<'tcx>>,
-                                   assignee_id: ast::NodeId,
+                                   assignee_id: hir::ItemLocalId,
                                    mode: euv::MutateMode) {
     move_data.add_assignment(bccx.tcx,
                              assignee_loan_path,
diff --git a/src/librustc_borrowck/borrowck/gather_loans/lifetime.rs b/src/librustc_borrowck/borrowck/gather_loans/lifetime.rs
index 22de3c759139d..66aaafb77f757 100644
--- a/src/librustc_borrowck/borrowck/gather_loans/lifetime.rs
+++ b/src/librustc_borrowck/borrowck/gather_loans/lifetime.rs
@@ -24,7 +24,7 @@ use syntax_pos::Span;
 type R = Result<(),()>;
 
 pub fn guarantee_lifetime<'a, 'tcx>(bccx: &BorrowckCtxt<'a, 'tcx>,
-                                    item_scope: region::CodeExtent,
+                                    item_scope: region::Scope,
                                     span: Span,
                                     cause: euv::LoanCause,
                                     cmt: mc::cmt<'tcx>,
@@ -52,7 +52,7 @@ struct GuaranteeLifetimeContext<'a, 'tcx: 'a> {
     bccx: &'a BorrowckCtxt<'a, 'tcx>,
 
     // the scope of the function body for the enclosing item
-    item_scope: region::CodeExtent,
+    item_scope: region::Scope,
 
     span: Span,
     cause: euv::LoanCause,
@@ -115,8 +115,9 @@ impl<'a, 'tcx> GuaranteeLifetimeContext<'a, 'tcx> {
                 self.bccx.tcx.mk_region(ty::ReScope(self.item_scope))
             }
             Categorization::Local(local_id) => {
+                let hir_id = self.bccx.tcx.hir.node_to_hir_id(local_id);
                 self.bccx.tcx.mk_region(ty::ReScope(
-                    self.bccx.region_maps.var_scope(local_id)))
+                    self.bccx.region_scope_tree.var_scope(hir_id.local_id)))
             }
             Categorization::StaticItem |
             Categorization::Deref(_, mc::UnsafePtr(..)) => {
diff --git a/src/librustc_borrowck/borrowck/gather_loans/mod.rs b/src/librustc_borrowck/borrowck/gather_loans/mod.rs
index 00ebf5de44af8..00edd9cb28a0d 100644
--- a/src/librustc_borrowck/borrowck/gather_loans/mod.rs
+++ b/src/librustc_borrowck/borrowck/gather_loans/mod.rs
@@ -43,14 +43,13 @@ pub fn gather_loans_in_fn<'a, 'tcx>(bccx: &BorrowckCtxt<'a, 'tcx>,
     let mut glcx = GatherLoanCtxt {
         bccx,
         all_loans: Vec::new(),
-        item_ub: region::CodeExtent::Misc(body.node_id),
-        move_data: MoveData::new(),
+        item_ub: region::Scope::Node(bccx.tcx.hir.body(body).value.hir_id.local_id),
+        move_data: MoveData::default(),
         move_error_collector: move_error::MoveErrorCollector::new(),
     };
 
-    let body = glcx.bccx.tcx.hir.body(body);
-    euv::ExprUseVisitor::new(&mut glcx, bccx.tcx, param_env, &bccx.region_maps, bccx.tables)
-        .consume_body(body);
+    euv::ExprUseVisitor::new(&mut glcx, bccx.tcx, param_env, &bccx.region_scope_tree, bccx.tables)
+        .consume_body(bccx.body);
 
     glcx.report_potential_errors();
     let GatherLoanCtxt { all_loans, move_data, .. } = glcx;
@@ -64,7 +63,7 @@ struct GatherLoanCtxt<'a, 'tcx: 'a> {
     all_loans: Vec<Loan<'tcx>>,
     /// `item_ub` is used as an upper-bound on the lifetime whenever we
     /// ask for the scope of an expression categorized as an upvar.
-    item_ub: region::CodeExtent,
+    item_ub: region::Scope,
 }
 
 impl<'a, 'tcx> euv::Delegate<'tcx> for GatherLoanCtxt<'a, 'tcx> {
@@ -80,7 +79,7 @@ impl<'a, 'tcx> euv::Delegate<'tcx> for GatherLoanCtxt<'a, 'tcx> {
             euv::Move(move_reason) => {
                 gather_moves::gather_move_from_expr(
                     self.bccx, &self.move_data, &mut self.move_error_collector,
-                    consume_id, cmt, move_reason);
+                    self.bccx.tcx.hir.node_to_hir_id(consume_id).local_id, cmt, move_reason);
             }
             euv::Copy => { }
         }
@@ -127,8 +126,8 @@ impl<'a, 'tcx> euv::Delegate<'tcx> for GatherLoanCtxt<'a, 'tcx> {
                bk={:?}, loan_cause={:?})",
                borrow_id, cmt, loan_region,
                bk, loan_cause);
-
-        self.guarantee_valid(borrow_id,
+        let hir_id = self.bccx.tcx.hir.node_to_hir_id(borrow_id);
+        self.guarantee_valid(hir_id.local_id,
                              borrow_span,
                              cmt,
                              bk,
@@ -274,8 +273,12 @@ impl<'a, 'tcx> GatherLoanCtxt<'a, 'tcx> {
                     self.mark_loan_path_as_mutated(&lp);
                 }
                 gather_moves::gather_assignment(self.bccx, &self.move_data,
-                                                assignment_id, assignment_span,
-                                                lp, cmt.id, mode);
+                                                self.bccx.tcx.hir.node_to_hir_id(assignment_id)
+                                                    .local_id,
+                                                assignment_span,
+                                                lp,
+                                                self.bccx.tcx.hir.node_to_hir_id(cmt.id).local_id,
+                                                mode);
             }
             None => {
                 // This can occur with e.g. `*foo() = 5`.  In such
@@ -289,13 +292,13 @@ impl<'a, 'tcx> GatherLoanCtxt<'a, 'tcx> {
     /// reports an error.  This may entail taking out loans, which will be added to the
     /// `req_loan_map`.
     fn guarantee_valid(&mut self,
-                       borrow_id: ast::NodeId,
+                       borrow_id: hir::ItemLocalId,
                        borrow_span: Span,
                        cmt: mc::cmt<'tcx>,
                        req_kind: ty::BorrowKind,
                        loan_region: ty::Region<'tcx>,
                        cause: euv::LoanCause) {
-        debug!("guarantee_valid(borrow_id={}, cmt={:?}, \
+        debug!("guarantee_valid(borrow_id={:?}, cmt={:?}, \
                 req_mutbl={:?}, loan_region={:?})",
                borrow_id,
                cmt,
@@ -348,11 +351,11 @@ impl<'a, 'tcx> GatherLoanCtxt<'a, 'tcx> {
                     ty::ReScope(scope) => scope,
 
                     ty::ReEarlyBound(ref br) => {
-                        self.bccx.region_maps.early_free_extent(self.tcx(), br)
+                        self.bccx.region_scope_tree.early_free_scope(self.tcx(), br)
                     }
 
                     ty::ReFree(ref fr) => {
-                        self.bccx.region_maps.free_extent(self.tcx(), fr)
+                        self.bccx.region_scope_tree.free_scope(self.tcx(), fr)
                     }
 
                     ty::ReStatic => self.item_ub,
@@ -370,7 +373,7 @@ impl<'a, 'tcx> GatherLoanCtxt<'a, 'tcx> {
                 };
                 debug!("loan_scope = {:?}", loan_scope);
 
-                let borrow_scope = region::CodeExtent::Misc(borrow_id);
+                let borrow_scope = region::Scope::Node(borrow_id);
                 let gen_scope = self.compute_gen_scope(borrow_scope, loan_scope);
                 debug!("gen_scope = {:?}", gen_scope);
 
@@ -394,7 +397,7 @@ impl<'a, 'tcx> GatherLoanCtxt<'a, 'tcx> {
             }
         };
 
-        debug!("guarantee_valid(borrow_id={}), loan={:?}",
+        debug!("guarantee_valid(borrow_id={:?}), loan={:?}",
                borrow_id, loan);
 
         // let loan_path = loan.loan_path;
@@ -470,23 +473,23 @@ impl<'a, 'tcx> GatherLoanCtxt<'a, 'tcx> {
     }
 
     pub fn compute_gen_scope(&self,
-                             borrow_scope: region::CodeExtent,
-                             loan_scope: region::CodeExtent)
-                             -> region::CodeExtent {
+                             borrow_scope: region::Scope,
+                             loan_scope: region::Scope)
+                             -> region::Scope {
         //! Determine when to introduce the loan. Typically the loan
         //! is introduced at the point of the borrow, but in some cases,
         //! notably method arguments, the loan may be introduced only
         //! later, once it comes into scope.
 
-        if self.bccx.region_maps.is_subscope_of(borrow_scope, loan_scope) {
+        if self.bccx.region_scope_tree.is_subscope_of(borrow_scope, loan_scope) {
             borrow_scope
         } else {
             loan_scope
         }
     }
 
-    pub fn compute_kill_scope(&self, loan_scope: region::CodeExtent, lp: &LoanPath<'tcx>)
-                              -> region::CodeExtent {
+    pub fn compute_kill_scope(&self, loan_scope: region::Scope, lp: &LoanPath<'tcx>)
+                              -> region::Scope {
         //! Determine when the loan restrictions go out of scope.
         //! This is either when the lifetime expires or when the
         //! local variable which roots the loan-path goes out of scope,
@@ -509,10 +512,10 @@ impl<'a, 'tcx> GatherLoanCtxt<'a, 'tcx> {
         //! do not require restrictions and hence do not cause a loan.
 
         let lexical_scope = lp.kill_scope(self.bccx);
-        if self.bccx.region_maps.is_subscope_of(lexical_scope, loan_scope) {
+        if self.bccx.region_scope_tree.is_subscope_of(lexical_scope, loan_scope) {
             lexical_scope
         } else {
-            assert!(self.bccx.region_maps.is_subscope_of(loan_scope, lexical_scope));
+            assert!(self.bccx.region_scope_tree.is_subscope_of(loan_scope, lexical_scope));
             loan_scope
         }
     }
diff --git a/src/librustc_borrowck/borrowck/mod.rs b/src/librustc_borrowck/borrowck/mod.rs
index 38336655f217a..98c9a4a92ef30 100644
--- a/src/librustc_borrowck/borrowck/mod.rs
+++ b/src/librustc_borrowck/borrowck/mod.rs
@@ -32,11 +32,10 @@ use rustc::middle::expr_use_visitor as euv;
 use rustc::middle::mem_categorization as mc;
 use rustc::middle::mem_categorization::Categorization;
 use rustc::middle::mem_categorization::ImmutabilityBlame;
-use rustc::middle::region::{self, RegionMaps};
+use rustc::middle::region;
 use rustc::middle::free_region::RegionRelations;
 use rustc::ty::{self, TyCtxt};
 use rustc::ty::maps::Providers;
-
 use rustc_mir::util::borrowck_errors::{BorrowckErrors, Origin};
 
 use std::fmt;
@@ -99,10 +98,9 @@ fn borrowck<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, owner_def_id: DefId) {
 
     let body_id = tcx.hir.body_owned_by(owner_id);
     let tables = tcx.typeck_tables_of(owner_def_id);
-    let region_maps = tcx.region_maps(owner_def_id);
-    let bccx = &mut BorrowckCtxt { tcx, tables, region_maps, owner_def_id };
-
-    let body = bccx.tcx.hir.body(body_id);
+    let region_scope_tree = tcx.region_scope_tree(owner_def_id);
+    let body = tcx.hir.body(body_id);
+    let bccx = &mut BorrowckCtxt { tcx, tables, region_scope_tree, owner_def_id, body };
 
     // Eventually, borrowck will always read the MIR, but at the
     // moment we do not. So, for now, we always force MIR to be
@@ -139,10 +137,9 @@ fn build_borrowck_dataflow_data<'a, 'c, 'tcx, F>(this: &mut BorrowckCtxt<'a, 'tc
 {
     // Check the body of fn items.
     let tcx = this.tcx;
-    let body = tcx.hir.body(body_id);
     let id_range = {
         let mut visitor = intravisit::IdRangeComputingVisitor::new(&tcx.hir);
-        visitor.visit_body(body);
+        visitor.visit_body(this.body);
         visitor.result()
     };
     let (all_loans, move_data) =
@@ -163,24 +160,25 @@ fn build_borrowck_dataflow_data<'a, 'c, 'tcx, F>(this: &mut BorrowckCtxt<'a, 'tc
     let mut loan_dfcx =
         DataFlowContext::new(this.tcx,
                              "borrowck",
-                             Some(body),
+                             Some(this.body),
                              cfg,
                              LoanDataFlowOperator,
                              id_range,
                              all_loans.len());
     for (loan_idx, loan) in all_loans.iter().enumerate() {
-        loan_dfcx.add_gen(loan.gen_scope.node_id(), loan_idx);
+        loan_dfcx.add_gen(loan.gen_scope.item_local_id(), loan_idx);
         loan_dfcx.add_kill(KillFrom::ScopeEnd,
-                           loan.kill_scope.node_id(), loan_idx);
+                           loan.kill_scope.item_local_id(),
+                           loan_idx);
     }
     loan_dfcx.add_kills_from_flow_exits(cfg);
-    loan_dfcx.propagate(cfg, body);
+    loan_dfcx.propagate(cfg, this.body);
 
     let flowed_moves = move_data::FlowedMoveData::new(move_data,
                                                       this,
                                                       cfg,
                                                       id_range,
-                                                      body);
+                                                      this.body);
 
     Some(AnalysisData { all_loans,
                         loans: loan_dfcx,
@@ -198,8 +196,9 @@ pub fn build_borrowck_dataflow_data_for_fn<'a, 'tcx>(
     let owner_id = tcx.hir.body_owner(body_id);
     let owner_def_id = tcx.hir.local_def_id(owner_id);
     let tables = tcx.typeck_tables_of(owner_def_id);
-    let region_maps = tcx.region_maps(owner_def_id);
-    let mut bccx = BorrowckCtxt { tcx, tables, region_maps, owner_def_id };
+    let region_scope_tree = tcx.region_scope_tree(owner_def_id);
+    let body = tcx.hir.body(body_id);
+    let mut bccx = BorrowckCtxt { tcx, tables, region_scope_tree, owner_def_id, body };
 
     let dataflow_data = build_borrowck_dataflow_data(&mut bccx, true, body_id, |_| cfg);
     (bccx, dataflow_data.unwrap())
@@ -215,9 +214,11 @@ pub struct BorrowckCtxt<'a, 'tcx: 'a> {
     // Some in `borrowck_fn` and cleared later
     tables: &'a ty::TypeckTables<'tcx>,
 
-    region_maps: Rc<RegionMaps>,
+    region_scope_tree: Rc<region::ScopeTree>,
 
     owner_def_id: DefId,
+
+    body: &'tcx hir::Body,
 }
 
 impl<'b, 'tcx: 'b> BorrowckErrors for BorrowckCtxt<'b, 'tcx> {
@@ -254,13 +255,13 @@ pub struct Loan<'tcx> {
     /// cases, notably method arguments, the loan may be introduced
     /// only later, once it comes into scope.  See also
     /// `GatherLoanCtxt::compute_gen_scope`.
-    gen_scope: region::CodeExtent,
+    gen_scope: region::Scope,
 
     /// kill_scope indicates when the loan goes out of scope.  This is
     /// either when the lifetime expires or when the local variable
     /// which roots the loan-path goes out of scope, whichever happens
     /// faster. See also `GatherLoanCtxt::compute_kill_scope`.
-    kill_scope: region::CodeExtent,
+    kill_scope: region::Scope,
     span: Span,
     cause: euv::LoanCause,
 }
@@ -349,7 +350,7 @@ fn closure_to_block(closure_id: DefIndex,
     let closure_id = tcx.hir.def_index_to_node_id(closure_id);
     match tcx.hir.get(closure_id) {
         hir_map::NodeExpr(expr) => match expr.node {
-            hir::ExprClosure(.., body_id, _) => {
+            hir::ExprClosure(.., body_id, _, _) => {
                 body_id.node_id
             }
             _ => {
@@ -361,12 +362,16 @@ fn closure_to_block(closure_id: DefIndex,
 }
 
 impl<'a, 'tcx> LoanPath<'tcx> {
-    pub fn kill_scope(&self, bccx: &BorrowckCtxt<'a, 'tcx>) -> region::CodeExtent {
+    pub fn kill_scope(&self, bccx: &BorrowckCtxt<'a, 'tcx>) -> region::Scope {
         match self.kind {
-            LpVar(local_id) => bccx.region_maps.var_scope(local_id),
+            LpVar(local_id) => {
+                let hir_id = bccx.tcx.hir.node_to_hir_id(local_id);
+                bccx.region_scope_tree.var_scope(hir_id.local_id)
+            }
             LpUpvar(upvar_id) => {
                 let block_id = closure_to_block(upvar_id.closure_expr_id, bccx.tcx);
-                region::CodeExtent::Misc(block_id)
+                let hir_id = bccx.tcx.hir.node_to_hir_id(block_id);
+                region::Scope::Node(hir_id.local_id)
             }
             LpDowncast(ref base, _) |
             LpExtend(ref base, ..) => base.kill_scope(bccx),
@@ -530,7 +535,7 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
     {
         let region_rels = RegionRelations::new(self.tcx,
                                                self.owner_def_id,
-                                               &self.region_maps,
+                                               &self.region_scope_tree,
                                                &self.tables.free_region_map);
         region_rels.is_subregion_of(r_sub, r_sup)
     }
@@ -549,9 +554,7 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
             _ => { }
         }
 
-        let mut db = self.bckerr_to_diag(&err);
-        self.note_and_explain_bckerr(&mut db, err);
-        db.emit();
+        self.report_bckerr(&err);
     }
 
     pub fn report_use_of_moved_value(&self,
@@ -641,19 +644,22 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
 
         // Get type of value and span where it was previously
         // moved.
+        let node_id = self.tcx.hir.hir_to_node_id(hir::HirId {
+            owner: self.body.value.hir_id.owner,
+            local_id: the_move.id
+        });
         let (move_span, move_note) = match the_move.kind {
             move_data::Declared => {
                 unreachable!();
             }
 
             move_data::MoveExpr |
-            move_data::MovePat =>
-                (self.tcx.hir.span(the_move.id), ""),
+            move_data::MovePat => (self.tcx.hir.span(node_id), ""),
 
             move_data::Captured =>
-                (match self.tcx.hir.expect_expr(the_move.id).node {
-                    hir::ExprClosure(.., fn_decl_span) => fn_decl_span,
-                    ref r => bug!("Captured({}) maps to non-closure: {:?}",
+                (match self.tcx.hir.expect_expr(node_id).node {
+                    hir::ExprClosure(.., fn_decl_span, _) => fn_decl_span,
+                    ref r => bug!("Captured({:?}) maps to non-closure: {:?}",
                                   the_move.id, r),
                 }, " (into closure)"),
         };
@@ -722,8 +728,12 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
         self.tcx.sess.struct_span_err_with_code(s, msg, code)
     }
 
-    fn bckerr_to_diag(&self, err: &BckError<'tcx>) -> DiagnosticBuilder<'a> {
-        let span = err.span.clone();
+    pub fn span_err_with_code<S: Into<MultiSpan>>(&self, s: S, msg: &str, code: &str) {
+        self.tcx.sess.span_err_with_code(s, msg, code);
+    }
+
+    fn report_bckerr(&self, err: &BckError<'tcx>) {
+        let error_span = err.span.clone();
 
         match err.code {
             err_mutbl => {
@@ -747,12 +757,16 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
                     }
                 };
 
-                match err.cause {
+                let mut db = match err.cause {
                     MutabilityViolation => {
-                        struct_span_err!(self.tcx.sess, span, E0594, "cannot assign to {}", descr)
+                        struct_span_err!(self.tcx.sess,
+                                         error_span,
+                                         E0594,
+                                         "cannot assign to {}",
+                                         descr)
                     }
                     BorrowViolation(euv::ClosureCapture(_)) => {
-                        struct_span_err!(self.tcx.sess, span, E0595,
+                        struct_span_err!(self.tcx.sess, error_span, E0595,
                                          "closure cannot assign to {}", descr)
                     }
                     BorrowViolation(euv::OverloadedOperator) |
@@ -762,30 +776,238 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
                     BorrowViolation(euv::AutoUnsafe) |
                     BorrowViolation(euv::ForLoop) |
                     BorrowViolation(euv::MatchDiscriminant) => {
-                        struct_span_err!(self.tcx.sess, span, E0596,
+                        struct_span_err!(self.tcx.sess, error_span, E0596,
                                          "cannot borrow {} as mutable", descr)
                     }
                     BorrowViolation(euv::ClosureInvocation) => {
                         span_bug!(err.span,
                             "err_mutbl with a closure invocation");
                     }
-                }
+                };
+
+                self.note_and_explain_mutbl_error(&mut db, &err, &error_span);
+                self.note_immutability_blame(&mut db, err.cmt.immutability_blame());
+                db.emit();
             }
-            err_out_of_scope(..) => {
+            err_out_of_scope(super_scope, sub_scope, cause) => {
                 let msg = match opt_loan_path(&err.cmt) {
                     None => "borrowed value".to_string(),
                     Some(lp) => {
                         format!("`{}`", self.loan_path_to_string(&lp))
                     }
                 };
-                struct_span_err!(self.tcx.sess, span, E0597, "{} does not live long enough", msg)
+
+                // When you have a borrow that lives across a yield,
+                // that reference winds up captured in the generator
+                // type. Regionck then constraints it to live as long
+                // as the generator itself. If that borrow is borrowing
+                // data owned by the generator, this winds up resulting in
+                // an `err_out_of_scope` error:
+                //
+                // ```
+                // {
+                //     let g = || {
+                //         let a = &3; // this borrow is forced to ... -+
+                //         yield ();          //                        |
+                //         println!("{}", a); //                        |
+                //     };                     //                        |
+                // } <----------------------... live until here --------+
+                // ```
+                //
+                // To detect this case, we look for cases where the
+                // `super_scope` (lifetime of the value) is within the
+                // body, but the `sub_scope` is not.
+                debug!("err_out_of_scope: self.body.is_generator = {:?}",
+                       self.body.is_generator);
+                let maybe_borrow_across_yield = if self.body.is_generator {
+                    let body_scope = region::Scope::Node(self.body.value.hir_id.local_id);
+                    debug!("err_out_of_scope: body_scope = {:?}", body_scope);
+                    debug!("err_out_of_scope: super_scope = {:?}", super_scope);
+                    debug!("err_out_of_scope: sub_scope = {:?}", sub_scope);
+                    match (super_scope, sub_scope) {
+                        (&ty::RegionKind::ReScope(value_scope),
+                         &ty::RegionKind::ReScope(loan_scope)) => {
+                            if {
+                                // value_scope <= body_scope &&
+                                self.region_scope_tree.is_subscope_of(value_scope, body_scope) &&
+                                    // body_scope <= loan_scope
+                                    self.region_scope_tree.is_subscope_of(body_scope, loan_scope)
+                            } {
+                                // We now know that this is a case
+                                // that fits the bill described above:
+                                // a borrow of something whose scope
+                                // is within the generator, but the
+                                // borrow is for a scope outside the
+                                // generator.
+                                //
+                                // Now look within the scope of the of
+                                // the value being borrowed (in the
+                                // example above, that would be the
+                                // block remainder that starts with
+                                // `let a`) for a yield. We can cite
+                                // that for the user.
+                                self.region_scope_tree.yield_in_scope(value_scope)
+                            } else {
+                                None
+                            }
+                        }
+                        _ => None,
+                    }
+                } else {
+                    None
+                };
+
+                if let Some(yield_span) = maybe_borrow_across_yield {
+                    debug!("err_out_of_scope: opt_yield_span = {:?}", yield_span);
+                    struct_span_err!(self.tcx.sess,
+                                     error_span,
+                                     E0626,
+                                     "borrow may still be in use when generator yields")
+                        .span_label(yield_span, "possible yield occurs here")
+                        .emit();
+                    return;
+                }
+
+                let mut db = struct_span_err!(self.tcx.sess,
+                                              error_span,
+                                              E0597,
+                                              "{} does not live long enough",
+                                              msg);
+
+                let (value_kind, value_msg) = match err.cmt.cat {
+                    mc::Categorization::Rvalue(..) =>
+                        ("temporary value", "temporary value created here"),
+                    _ =>
+                        ("borrowed value", "borrow occurs here")
+                };
+
+                let is_closure = match cause {
+                    euv::ClosureCapture(s) => {
+                        // The primary span starts out as the closure creation point.
+                        // Change the primary span here to highlight the use of the variable
+                        // in the closure, because it seems more natural. Highlight
+                        // closure creation point as a secondary span.
+                        match db.span.primary_span() {
+                            Some(primary) => {
+                                db.span = MultiSpan::from_span(s);
+                                db.span_label(primary, "capture occurs here");
+                                db.span_label(s, "does not live long enough");
+                                true
+                            }
+                            None => false
+                        }
+                    }
+                    _ => {
+                        db.span_label(error_span, "does not live long enough");
+                        false
+                    }
+                };
+
+                let sub_span = self.region_end_span(sub_scope);
+                let super_span = self.region_end_span(super_scope);
+
+                match (sub_span, super_span) {
+                    (Some(s1), Some(s2)) if s1 == s2 => {
+                        if !is_closure {
+                            db.span = MultiSpan::from_span(s1);
+                            db.span_label(error_span, value_msg);
+                            let msg = match opt_loan_path(&err.cmt) {
+                                None => value_kind.to_string(),
+                                Some(lp) => {
+                                    format!("`{}`", self.loan_path_to_string(&lp))
+                                }
+                            };
+                            db.span_label(s1,
+                                          format!("{} dropped here while still borrowed", msg));
+                        } else {
+                            db.span_label(s1, format!("{} dropped before borrower", value_kind));
+                        }
+                        db.note("values in a scope are dropped in the opposite order \
+                                they are created");
+                    }
+                    (Some(s1), Some(s2)) if !is_closure => {
+                        db.span = MultiSpan::from_span(s2);
+                        db.span_label(error_span, value_msg);
+                        let msg = match opt_loan_path(&err.cmt) {
+                            None => value_kind.to_string(),
+                            Some(lp) => {
+                                format!("`{}`", self.loan_path_to_string(&lp))
+                            }
+                        };
+                        db.span_label(s2, format!("{} dropped here while still borrowed", msg));
+                        db.span_label(s1, format!("{} needs to live until here", value_kind));
+                    }
+                    _ => {
+                        match sub_span {
+                            Some(s) => {
+                                db.span_label(s, format!("{} needs to live until here",
+                                                          value_kind));
+                            }
+                            None => {
+                                self.tcx.note_and_explain_region(
+                                    &self.region_scope_tree,
+                                    &mut db,
+                                    "borrowed value must be valid for ",
+                                    sub_scope,
+                                    "...");
+                            }
+                        }
+                        match super_span {
+                            Some(s) => {
+                                db.span_label(s, format!("{} only lives until here", value_kind));
+                            }
+                            None => {
+                                self.tcx.note_and_explain_region(
+                                    &self.region_scope_tree,
+                                    &mut db,
+                                    "...but borrowed value is only valid for ",
+                                    super_scope,
+                                    "");
+                            }
+                        }
+                    }
+                }
+
+                if let ty::ReScope(scope) = *super_scope {
+                    let node_id = scope.node_id(self.tcx, &self.region_scope_tree);
+                    match self.tcx.hir.find(node_id) {
+                        Some(hir_map::NodeStmt(_)) => {
+                            db.note("consider using a `let` binding to increase its lifetime");
+                        }
+                        _ => {}
+                    }
+                }
+
+                db.emit();
             }
-            err_borrowed_pointer_too_short(..) => {
+            err_borrowed_pointer_too_short(loan_scope, ptr_scope) => {
                 let descr = self.cmt_to_path_or_string(&err.cmt);
-                struct_span_err!(self.tcx.sess, span, E0598,
-                                 "lifetime of {} is too short to guarantee \
-                                  its contents can be safely reborrowed",
-                                 descr)
+                let mut db = struct_span_err!(self.tcx.sess, error_span, E0598,
+                                              "lifetime of {} is too short to guarantee \
+                                               its contents can be safely reborrowed",
+                                              descr);
+
+                let descr = match opt_loan_path(&err.cmt) {
+                    Some(lp) => {
+                        format!("`{}`", self.loan_path_to_string(&lp))
+                    }
+                    None => self.cmt_to_string(&err.cmt),
+                };
+                self.tcx.note_and_explain_region(
+                    &self.region_scope_tree,
+                    &mut db,
+                    &format!("{} would have to be valid for ",
+                            descr),
+                    loan_scope,
+                    "...");
+                self.tcx.note_and_explain_region(
+                    &self.region_scope_tree,
+                    &mut db,
+                    &format!("...but {} is only valid for ", descr),
+                    ptr_scope,
+                    "");
+
+                db.emit();
             }
         }
     }
@@ -1035,146 +1257,12 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
     fn region_end_span(&self, region: ty::Region<'tcx>) -> Option<Span> {
         match *region {
             ty::ReScope(scope) => {
-                match scope.span(&self.tcx.hir) {
-                    Some(s) => {
-                        Some(s.end_point())
-                    }
-                    None => {
-                        None
-                    }
-                }
+                Some(scope.span(self.tcx, &self.region_scope_tree).end_point())
             }
             _ => None
         }
     }
 
-    fn note_and_explain_bckerr(&self, db: &mut DiagnosticBuilder, err: BckError<'tcx>) {
-        let error_span = err.span.clone();
-        match err.code {
-            err_mutbl => {
-                self.note_and_explain_mutbl_error(db, &err, &error_span);
-                self.note_immutability_blame(db, err.cmt.immutability_blame());
-            }
-            err_out_of_scope(super_scope, sub_scope, cause) => {
-                let (value_kind, value_msg) = match err.cmt.cat {
-                    mc::Categorization::Rvalue(..) =>
-                        ("temporary value", "temporary value created here"),
-                    _ =>
-                        ("borrowed value", "borrow occurs here")
-                };
-
-                let is_closure = match cause {
-                    euv::ClosureCapture(s) => {
-                        // The primary span starts out as the closure creation point.
-                        // Change the primary span here to highlight the use of the variable
-                        // in the closure, because it seems more natural. Highlight
-                        // closure creation point as a secondary span.
-                        match db.span.primary_span() {
-                            Some(primary) => {
-                                db.span = MultiSpan::from_span(s);
-                                db.span_label(primary, "capture occurs here");
-                                db.span_label(s, "does not live long enough");
-                                true
-                            }
-                            None => false
-                        }
-                    }
-                    _ => {
-                        db.span_label(error_span, "does not live long enough");
-                        false
-                    }
-                };
-
-                let sub_span = self.region_end_span(sub_scope);
-                let super_span = self.region_end_span(super_scope);
-
-                match (sub_span, super_span) {
-                    (Some(s1), Some(s2)) if s1 == s2 => {
-                        if !is_closure {
-                            db.span = MultiSpan::from_span(s1);
-                            db.span_label(error_span, value_msg);
-                            let msg = match opt_loan_path(&err.cmt) {
-                                None => value_kind.to_string(),
-                                Some(lp) => {
-                                    format!("`{}`", self.loan_path_to_string(&lp))
-                                }
-                            };
-                            db.span_label(s1,
-                                          format!("{} dropped here while still borrowed", msg));
-                        } else {
-                            db.span_label(s1, format!("{} dropped before borrower", value_kind));
-                        }
-                        db.note("values in a scope are dropped in the opposite order \
-                                they are created");
-                    }
-                    (Some(s1), Some(s2)) if !is_closure => {
-                        db.span = MultiSpan::from_span(s2);
-                        db.span_label(error_span, value_msg);
-                        let msg = match opt_loan_path(&err.cmt) {
-                            None => value_kind.to_string(),
-                            Some(lp) => {
-                                format!("`{}`", self.loan_path_to_string(&lp))
-                            }
-                        };
-                        db.span_label(s2, format!("{} dropped here while still borrowed", msg));
-                        db.span_label(s1, format!("{} needs to live until here", value_kind));
-                    }
-                    _ => {
-                        match sub_span {
-                            Some(s) => {
-                                db.span_label(s, format!("{} needs to live until here",
-                                                          value_kind));
-                            }
-                            None => {
-                                self.tcx.note_and_explain_region(
-                                    db,
-                                    "borrowed value must be valid for ",
-                                    sub_scope,
-                                    "...");
-                            }
-                        }
-                        match super_span {
-                            Some(s) => {
-                                db.span_label(s, format!("{} only lives until here", value_kind));
-                            }
-                            None => {
-                                self.tcx.note_and_explain_region(
-                                    db,
-                                    "...but borrowed value is only valid for ",
-                                    super_scope,
-                                    "");
-                            }
-                        }
-                    }
-                }
-
-                if let Some(_) = statement_scope_span(self.tcx, super_scope) {
-                    db.note("consider using a `let` binding to increase its lifetime");
-                }
-            }
-
-            err_borrowed_pointer_too_short(loan_scope, ptr_scope) => {
-                let descr = match opt_loan_path(&err.cmt) {
-                    Some(lp) => {
-                        format!("`{}`", self.loan_path_to_string(&lp))
-                    }
-                    None => self.cmt_to_string(&err.cmt),
-                };
-                self.tcx.note_and_explain_region(
-                    db,
-                    &format!("{} would have to be valid for ",
-                            descr),
-                    loan_scope,
-                    "...");
-                self.tcx.note_and_explain_region(
-                    db,
-                    &format!("...but {} is only valid for ", descr),
-                    ptr_scope,
-                    "");
-            }
-        }
-    }
-
     fn note_and_explain_mutbl_error(&self, db: &mut DiagnosticBuilder, err: &BckError<'tcx>,
                                     error_span: &Span) {
         match err.cmt.note {
@@ -1306,18 +1394,6 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
     }
 }
 
-fn statement_scope_span(tcx: TyCtxt, region: ty::Region) -> Option<Span> {
-    match *region {
-        ty::ReScope(scope) => {
-            match tcx.hir.find(scope.node_id()) {
-                Some(hir_map::NodeStmt(stmt)) => Some(stmt.span),
-                _ => None
-            }
-        }
-        _ => None
-    }
-}
-
 impl BitwiseOperator for LoanDataFlowOperator {
     #[inline]
     fn join(&self, succ: usize, pred: usize) -> usize {
diff --git a/src/librustc_borrowck/borrowck/move_data.rs b/src/librustc_borrowck/borrowck/move_data.rs
index 217bd6e6ca1ca..7915eccbf7445 100644
--- a/src/librustc_borrowck/borrowck/move_data.rs
+++ b/src/librustc_borrowck/borrowck/move_data.rs
@@ -23,16 +23,16 @@ use rustc::middle::expr_use_visitor as euv;
 use rustc::middle::expr_use_visitor::MutateMode;
 use rustc::middle::mem_categorization as mc;
 use rustc::ty::{self, TyCtxt};
-use rustc::util::nodemap::{FxHashMap, NodeSet};
+use rustc::util::nodemap::{FxHashMap, FxHashSet};
 
 use std::cell::RefCell;
 use std::rc::Rc;
 use std::usize;
-use syntax::ast;
 use syntax_pos::Span;
 use rustc::hir;
 use rustc::hir::intravisit::IdRange;
 
+#[derive(Default)]
 pub struct MoveData<'tcx> {
     /// Move paths. See section "Move paths" in `README.md`.
     pub paths: RefCell<Vec<MovePath<'tcx>>>,
@@ -54,7 +54,7 @@ pub struct MoveData<'tcx> {
     pub path_assignments: RefCell<Vec<Assignment>>,
 
     /// Assignments to a variable or path, like `x = foo`, but not `x += foo`.
-    pub assignee_ids: RefCell<NodeSet>,
+    pub assignee_ids: RefCell<FxHashSet<hir::ItemLocalId>>,
 }
 
 pub struct FlowedMoveData<'a, 'tcx: 'a> {
@@ -133,7 +133,7 @@ pub struct Move {
     pub path: MovePathIndex,
 
     /// id of node that is doing the move.
-    pub id: ast::NodeId,
+    pub id: hir::ItemLocalId,
 
     /// Kind of move, for error messages.
     pub kind: MoveKind,
@@ -148,13 +148,13 @@ pub struct Assignment {
     pub path: MovePathIndex,
 
     /// id where assignment occurs
-    pub id: ast::NodeId,
+    pub id: hir::ItemLocalId,
 
     /// span of node where assignment occurs
     pub span: Span,
 
     /// id for l-value expression on lhs of assignment
-    pub assignee_id: ast::NodeId,
+    pub assignee_id: hir::ItemLocalId,
 }
 
 #[derive(Clone, Copy)]
@@ -189,17 +189,6 @@ fn loan_path_is_precise(loan_path: &LoanPath) -> bool {
 }
 
 impl<'a, 'tcx> MoveData<'tcx> {
-    pub fn new() -> MoveData<'tcx> {
-        MoveData {
-            paths: RefCell::new(Vec::new()),
-            path_map: RefCell::new(FxHashMap()),
-            moves: RefCell::new(Vec::new()),
-            path_assignments: RefCell::new(Vec::new()),
-            var_assignments: RefCell::new(Vec::new()),
-            assignee_ids: RefCell::new(NodeSet()),
-        }
-    }
-
     /// return true if there are no trackable assignments or moves
     /// in this move data - that means that there is nothing that
     /// could cause a borrow error.
@@ -345,7 +334,7 @@ impl<'a, 'tcx> MoveData<'tcx> {
     /// Adds a new move entry for a move of `lp` that occurs at location `id` with kind `kind`.
     pub fn add_move(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>,
                     orig_lp: Rc<LoanPath<'tcx>>,
-                    id: ast::NodeId,
+                    id: hir::ItemLocalId,
                     kind: MoveKind) {
         // Moving one union field automatically moves all its fields. Also move siblings of
         // all parent union fields, moves do not propagate upwards automatically.
@@ -373,9 +362,9 @@ impl<'a, 'tcx> MoveData<'tcx> {
 
     fn add_move_helper(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>,
                        lp: Rc<LoanPath<'tcx>>,
-                       id: ast::NodeId,
+                       id: hir::ItemLocalId,
                        kind: MoveKind) {
-        debug!("add_move(lp={:?}, id={}, kind={:?})",
+        debug!("add_move(lp={:?}, id={:?}, kind={:?})",
                lp,
                id,
                kind);
@@ -398,9 +387,9 @@ impl<'a, 'tcx> MoveData<'tcx> {
     /// `span`.
     pub fn add_assignment(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>,
                           lp: Rc<LoanPath<'tcx>>,
-                          assign_id: ast::NodeId,
+                          assign_id: hir::ItemLocalId,
                           span: Span,
-                          assignee_id: ast::NodeId,
+                          assignee_id: hir::ItemLocalId,
                           mode: euv::MutateMode) {
         // Assigning to one union field automatically assigns to all its fields.
         if let LpExtend(ref base_lp, mutbl, LpInterior(opt_variant_id, interior)) = lp.kind {
@@ -429,11 +418,11 @@ impl<'a, 'tcx> MoveData<'tcx> {
 
     fn add_assignment_helper(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>,
                              lp: Rc<LoanPath<'tcx>>,
-                             assign_id: ast::NodeId,
+                             assign_id: hir::ItemLocalId,
                              span: Span,
-                             assignee_id: ast::NodeId,
+                             assignee_id: hir::ItemLocalId,
                              mode: euv::MutateMode) {
-        debug!("add_assignment(lp={:?}, assign_id={}, assignee_id={}",
+        debug!("add_assignment(lp={:?}, assign_id={:?}, assignee_id={:?}",
                lp, assign_id, assignee_id);
 
         let path_index = self.move_path(tcx, lp.clone());
@@ -496,7 +485,7 @@ impl<'a, 'tcx> MoveData<'tcx> {
                 LpVar(..) | LpUpvar(..) | LpDowncast(..) => {
                     let kill_scope = path.loan_path.kill_scope(bccx);
                     let path = *self.path_map.borrow().get(&path.loan_path).unwrap();
-                    self.kill_moves(path, kill_scope.node_id(),
+                    self.kill_moves(path, kill_scope.item_local_id(),
                                     KillFrom::ScopeEnd, dfcx_moves);
                 }
                 LpExtend(..) => {}
@@ -511,7 +500,7 @@ impl<'a, 'tcx> MoveData<'tcx> {
                 LpVar(..) | LpUpvar(..) | LpDowncast(..) => {
                     let kill_scope = lp.kill_scope(bccx);
                     dfcx_assign.add_kill(KillFrom::ScopeEnd,
-                                         kill_scope.node_id(),
+                                         kill_scope.item_local_id(),
                                          assignment_index);
                 }
                 LpExtend(..) => {
@@ -579,7 +568,7 @@ impl<'a, 'tcx> MoveData<'tcx> {
 
     fn kill_moves(&self,
                   path: MovePathIndex,
-                  kill_id: ast::NodeId,
+                  kill_id: hir::ItemLocalId,
                   kill_kind: KillFrom,
                   dfcx_moves: &mut MoveDataFlow) {
         // We can only perform kills for paths that refer to a unique location,
@@ -589,7 +578,7 @@ impl<'a, 'tcx> MoveData<'tcx> {
         let loan_path = self.path_loan_path(path);
         if loan_path_is_precise(&loan_path) {
             self.each_applicable_move(path, |move_index| {
-                debug!("kill_moves add_kill {:?} kill_id={} move_index={}",
+                debug!("kill_moves add_kill {:?} kill_id={:?} move_index={}",
                        kill_kind, kill_id, move_index.get());
                 dfcx_moves.add_kill(kill_kind, kill_id, move_index.get());
                 true
@@ -642,7 +631,7 @@ impl<'a, 'tcx> FlowedMoveData<'a, 'tcx> {
     }
 
     pub fn kind_of_move_of_path(&self,
-                                id: ast::NodeId,
+                                id: hir::ItemLocalId,
                                 loan_path: &Rc<LoanPath<'tcx>>)
                                 -> Option<MoveKind> {
         //! Returns the kind of a move of `loan_path` by `id`, if one exists.
@@ -667,7 +656,7 @@ impl<'a, 'tcx> FlowedMoveData<'a, 'tcx> {
     /// have occurred on entry to `id` without an intervening assignment. In other words, any moves
     /// that would invalidate a reference to `loan_path` at location `id`.
     pub fn each_move_of<F>(&self,
-                           id: ast::NodeId,
+                           id: hir::ItemLocalId,
                            loan_path: &Rc<LoanPath<'tcx>>,
                            mut f: F)
                            -> bool where
@@ -724,7 +713,7 @@ impl<'a, 'tcx> FlowedMoveData<'a, 'tcx> {
     /// Iterates through every assignment to `loan_path` that may have occurred on entry to `id`.
     /// `loan_path` must be a single variable.
     pub fn each_assignment_of<F>(&self,
-                                 id: ast::NodeId,
+                                 id: hir::ItemLocalId,
                                  loan_path: &Rc<LoanPath<'tcx>>,
                                  mut f: F)
                                  -> bool where
diff --git a/src/librustc_borrowck/diagnostics.rs b/src/librustc_borrowck/diagnostics.rs
index 1f1fc4cc65fbe..74133c821f0fa 100644
--- a/src/librustc_borrowck/diagnostics.rs
+++ b/src/librustc_borrowck/diagnostics.rs
@@ -652,6 +652,92 @@ x.x = Some(&y);
 ```
 "##,
 
+E0626: r##"
+This error occurs because a borrow in a generator persists across a
+yield point.
+
+```compile_fail,E0626
+# #![feature(generators, generator_trait)]
+# use std::ops::Generator;
+let mut b = || {
+    let a = &String::new(); // <-- This borrow...
+    yield (); // ...is still in scope here, when the yield occurs.
+    println!("{}", a);
+};
+b.resume();
+```
+
+At present, it is not permitted to have a yield that occurs while a
+borrow is still in scope. To resolve this error, the borrow must
+either be "contained" to a smaller scope that does not overlap the
+yield or else eliminated in another way. So, for example, we might
+resolve the previous example by removing the borrow and just storing
+the integer by value:
+
+```
+# #![feature(generators, generator_trait)]
+# use std::ops::Generator;
+let mut b = || {
+    let a = 3;
+    yield ();
+    println!("{}", a);
+};
+b.resume();
+```
+
+This is a very simple case, of course. In more complex cases, we may
+wish to have more than one reference to the value that was borrowed --
+in those cases, something like the `Rc` or `Arc` types may be useful.
+
+This error also frequently arises with iteration:
+
+```compile_fail,E0626
+# #![feature(generators, generator_trait)]
+# use std::ops::Generator;
+let mut b = || {
+  let v = vec![1,2,3];
+  for &x in &v { // <-- borrow of `v` is still in scope...
+    yield x; // ...when this yield occurs.
+  }
+};
+b.resume();
+```
+
+Such cases can sometimes be resolved by iterating "by value" (or using
+`into_iter()`) to avoid borrowing:
+
+```
+# #![feature(generators, generator_trait)]
+# use std::ops::Generator;
+let mut b = || {
+  let v = vec![1,2,3];
+  for x in v { // <-- Take ownership of the values instead!
+    yield x; // <-- Now yield is OK.
+  }
+};
+b.resume();
+```
+
+If taking ownership is not an option, using indices can work too:
+
+```
+# #![feature(generators, generator_trait)]
+# use std::ops::Generator;
+let mut b = || {
+  let v = vec![1,2,3];
+  let len = v.len(); // (*)
+  for i in 0..len {
+    let x = v[i]; // (*)
+    yield x; // <-- Now yield is OK.
+  }
+};
+b.resume();
+
+// (*) -- Unfortunately, these temporaries are currently required.
+// See <https://github.com/rust-lang/rust/issues/43122>.
+```
+"##,
+
 }
 
 register_diagnostics! {
diff --git a/src/librustc_borrowck/graphviz.rs b/src/librustc_borrowck/graphviz.rs
index e3a2bfa392738..22867ba5b55a4 100644
--- a/src/librustc_borrowck/graphviz.rs
+++ b/src/librustc_borrowck/graphviz.rs
@@ -52,7 +52,7 @@ pub struct DataflowLabeller<'a, 'tcx: 'a> {
 impl<'a, 'tcx> DataflowLabeller<'a, 'tcx> {
     fn dataflow_for(&self, e: EntryOrExit, n: &Node<'a>) -> String {
         let id = n.1.data.id();
-        debug!("dataflow_for({:?}, id={}) {:?}", e, id, self.variants);
+        debug!("dataflow_for({:?}, id={:?}) {:?}", e, id, self.variants);
         let mut sets = "".to_string();
         let mut seen_one = false;
         for &variant in &self.variants {
diff --git a/src/librustc_const_eval/check_match.rs b/src/librustc_const_eval/check_match.rs
index 2bed1950afc28..d832ad0ab1d20 100644
--- a/src/librustc_const_eval/check_match.rs
+++ b/src/librustc_const_eval/check_match.rs
@@ -18,7 +18,7 @@ use rustc::middle::expr_use_visitor::{ConsumeMode, Delegate, ExprUseVisitor};
 use rustc::middle::expr_use_visitor::{LoanCause, MutateMode};
 use rustc::middle::expr_use_visitor as euv;
 use rustc::middle::mem_categorization::{cmt};
-use rustc::middle::region::RegionMaps;
+use rustc::middle::region;
 use rustc::session::Session;
 use rustc::ty::{self, Ty, TyCtxt};
 use rustc::ty::subst::Substs;
@@ -51,7 +51,7 @@ impl<'a, 'tcx> Visitor<'tcx> for OuterVisitor<'a, 'tcx> {
         MatchVisitor {
             tcx: self.tcx,
             tables: self.tcx.body_tables(b),
-            region_maps: &self.tcx.region_maps(def_id),
+            region_scope_tree: &self.tcx.region_scope_tree(def_id),
             param_env: self.tcx.param_env(def_id),
             identity_substs: Substs::identity_for_item(self.tcx, def_id),
         }.visit_body(self.tcx.hir.body(b));
@@ -72,7 +72,7 @@ struct MatchVisitor<'a, 'tcx: 'a> {
     tables: &'a ty::TypeckTables<'tcx>,
     param_env: ty::ParamEnv<'tcx>,
     identity_substs: &'tcx Substs<'tcx>,
-    region_maps: &'a RegionMaps,
+    region_scope_tree: &'a region::ScopeTree,
 }
 
 impl<'a, 'tcx> Visitor<'tcx> for MatchVisitor<'a, 'tcx> {
@@ -526,7 +526,7 @@ fn check_for_mutation_in_guard(cx: &MatchVisitor, guard: &hir::Expr) {
     let mut checker = MutationChecker {
         cx,
     };
-    ExprUseVisitor::new(&mut checker, cx.tcx, cx.param_env, cx.region_maps, cx.tables)
+    ExprUseVisitor::new(&mut checker, cx.tcx, cx.param_env, cx.region_scope_tree, cx.tables)
         .walk_expr(guard);
 }
 
diff --git a/src/librustc_data_structures/indexed_set.rs b/src/librustc_data_structures/indexed_set.rs
index 9cb6806e9ade5..47fa21e3bf0b2 100644
--- a/src/librustc_data_structures/indexed_set.rs
+++ b/src/librustc_data_structures/indexed_set.rs
@@ -9,9 +9,11 @@
 // except according to those terms.
 
 use std::fmt;
+use std::iter;
 use std::marker::PhantomData;
 use std::mem;
 use std::ops::{Deref, DerefMut, Range};
+use std::slice;
 use bitslice::{BitSlice, Word};
 use bitslice::{bitwise, Union, Subtract};
 use indexed_vec::Idx;
@@ -21,6 +23,7 @@ use indexed_vec::Idx;
 ///
 /// In other words, `T` is the type used to index into the bitvector
 /// this type uses to represent the set of object it holds.
+#[derive(Eq, PartialEq)]
 pub struct IdxSetBuf<T: Idx> {
     _pd: PhantomData<fn(&T)>,
     bits: Vec<Word>,
@@ -109,6 +112,13 @@ impl<T: Idx> IdxSet<T> {
         }
     }
 
+    /// Removes all elements
+    pub fn clear(&mut self) {
+        for b in &mut self.bits {
+            *b = 0;
+        }
+    }
+
     /// Removes `elem` from the set `self`; returns true iff this changed `self`.
     pub fn remove(&mut self, elem: &T) -> bool {
         self.bits.clear_bit(elem.index())
@@ -154,6 +164,14 @@ impl<T: Idx> IdxSet<T> {
         bitwise(self.words_mut(), other.words(), &Subtract)
     }
 
+    pub fn iter(&self) -> Iter<T> {
+        Iter {
+            cur: None,
+            iter: self.words().iter().enumerate(),
+            _pd: PhantomData,
+        }
+    }
+
     /// Calls `f` on each index value held in this set, up to the
     /// bound `max_bits` on the size of universe of indexes.
     pub fn each_bit<F>(&self, max_bits: usize, f: F) where F: FnMut(T) {
@@ -218,3 +236,32 @@ fn each_bit<T: Idx, F>(words: &IdxSet<T>, max_bits: usize, mut f: F) where F: Fn
         }
     }
 }
+
+pub struct Iter<'a, T: Idx> {
+    cur: Option<(Word, usize)>,
+    iter: iter::Enumerate<slice::Iter<'a, Word>>,
+    _pd: PhantomData<fn(&T)>,
+}
+
+impl<'a, T: Idx> Iterator for Iter<'a, T> {
+    type Item = T;
+
+    fn next(&mut self) -> Option<T> {
+        let word_bits = mem::size_of::<Word>() * 8;
+        loop {
+            if let Some((ref mut word, offset)) = self.cur {
+                let bit_pos = word.trailing_zeros() as usize;
+                if bit_pos != word_bits {
+                    let bit = 1 << bit_pos;
+                    *word ^= bit;
+                    return Some(T::new(bit_pos + offset))
+                }
+            }
+
+            match self.iter.next() {
+                Some((i, word)) => self.cur = Some((*word, word_bits * i)),
+                None => return None,
+            }
+        }
+    }
+}
diff --git a/src/librustc_data_structures/indexed_vec.rs b/src/librustc_data_structures/indexed_vec.rs
index bc9bfa4049723..1d0e88ee32855 100644
--- a/src/librustc_data_structures/indexed_vec.rs
+++ b/src/librustc_data_structures/indexed_vec.rs
@@ -38,7 +38,7 @@ impl Idx for u32 {
     fn index(self) -> usize { self as usize }
 }
 
-#[derive(Clone)]
+#[derive(Clone, PartialEq, Eq)]
 pub struct IndexVec<I: Idx, T> {
     pub raw: Vec<T>,
     _marker: PhantomData<Fn(&I)>
diff --git a/src/librustc_data_structures/lib.rs b/src/librustc_data_structures/lib.rs
index da00ebc4b9ee9..47061883425e2 100644
--- a/src/librustc_data_structures/lib.rs
+++ b/src/librustc_data_structures/lib.rs
@@ -29,7 +29,6 @@
 #![feature(unsize)]
 #![feature(i128_type)]
 #![feature(conservative_impl_trait)]
-#![feature(discriminant_value)]
 #![feature(specialization)]
 
 #![cfg_attr(unix, feature(libc))]
diff --git a/src/librustc_data_structures/stable_hasher.rs b/src/librustc_data_structures/stable_hasher.rs
index 6801aa455e11e..33c4a041cff88 100644
--- a/src/librustc_data_structures/stable_hasher.rs
+++ b/src/librustc_data_structures/stable_hasher.rs
@@ -292,6 +292,15 @@ impl<T: HashStable<CTX>, CTX> HashStable<CTX> for Vec<T> {
     }
 }
 
+impl<T: HashStable<CTX>, CTX> HashStable<CTX> for Box<T> {
+    #[inline]
+    fn hash_stable<W: StableHasherResult>(&self,
+                                          ctx: &mut CTX,
+                                          hasher: &mut StableHasher<W>) {
+        (**self).hash_stable(ctx, hasher);
+    }
+}
+
 impl<T: HashStable<CTX>, CTX> HashStable<CTX> for ::std::rc::Rc<T> {
     #[inline]
     fn hash_stable<W: StableHasherResult>(&self,
diff --git a/src/librustc_data_structures/unify/mod.rs b/src/librustc_data_structures/unify/mod.rs
index 7853bf9478ab8..5411ae0257a4b 100644
--- a/src/librustc_data_structures/unify/mod.rs
+++ b/src/librustc_data_structures/unify/mod.rs
@@ -119,10 +119,10 @@ impl<K: UnifyKey> VarValue<K> {
     }
 }
 
-// We can't use V:LatticeValue, much as I would like to,
-// because frequently the pattern is that V=Option<U> for some
-// other type parameter U, and we have no way to say
-// Option<U>:LatticeValue.
+/// We can't use V:LatticeValue, much as I would like to,
+/// because frequently the pattern is that V=Option<U> for some
+/// other type parameter U, and we have no way to say
+/// Option<U>:LatticeValue.
 
 impl<K: UnifyKey> UnificationTable<K> {
     pub fn new() -> UnificationTable<K> {
@@ -249,7 +249,7 @@ impl<K: UnifyKey> sv::SnapshotVecDelegate for Delegate<K> {
     fn reverse(_: &mut Vec<VarValue<K>>, _: ()) {}
 }
 
-// # Base union-find algorithm, where we are just making sets
+/// # Base union-find algorithm, where we are just making sets
 
 impl<'tcx, K: UnifyKey> UnificationTable<K>
     where K::Value: Combine
@@ -281,11 +281,11 @@ impl<'tcx, K: UnifyKey> UnificationTable<K>
     }
 }
 
-// # Non-subtyping unification
-//
-// Code to handle keys which carry a value, like ints,
-// floats---anything that doesn't have a subtyping relationship we
-// need to worry about.
+/// # Non-subtyping unification
+///
+/// Code to handle keys which carry a value, like ints,
+/// floats---anything that doesn't have a subtyping relationship we
+/// need to worry about.
 
 impl<'tcx, K, V> UnificationTable<K>
     where K: UnifyKey<Value = Option<V>>,
diff --git a/src/librustc_driver/driver.rs b/src/librustc_driver/driver.rs
index 96688c6ac9cdb..000d89241a427 100644
--- a/src/librustc_driver/driver.rs
+++ b/src/librustc_driver/driver.rs
@@ -1015,6 +1015,8 @@ pub fn phase_3_run_analysis_passes<'tcx, F, R>(sess: &'tcx Session,
     passes.push_pass(MIR_OPTIMIZED, mir::transform::deaggregator::Deaggregator);
     passes.push_pass(MIR_OPTIMIZED, mir::transform::copy_prop::CopyPropagation);
     passes.push_pass(MIR_OPTIMIZED, mir::transform::simplify::SimplifyLocals);
+
+    passes.push_pass(MIR_OPTIMIZED, mir::transform::generator::StateTransform);
     passes.push_pass(MIR_OPTIMIZED, mir::transform::add_call_guards::CriticalCallEdges);
     passes.push_pass(MIR_OPTIMIZED, mir::transform::dump_mir::Marker("PreTrans"));
 
diff --git a/src/librustc_driver/lib.rs b/src/librustc_driver/lib.rs
index 1915a1c86484a..5011b53799043 100644
--- a/src/librustc_driver/lib.rs
+++ b/src/librustc_driver/lib.rs
@@ -741,7 +741,9 @@ impl RustcDefaultCalls {
                         odir: &Option<PathBuf>,
                         ofile: &Option<PathBuf>)
                         -> Compilation {
-        if sess.opts.prints.is_empty() {
+        // PrintRequest::NativeStaticLibs is special - printed during linking
+        // (empty iterator returns true)
+        if sess.opts.prints.iter().all(|&p| p==PrintRequest::NativeStaticLibs) {
             return Compilation::Continue;
         }
 
@@ -851,6 +853,9 @@ impl RustcDefaultCalls {
                 PrintRequest::TargetCPUs | PrintRequest::TargetFeatures => {
                     rustc_trans::print(*req, sess);
                 }
+                PrintRequest::NativeStaticLibs => {
+                    println!("Native static libs can be printed only during linking");
+                }
             }
         }
         return Compilation::Stop;
diff --git a/src/librustc_driver/pretty.rs b/src/librustc_driver/pretty.rs
index 20f2a146b0b15..6a58b7fb75360 100644
--- a/src/librustc_driver/pretty.rs
+++ b/src/librustc_driver/pretty.rs
@@ -765,7 +765,7 @@ fn print_flowgraph<'a, 'tcx, W: Write>(variants: Vec<borrowck_dot::Variant>,
     let cfg = cfg::CFG::new(tcx, &body);
     let labelled_edges = mode != PpFlowGraphMode::UnlabelledEdges;
     let lcfg = LabelledCFG {
-        hir_map: &tcx.hir,
+        tcx,
         cfg: &cfg,
         name: format!("node_{}", code.id()),
         labelled_edges,
diff --git a/src/librustc_driver/test.rs b/src/librustc_driver/test.rs
index b187cdaa480ed..552130e8a4703 100644
--- a/src/librustc_driver/test.rs
+++ b/src/librustc_driver/test.rs
@@ -17,7 +17,7 @@ use rustc_resolve::MakeGlobMap;
 use rustc_trans;
 use rustc::middle::lang_items;
 use rustc::middle::free_region::FreeRegionMap;
-use rustc::middle::region::{CodeExtent, RegionMaps};
+use rustc::middle::region;
 use rustc::middle::resolve_lifetime;
 use rustc::middle::stability;
 use rustc::ty::subst::{Kind, Subst};
@@ -45,12 +45,12 @@ use rustc::hir;
 
 struct Env<'a, 'gcx: 'a + 'tcx, 'tcx: 'a> {
     infcx: &'a infer::InferCtxt<'a, 'gcx, 'tcx>,
-    region_maps: &'a mut RegionMaps,
+    region_scope_tree: &'a mut region::ScopeTree,
     param_env: ty::ParamEnv<'tcx>,
 }
 
 struct RH<'a> {
-    id: ast::NodeId,
+    id: hir::ItemLocalId,
     sub: &'a [RH<'a>],
 }
 
@@ -157,15 +157,15 @@ fn test_env<F>(source_string: &str,
                              "test_crate",
                              |tcx| {
         tcx.infer_ctxt().enter(|infcx| {
-            let mut region_maps = RegionMaps::new();
+            let mut region_scope_tree = region::ScopeTree::default();
             body(Env {
                 infcx: &infcx,
-                region_maps: &mut region_maps,
+                region_scope_tree: &mut region_scope_tree,
                 param_env: ty::ParamEnv::empty(Reveal::UserFacing),
             });
             let free_regions = FreeRegionMap::new();
             let def_id = tcx.hir.local_def_id(ast::CRATE_NODE_ID);
-            infcx.resolve_regions_and_report_errors(def_id, &region_maps, &free_regions);
+            infcx.resolve_regions_and_report_errors(def_id, &region_scope_tree, &free_regions);
             assert_eq!(tcx.sess.err_count(), expected_err_count);
         });
     });
@@ -176,9 +176,9 @@ impl<'a, 'gcx, 'tcx> Env<'a, 'gcx, 'tcx> {
         self.infcx.tcx
     }
 
-    pub fn create_region_hierarchy(&mut self, rh: &RH, parent: CodeExtent) {
-        let me = CodeExtent::Misc(rh.id);
-        self.region_maps.record_code_extent(me, Some(parent));
+    pub fn create_region_hierarchy(&mut self, rh: &RH, parent: region::Scope) {
+        let me = region::Scope::Node(rh.id);
+        self.region_scope_tree.record_scope_parent(me, Some(parent));
         for child_rh in rh.sub {
             self.create_region_hierarchy(child_rh, me);
         }
@@ -188,21 +188,19 @@ impl<'a, 'gcx, 'tcx> Env<'a, 'gcx, 'tcx> {
         // creates a region hierarchy where 1 is root, 10 and 11 are
         // children of 1, etc
 
-        let node = ast::NodeId::from_u32;
-        let dscope = CodeExtent::DestructionScope(node(1));
-        self.region_maps.record_code_extent(dscope, None);
+        let dscope = region::Scope::Destruction(hir::ItemLocalId(1));
+        self.region_scope_tree.record_scope_parent(dscope, None);
         self.create_region_hierarchy(&RH {
-                                         id: node(1),
-                                         sub: &[RH {
-                                                    id: node(10),
-                                                    sub: &[],
-                                                },
-                                                RH {
-                                                    id: node(11),
-                                                    sub: &[],
-                                                }],
-                                     },
-                                     dscope);
+            id: hir::ItemLocalId(1),
+            sub: &[RH {
+                id: hir::ItemLocalId(10),
+                sub: &[],
+            },
+            RH {
+                id: hir::ItemLocalId(11),
+                sub: &[],
+            }],
+        }, dscope);
     }
 
     #[allow(dead_code)] // this seems like it could be useful, even if we don't use it now
@@ -335,7 +333,7 @@ impl<'a, 'gcx, 'tcx> Env<'a, 'gcx, 'tcx> {
     }
 
     pub fn t_rptr_scope(&self, id: u32) -> Ty<'tcx> {
-        let r = ty::ReScope(CodeExtent::Misc(ast::NodeId::from_u32(id)));
+        let r = ty::ReScope(region::Scope::Node(hir::ItemLocalId(id)));
         self.infcx.tcx.mk_imm_ref(self.infcx.tcx.mk_region(r), self.tcx().types.isize)
     }
 
diff --git a/src/librustc_errors/diagnostic.rs b/src/librustc_errors/diagnostic.rs
index 0f063542383dc..9aae188f9ecdf 100644
--- a/src/librustc_errors/diagnostic.rs
+++ b/src/librustc_errors/diagnostic.rs
@@ -288,7 +288,7 @@ impl Diagnostic {
 
     /// Convenience function for internal use, clients should use one of the
     /// public methods above.
-    fn sub(&mut self,
+    pub(crate) fn sub(&mut self,
            level: Level,
            message: &str,
            span: MultiSpan,
diff --git a/src/librustc_errors/diagnostic_builder.rs b/src/librustc_errors/diagnostic_builder.rs
index 2c8d8b4691f0a..2cd433bfe3aee 100644
--- a/src/librustc_errors/diagnostic_builder.rs
+++ b/src/librustc_errors/diagnostic_builder.rs
@@ -110,6 +110,19 @@ impl<'a> DiagnosticBuilder<'a> {
         // }
     }
 
+    /// Convenience function for internal use, clients should use one of the
+    /// span_* methods instead.
+    pub fn sub<S: Into<MultiSpan>>(
+        &mut self,
+        level: Level,
+        message: &str,
+        span: Option<S>,
+    ) -> &mut Self {
+        let span = span.map(|s| s.into()).unwrap_or(MultiSpan::new());
+        self.diagnostic.sub(level, message, span, None);
+        self
+    }
+
     /// Delay emission of this diagnostic as a bug.
     ///
     /// This can be useful in contexts where an error indicates a bug but
diff --git a/src/librustc_errors/emitter.rs b/src/librustc_errors/emitter.rs
index 53d90531cc946..daa132dbf6213 100644
--- a/src/librustc_errors/emitter.rs
+++ b/src/librustc_errors/emitter.rs
@@ -183,8 +183,8 @@ impl EmitterWriter {
                     continue;
                 }
 
-                let lo = cm.lookup_char_pos(span_label.span.lo);
-                let mut hi = cm.lookup_char_pos(span_label.span.hi);
+                let lo = cm.lookup_char_pos(span_label.span.lo());
+                let mut hi = cm.lookup_char_pos(span_label.span.hi());
 
                 // Watch out for "empty spans". If we get a span like 6..6, we
                 // want to just display a `^` at 6, so convert that to
@@ -683,7 +683,7 @@ impl EmitterWriter {
         if let Some(ref cm) = self.cm {
             for primary_span in msp.primary_spans() {
                 if primary_span != &DUMMY_SP {
-                    let hi = cm.lookup_char_pos(primary_span.hi);
+                    let hi = cm.lookup_char_pos(primary_span.hi());
                     if hi.line > max {
                         max = hi.line;
                     }
@@ -691,7 +691,7 @@ impl EmitterWriter {
             }
             for span_label in msp.span_labels() {
                 if span_label.span != DUMMY_SP {
-                    let hi = cm.lookup_char_pos(span_label.span.hi);
+                    let hi = cm.lookup_char_pos(span_label.span.hi());
                     if hi.line > max {
                         max = hi.line;
                     }
@@ -914,7 +914,7 @@ impl EmitterWriter {
         let (primary_lo, cm) = if let (Some(cm), Some(ref primary_span)) =
             (self.cm.as_ref(), msp.primary_span().as_ref()) {
             if primary_span != &&DUMMY_SP {
-                (cm.lookup_char_pos(primary_span.lo), cm)
+                (cm.lookup_char_pos(primary_span.lo()), cm)
             } else {
                 emit_to_destination(&buffer.render(), level, &mut self.dst)?;
                 return Ok(());
@@ -1091,7 +1091,7 @@ impl EmitterWriter {
                                Some(Style::HeaderMsg));
 
             let suggestions = suggestion.splice_lines(cm.borrow());
-            let span_start_pos = cm.lookup_char_pos(primary_sub.span.lo);
+            let span_start_pos = cm.lookup_char_pos(primary_sub.span.lo());
             let line_start = span_start_pos.line;
             draw_col_separator_no_space(&mut buffer, 1, max_line_num_len + 1);
             let mut row_num = 2;
diff --git a/src/librustc_errors/lib.rs b/src/librustc_errors/lib.rs
index 870bb01bb9ffb..d9b0f4ac8a6c0 100644
--- a/src/librustc_errors/lib.rs
+++ b/src/librustc_errors/lib.rs
@@ -148,16 +148,12 @@ impl CodeSuggestion {
 
         // Assumption: all spans are in the same file, and all spans
         // are disjoint. Sort in ascending order.
-        primary_spans.sort_by_key(|sp| sp.0.lo);
+        primary_spans.sort_by_key(|sp| sp.0.lo());
 
         // Find the bounding span.
-        let lo = primary_spans.iter().map(|sp| sp.0.lo).min().unwrap();
-        let hi = primary_spans.iter().map(|sp| sp.0.hi).min().unwrap();
-        let bounding_span = Span {
-            lo,
-            hi,
-            ctxt: NO_EXPANSION,
-        };
+        let lo = primary_spans.iter().map(|sp| sp.0.lo()).min().unwrap();
+        let hi = primary_spans.iter().map(|sp| sp.0.hi()).min().unwrap();
+        let bounding_span = Span::new(lo, hi, NO_EXPANSION);
         let lines = cm.span_to_lines(bounding_span).unwrap();
         assert!(!lines.lines.is_empty());
 
@@ -171,14 +167,14 @@ impl CodeSuggestion {
         //
         // Finally push the trailing line segment of the last span
         let fm = &lines.file;
-        let mut prev_hi = cm.lookup_char_pos(bounding_span.lo);
+        let mut prev_hi = cm.lookup_char_pos(bounding_span.lo());
         prev_hi.col = CharPos::from_usize(0);
 
         let mut prev_line = fm.get_line(lines.lines[0].line_index);
         let mut bufs = vec![(String::new(), false); self.substitutions()];
 
         for (sp, substitutes) in primary_spans {
-            let cur_lo = cm.lookup_char_pos(sp.lo);
+            let cur_lo = cm.lookup_char_pos(sp.lo());
             for (&mut (ref mut buf, ref mut underline), substitute) in bufs.iter_mut()
                                                                            .zip(substitutes) {
                 if prev_hi.line == cur_lo.line {
@@ -208,7 +204,7 @@ impl CodeSuggestion {
                 }
                 buf.push_str(substitute);
             }
-            prev_hi = cm.lookup_char_pos(sp.hi);
+            prev_hi = cm.lookup_char_pos(sp.hi());
             prev_line = fm.get_line(prev_hi.line - 1);
         }
         for &mut (ref mut buf, _) in &mut bufs {
@@ -306,6 +302,12 @@ impl Handler {
         self.continue_after_error.set(continue_after_error);
     }
 
+    // NOTE: DO NOT call this function from rustc, as it relies on `err_count` being non-zero
+    // if an error happened to avoid ICEs. This function should only be called from tools.
+    pub fn reset_err_count(&self) {
+        self.err_count.set(0);
+    }
+
     pub fn struct_dummy<'a>(&'a self) -> DiagnosticBuilder<'a> {
         DiagnosticBuilder::new(self, Level::Cancelled, "")
     }
diff --git a/src/librustc_lint/builtin.rs b/src/librustc_lint/builtin.rs
index 3bfe2897de175..780d34d570170 100644
--- a/src/librustc_lint/builtin.rs
+++ b/src/librustc_lint/builtin.rs
@@ -44,7 +44,7 @@ use std::collections::HashSet;
 use syntax::ast;
 use syntax::attr;
 use syntax::feature_gate::{AttributeGate, AttributeType, Stability, deprecated_attributes};
-use syntax_pos::Span;
+use syntax_pos::{Span, SyntaxContext};
 use syntax::symbol::keywords;
 
 use rustc::hir::{self, PatKind};
@@ -75,9 +75,11 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for WhileTrue {
         if let hir::ExprWhile(ref cond, ..) = e.node {
             if let hir::ExprLit(ref lit) = cond.node {
                 if let ast::LitKind::Bool(true) = lit.node {
-                    cx.span_lint(WHILE_TRUE,
-                                 e.span,
-                                 "denote infinite loops with loop { ... }");
+                    if lit.span.ctxt() == SyntaxContext::empty() {
+                        cx.span_lint(WHILE_TRUE,
+                                    e.span,
+                                    "denote infinite loops with loop { ... }");
+                    }
                 }
             }
         }
@@ -850,23 +852,25 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnconditionalRecursion {
             }
             visited.insert(cfg_id);
 
-            let node_id = cfg.graph.node_data(idx).id();
-
             // is this a recursive call?
-            let self_recursive = if node_id != ast::DUMMY_NODE_ID {
-                match method {
+            let local_id = cfg.graph.node_data(idx).id();
+            if local_id != hir::DUMMY_ITEM_LOCAL_ID {
+                let node_id = cx.tcx.hir.hir_to_node_id(hir::HirId {
+                    owner: body.value.hir_id.owner,
+                    local_id
+                });
+                let self_recursive = match method {
                     Some(ref method) => expr_refers_to_this_method(cx, method, node_id),
                     None => expr_refers_to_this_fn(cx, id, node_id),
+                };
+                if self_recursive {
+                    self_call_spans.push(cx.tcx.hir.span(node_id));
+                    // this is a self call, so we shouldn't explore past
+                    // this node in the CFG.
+                    continue;
                 }
-            } else {
-                false
-            };
-            if self_recursive {
-                self_call_spans.push(cx.tcx.hir.span(node_id));
-                // this is a self call, so we shouldn't explore past
-                // this node in the CFG.
-                continue;
             }
+
             // add the successors of this node to explore the graph further.
             for (_, edge) in cfg.graph.outgoing_edges(idx) {
                 let target_idx = edge.target();
diff --git a/src/librustc_lint/lib.rs b/src/librustc_lint/lib.rs
index 5ef277f02ace6..fbf993f45576c 100644
--- a/src/librustc_lint/lib.rs
+++ b/src/librustc_lint/lib.rs
@@ -128,7 +128,6 @@ pub fn register_builtins(store: &mut lint::LintStore, sess: Option<&Session>) {
                  NonSnakeCase,
                  NonUpperCaseGlobals,
                  NonShorthandFieldPatterns,
-                 UnusedUnsafe,
                  UnsafeCode,
                  UnusedMut,
                  UnusedAllocation,
diff --git a/src/librustc_lint/types.rs b/src/librustc_lint/types.rs
index cdf0996796085..ccd3194b5e388 100644
--- a/src/librustc_lint/types.rs
+++ b/src/librustc_lint/types.rs
@@ -543,6 +543,18 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
                            `u32` or `libc::wchar_t` should be used")
             }
 
+            ty::TyInt(ast::IntTy::I128) => {
+                FfiUnsafe("found Rust type `i128` in foreign module, but \
+                           128-bit integers don't currently have a known \
+                           stable ABI")
+            }
+
+            ty::TyUint(ast::UintTy::U128) => {
+                FfiUnsafe("found Rust type `u128` in foreign module, but \
+                           128-bit integers don't currently have a known \
+                           stable ABI")
+            }
+
             // Primitive types with a stable representation.
             ty::TyBool | ty::TyInt(..) | ty::TyUint(..) | ty::TyFloat(..) | ty::TyNever => FfiSafe,
 
@@ -607,6 +619,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
             ty::TyInfer(..) |
             ty::TyError |
             ty::TyClosure(..) |
+            ty::TyGenerator(..) |
             ty::TyProjection(..) |
             ty::TyAnon(..) |
             ty::TyFnDef(..) => bug!("Unexpected type in foreign function"),
diff --git a/src/librustc_lint/unused.rs b/src/librustc_lint/unused.rs
index cbc4ebe90fd09..15efc14b061f0 100644
--- a/src/librustc_lint/unused.rs
+++ b/src/librustc_lint/unused.rs
@@ -204,60 +204,6 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedResults {
     }
 }
 
-declare_lint! {
-    pub UNUSED_UNSAFE,
-    Warn,
-    "unnecessary use of an `unsafe` block"
-}
-
-#[derive(Copy, Clone)]
-pub struct UnusedUnsafe;
-
-impl LintPass for UnusedUnsafe {
-    fn get_lints(&self) -> LintArray {
-        lint_array!(UNUSED_UNSAFE)
-    }
-}
-
-impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedUnsafe {
-    fn check_expr(&mut self, cx: &LateContext, e: &hir::Expr) {
-        /// Return the NodeId for an enclosing scope that is also `unsafe`
-        fn is_enclosed(cx: &LateContext, id: ast::NodeId) -> Option<(String, ast::NodeId)> {
-            let parent_id = cx.tcx.hir.get_parent_node(id);
-            if parent_id != id {
-                if cx.tcx.used_unsafe.borrow().contains(&parent_id) {
-                    Some(("block".to_string(), parent_id))
-                } else if let Some(hir::map::NodeItem(&hir::Item {
-                    node: hir::ItemFn(_, hir::Unsafety::Unsafe, _, _, _, _),
-                    ..
-                })) = cx.tcx.hir.find(parent_id) {
-                    Some(("fn".to_string(), parent_id))
-                } else {
-                    is_enclosed(cx, parent_id)
-                }
-            } else {
-                None
-            }
-        }
-        if let hir::ExprBlock(ref blk) = e.node {
-            // Don't warn about generated blocks, that'll just pollute the output.
-            if blk.rules == hir::UnsafeBlock(hir::UserProvided) &&
-               !cx.tcx.used_unsafe.borrow().contains(&blk.id) {
-
-                let mut db = cx.struct_span_lint(UNUSED_UNSAFE, blk.span,
-                                                 "unnecessary `unsafe` block");
-
-                db.span_label(blk.span, "unnecessary `unsafe` block");
-                if let Some((kind, id)) = is_enclosed(cx, blk.id) {
-                    db.span_note(cx.tcx.hir.span(id),
-                                 &format!("because it's nested under this `unsafe` {}", kind));
-                }
-                db.emit();
-            }
-        }
-    }
-}
-
 declare_lint! {
     pub PATH_STATEMENTS,
     Warn,
diff --git a/src/librustc_metadata/cstore_impl.rs b/src/librustc_metadata/cstore_impl.rs
index ad320a7ff3d1e..537e12086141c 100644
--- a/src/librustc_metadata/cstore_impl.rs
+++ b/src/librustc_metadata/cstore_impl.rs
@@ -38,6 +38,7 @@ use syntax::ext::base::SyntaxExtension;
 use syntax::parse::filemap_to_stream;
 use syntax::symbol::Symbol;
 use syntax_pos::{Span, NO_EXPANSION};
+use rustc_data_structures::indexed_set::IdxSetBuf;
 use rustc::hir::svh::Svh;
 use rustc::hir;
 
@@ -105,7 +106,10 @@ provide! { <'tcx> tcx, def_id, cdata,
 
         mir
     }
-    mir_const_qualif => { cdata.mir_const_qualif(def_id.index) }
+    generator_sig => { cdata.generator_sig(def_id.index, tcx) }
+    mir_const_qualif => {
+        (cdata.mir_const_qualif(def_id.index), Rc::new(IdxSetBuf::new_empty(0)))
+    }
     typeck_tables_of => { cdata.item_body_tables(def_id.index, tcx) }
     closure_kind => { cdata.closure_kind(def_id.index) }
     fn_sig => { cdata.fn_sig(def_id.index, tcx) }
@@ -368,7 +372,7 @@ impl CrateStore for cstore::CStore {
         let source_name = format!("<{} macros>", name);
 
         let filemap = sess.parse_sess.codemap().new_filemap(source_name, def.body);
-        let local_span = Span { lo: filemap.start_pos, hi: filemap.end_pos, ctxt: NO_EXPANSION };
+        let local_span = Span::new(filemap.start_pos, filemap.end_pos, NO_EXPANSION);
         let body = filemap_to_stream(&sess.parse_sess, filemap, None);
 
         // Mark the attrs as used
diff --git a/src/librustc_metadata/decoder.rs b/src/librustc_metadata/decoder.rs
index 73b2e972b93ca..1e2f167f19962 100644
--- a/src/librustc_metadata/decoder.rs
+++ b/src/librustc_metadata/decoder.rs
@@ -242,7 +242,7 @@ impl<'a, 'tcx> SpecializedDecoder<Span> for DecodeContext<'a, 'tcx> {
         let sess = if let Some(sess) = self.sess {
             sess
         } else {
-            return Ok(Span { lo: lo, hi: hi, ctxt: NO_EXPANSION });
+            return Ok(Span::new(lo, hi, NO_EXPANSION));
         };
 
         let (lo, hi) = if lo > hi {
@@ -289,7 +289,7 @@ impl<'a, 'tcx> SpecializedDecoder<Span> for DecodeContext<'a, 'tcx> {
         let lo = (lo - filemap.original_start_pos) + filemap.translated_filemap.start_pos;
         let hi = (hi - filemap.original_start_pos) + filemap.translated_filemap.start_pos;
 
-        Ok(Span { lo: lo, hi: hi, ctxt: NO_EXPANSION })
+        Ok(Span::new(lo, hi, NO_EXPANSION))
     }
 }
 
@@ -438,6 +438,7 @@ impl<'tcx> EntryKind<'tcx> {
             EntryKind::Impl(_) |
             EntryKind::DefaultImpl(_) |
             EntryKind::Field |
+            EntryKind::Generator(_) |
             EntryKind::Closure(_) => return None,
         })
     }
@@ -1100,6 +1101,23 @@ impl<'a, 'tcx> CrateMetadata {
         sig.decode((self, tcx))
     }
 
+    fn get_generator_data(&self,
+                      id: DefIndex,
+                      tcx: TyCtxt<'a, 'tcx, 'tcx>)
+                      -> Option<GeneratorData<'tcx>> {
+        match self.entry(id).kind {
+            EntryKind::Generator(data) => Some(data.decode((self, tcx))),
+            _ => None,
+        }
+    }
+
+    pub fn generator_sig(&self,
+                      id: DefIndex,
+                      tcx: TyCtxt<'a, 'tcx, 'tcx>)
+                      -> Option<ty::PolyGenSig<'tcx>> {
+        self.get_generator_data(id, tcx).map(|d| d.sig)
+    }
+
     #[inline]
     pub fn def_key(&self, index: DefIndex) -> DefKey {
         self.def_path_table.def_key(index)
diff --git a/src/librustc_metadata/encoder.rs b/src/librustc_metadata/encoder.rs
index 1dc5d695348c1..d36aebe38eb0b 100644
--- a/src/librustc_metadata/encoder.rs
+++ b/src/librustc_metadata/encoder.rs
@@ -548,12 +548,13 @@ impl<'a, 'b: 'a, 'tcx: 'b> IsolatedEncoder<'a, 'b, 'tcx> {
                                                                  &hir::Visibility)>)
                            -> Entry<'tcx> {
         let tcx = self.tcx;
+        let hir_id = tcx.hir.node_to_hir_id(id);
         let def_id = tcx.hir.local_def_id(id);
         debug!("IsolatedEncoder::encode_info_for_mod({:?})", def_id);
 
         let data = ModData {
-            reexports: match tcx.export_map.get(&id) {
-                Some(exports) if *vis == hir::Public => {
+            reexports: match tcx.module_exports(hir_id) {
+                Some(ref exports) if *vis == hir::Public => {
                     self.lazy_seq_from_slice(exports.as_slice())
                 }
                 _ => LazySeq::empty(),
@@ -792,7 +793,7 @@ impl<'a, 'b: 'a, 'tcx: 'b> IsolatedEncoder<'a, 'b, 'tcx> {
         let kind = match impl_item.kind {
             ty::AssociatedKind::Const => {
                 EntryKind::AssociatedConst(container,
-                    self.tcx.at(ast_item.span).mir_const_qualif(def_id))
+                    self.tcx.at(ast_item.span).mir_const_qualif(def_id).0)
             }
             ty::AssociatedKind::Method => {
                 let fn_data = if let hir::ImplItemKind::Method(ref sig, body) = ast_item.node {
@@ -911,7 +912,7 @@ impl<'a, 'b: 'a, 'tcx: 'b> IsolatedEncoder<'a, 'b, 'tcx> {
             hir::ItemStatic(_, hir::MutMutable, _) => EntryKind::MutStatic,
             hir::ItemStatic(_, hir::MutImmutable, _) => EntryKind::ImmStatic,
             hir::ItemConst(..) => {
-                EntryKind::Const(tcx.at(item.span).mir_const_qualif(def_id))
+                EntryKind::Const(tcx.at(item.span).mir_const_qualif(def_id).0)
             }
             hir::ItemFn(_, _, constness, .., body) => {
                 let data = FnData {
@@ -1213,13 +1214,23 @@ impl<'a, 'b: 'a, 'tcx: 'b> IsolatedEncoder<'a, 'b, 'tcx> {
         debug!("IsolatedEncoder::encode_info_for_closure({:?})", def_id);
         let tcx = self.tcx;
 
-        let data = ClosureData {
-            kind: tcx.closure_kind(def_id),
-            sig: self.lazy(&tcx.fn_sig(def_id)),
+        let kind = if let Some(sig) = self.tcx.generator_sig(def_id) {
+            let layout = self.tcx.generator_layout(def_id);
+            let data = GeneratorData {
+                sig,
+                layout: layout.clone(),
+            };
+            EntryKind::Generator(self.lazy(&data))
+        } else {
+            let data = ClosureData {
+                kind: tcx.closure_kind(def_id),
+                sig: self.lazy(&tcx.fn_sig(def_id)),
+            };
+            EntryKind::Closure(self.lazy(&data))
         };
 
         Entry {
-            kind: EntryKind::Closure(self.lazy(&data)),
+            kind,
             visibility: self.lazy(&ty::Visibility::Public),
             span: self.lazy(&tcx.def_span(def_id)),
             attributes: self.encode_attributes(&tcx.get_attrs(def_id)),
@@ -1245,7 +1256,7 @@ impl<'a, 'b: 'a, 'tcx: 'b> IsolatedEncoder<'a, 'b, 'tcx> {
         let body = tcx.hir.body_owned_by(id);
 
         Entry {
-            kind: EntryKind::Const(tcx.mir_const_qualif(def_id)),
+            kind: EntryKind::Const(tcx.mir_const_qualif(def_id).0),
             visibility: self.lazy(&ty::Visibility::Public),
             span: self.lazy(&tcx.def_span(def_id)),
             attributes: LazySeq::empty(),
diff --git a/src/librustc_metadata/lib.rs b/src/librustc_metadata/lib.rs
index f79abecf9da4b..f4e6f57c43777 100644
--- a/src/librustc_metadata/lib.rs
+++ b/src/librustc_metadata/lib.rs
@@ -21,7 +21,6 @@
 #![feature(quote)]
 #![feature(rustc_diagnostic_macros)]
 #![feature(specialization)]
-#![feature(discriminant_value)]
 #![feature(rustc_private)]
 
 #[macro_use]
diff --git a/src/librustc_metadata/schema.rs b/src/librustc_metadata/schema.rs
index b71f4d0d98cf9..d065a0fc21c6c 100644
--- a/src/librustc_metadata/schema.rs
+++ b/src/librustc_metadata/schema.rs
@@ -353,6 +353,7 @@ pub enum EntryKind<'tcx> {
     Mod(Lazy<ModData>),
     MacroDef(Lazy<MacroDef>),
     Closure(Lazy<ClosureData<'tcx>>),
+    Generator(Lazy<GeneratorData<'tcx>>),
     Trait(Lazy<TraitData<'tcx>>),
     Impl(Lazy<ImplData<'tcx>>),
     DefaultImpl(Lazy<ImplData<'tcx>>),
@@ -401,6 +402,9 @@ impl<'a, 'gcx, 'tcx> HashStable<StableHashingContext<'a, 'gcx, 'tcx>> for EntryK
             EntryKind::MacroDef(ref macro_def) => {
                 macro_def.hash_stable(hcx, hasher);
             }
+            EntryKind::Generator(data) => {
+                data.hash_stable(hcx, hasher);
+            }
             EntryKind::Closure(closure_data) => {
                 closure_data.hash_stable(hcx, hasher);
             }
@@ -564,3 +568,10 @@ pub struct ClosureData<'tcx> {
     pub sig: Lazy<ty::PolyFnSig<'tcx>>,
 }
 impl_stable_hash_for!(struct ClosureData<'tcx> { kind, sig });
+
+#[derive(RustcEncodable, RustcDecodable)]
+pub struct GeneratorData<'tcx> {
+    pub sig: ty::PolyGenSig<'tcx>,
+    pub layout: mir::GeneratorLayout<'tcx>,
+}
+impl_stable_hash_for!(struct GeneratorData<'tcx> { sig, layout });
diff --git a/src/librustc_mir/borrow_check.rs b/src/librustc_mir/borrow_check.rs
index eda2bacb11fdc..063cbc7755915 100644
--- a/src/librustc_mir/borrow_check.rs
+++ b/src/librustc_mir/borrow_check.rs
@@ -212,11 +212,11 @@ impl<'c, 'b, 'a: 'b+'c, 'gcx, 'tcx: 'a> DataflowResultsConsumer<'b, 'gcx>
                 // ignored by borrowck
             }
 
-            StatementKind::StorageDead(ref lvalue) => {
+            StatementKind::StorageDead(local) => {
                 // causes non-drop values to be dropped.
                 self.consume_lvalue(ContextKind::StorageDead.new(location),
                                     ConsumeKind::Consume,
-                                    (lvalue, span),
+                                    (&Lvalue::Local(local), span),
                                     flow_state)
             }
         }
@@ -279,12 +279,20 @@ impl<'c, 'b, 'a: 'b+'c, 'gcx, 'tcx: 'a> DataflowResultsConsumer<'b, 'gcx>
                                              (index, span), flow_state);
                     }
                     AssertMessage::Math(_/*const_math_err*/) => {}
+                    AssertMessage::GeneratorResumedAfterReturn => {}
+                    AssertMessage::GeneratorResumedAfterPanic => {}
                 }
             }
 
+            TerminatorKind::Yield { ref value, resume: _, drop: _} => {
+                self.consume_operand(ContextKind::Yield.new(loc),
+                                     Consume, (value, span), flow_state);
+            }
+
             TerminatorKind::Goto { target: _ } |
             TerminatorKind::Resume |
             TerminatorKind::Return |
+            TerminatorKind::GeneratorDrop |
             TerminatorKind::Unreachable => {
                 // no data used, thus irrelevant to borrowck
             }
@@ -595,7 +603,7 @@ impl<'c, 'b, 'a: 'b+'c, 'gcx, 'tcx: 'a> MirBorrowckCtxt<'c, 'b, 'a, 'gcx, 'tcx>
         //
         // (Or if you prefer, all the *other* iterations over loans
         // only consider loans that are in scope of some given
-        // CodeExtent)
+        // region::Scope)
         //
         // The (currently skeletal) code here does not encode such a
         // distinction, which means it is almost certainly over
@@ -702,7 +710,7 @@ mod restrictions {
 
     use rustc::hir;
     use rustc::ty::{self, TyCtxt};
-    use rustc::mir::{Lvalue, Mir, Operand, ProjectionElem};
+    use rustc::mir::{Lvalue, Mir, ProjectionElem};
 
     pub(super) struct Restrictions<'c, 'tcx: 'c> {
         mir: &'c Mir<'tcx>,
@@ -801,12 +809,7 @@ mod restrictions {
                         ProjectionElem::Downcast(..) |
                         ProjectionElem::Subslice { .. } |
                         ProjectionElem::ConstantIndex { .. } |
-                        ProjectionElem::Index(Operand::Constant(..)) => {
-                            cursor = &proj.base;
-                            continue 'cursor;
-                        }
-                        ProjectionElem::Index(Operand::Consume(ref index)) => {
-                            self.lvalue_stack.push(index); // FIXME: did old borrowck do this?
+                        ProjectionElem::Index(_) => {
                             cursor = &proj.base;
                             continue 'cursor;
                         }
@@ -996,7 +999,7 @@ impl<'c, 'b, 'a: 'b+'c, 'gcx, 'tcx: 'a> MirBorrowckCtxt<'c, 'b, 'a, 'gcx, 'tcx>
                         ("",   format!(""), None), // (dont emit downcast info)
                     ProjectionElem::Field(field, _ty) =>
                         ("",   format!(".{}", field.index()), None),
-                    ProjectionElem::Index(ref index) =>
+                    ProjectionElem::Index(index) =>
                         ("",   format!(""), Some(index)),
                     ProjectionElem::ConstantIndex { offset, min_length, from_end: true } =>
                         ("",   format!("[{} of {}]", offset, min_length), None),
@@ -1013,23 +1016,11 @@ impl<'c, 'b, 'a: 'b+'c, 'gcx, 'tcx: 'a> MirBorrowckCtxt<'c, 'b, 'a, 'gcx, 'tcx>
                 self.append_lvalue_to_string(&proj.base, buf);
                 if let Some(index) = index_operand {
                     buf.push_str("[");
-                    self.append_operand_to_string(index, buf);
+                    self.append_lvalue_to_string(&Lvalue::Local(index), buf);
                     buf.push_str("]");
                 } else {
                     buf.push_str(&suffix);
                 }
-
-            }
-        }
-    }
-
-    fn append_operand_to_string(&self, operand: &Operand, buf: &mut String) {
-        match *operand {
-            Operand::Consume(ref lvalue) => {
-                self.append_lvalue_to_string(lvalue, buf);
-            }
-            Operand::Constant(ref constant) => {
-                buf.push_str(&format!("{:?}", constant));
             }
         }
     }
@@ -1102,6 +1093,7 @@ enum ContextKind {
     CallDest,
     Assert,
     StorageDead,
+    Yield,
 }
 
 impl ContextKind {
diff --git a/src/librustc_mir/build/block.rs b/src/librustc_mir/build/block.rs
index 4583d80b83ddc..0e412fb27ca68 100644
--- a/src/librustc_mir/build/block.rs
+++ b/src/librustc_mir/build/block.rs
@@ -21,10 +21,10 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                      ast_block: &'tcx hir::Block,
                      source_info: SourceInfo)
                      -> BlockAnd<()> {
-        let Block { extent, opt_destruction_extent, span, stmts, expr, targeted_by_break } =
+        let Block { region_scope, opt_destruction_scope, span, stmts, expr, targeted_by_break } =
             self.hir.mirror(ast_block);
-        self.in_opt_scope(opt_destruction_extent.map(|de|(de, source_info)), block, move |this| {
-            this.in_scope((extent, source_info), block, move |this| {
+        self.in_opt_scope(opt_destruction_scope.map(|de|(de, source_info)), block, move |this| {
+            this.in_scope((region_scope, source_info), block, move |this| {
                 if targeted_by_break {
                     // This is a `break`-able block (currently only `catch { ... }`)
                     let exit_block = this.cfg.start_new_block();
@@ -67,15 +67,15 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
         // the let-scopes at the end.
         //
         // First we build all the statements in the block.
-        let mut let_extent_stack = Vec::with_capacity(8);
+        let mut let_scope_stack = Vec::with_capacity(8);
         let outer_visibility_scope = this.visibility_scope;
         let source_info = this.source_info(span);
         for stmt in stmts {
-            let Stmt { span, kind, opt_destruction_extent } = this.hir.mirror(stmt);
+            let Stmt { kind, opt_destruction_scope } = this.hir.mirror(stmt);
             match kind {
                 StmtKind::Expr { scope, expr } => {
                     unpack!(block = this.in_opt_scope(
-                        opt_destruction_extent.map(|de|(de, source_info)), block, |this| {
+                        opt_destruction_scope.map(|de|(de, source_info)), block, |this| {
                             this.in_scope((scope, source_info), block, |this| {
                                 let expr = this.hir.mirror(expr);
                                 this.stmt_expr(block, expr)
@@ -83,21 +83,19 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                         }));
                 }
                 StmtKind::Let { remainder_scope, init_scope, pattern, initializer } => {
-                    let tcx = this.hir.tcx();
-
                     // Enter the remainder scope, i.e. the bindings' destruction scope.
                     this.push_scope((remainder_scope, source_info));
-                    let_extent_stack.push(remainder_scope);
+                    let_scope_stack.push(remainder_scope);
 
                     // Declare the bindings, which may create a visibility scope.
-                    let remainder_span = remainder_scope.span(&tcx.hir);
-                    let remainder_span = remainder_span.unwrap_or(span);
+                    let remainder_span = remainder_scope.span(this.hir.tcx(),
+                                                              &this.hir.region_scope_tree);
                     let scope = this.declare_bindings(None, remainder_span, &pattern);
 
                     // Evaluate the initializer, if present.
                     if let Some(init) = initializer {
                         unpack!(block = this.in_opt_scope(
-                            opt_destruction_extent.map(|de|(de, source_info)), block, move |this| {
+                            opt_destruction_scope.map(|de|(de, source_info)), block, move |this| {
                                 this.in_scope((init_scope, source_info), block, move |this| {
                                     // FIXME #30046                             ^~~~
                                     this.expr_into_pattern(block, pattern, init)
@@ -126,8 +124,8 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
         }
         // Finally, we pop all the let scopes before exiting out from the scope of block
         // itself.
-        for extent in let_extent_stack.into_iter().rev() {
-            unpack!(block = this.pop_scope((extent, source_info), block));
+        for scope in let_scope_stack.into_iter().rev() {
+            unpack!(block = this.pop_scope((scope, source_info), block));
         }
         // Restore the original visibility scope.
         this.visibility_scope = outer_visibility_scope;
diff --git a/src/librustc_mir/build/cfg.rs b/src/librustc_mir/build/cfg.rs
index b390e2888f26c..d77fe5170e040 100644
--- a/src/librustc_mir/build/cfg.rs
+++ b/src/librustc_mir/build/cfg.rs
@@ -14,7 +14,7 @@
 //! Routines for manipulating the control-flow graph.
 
 use build::CFG;
-use rustc::middle::region::CodeExtent;
+use rustc::middle::region;
 use rustc::mir::*;
 
 impl<'tcx> CFG<'tcx> {
@@ -47,10 +47,10 @@ impl<'tcx> CFG<'tcx> {
     pub fn push_end_region(&mut self,
                            block: BasicBlock,
                            source_info: SourceInfo,
-                           extent: CodeExtent) {
+                           region_scope: region::Scope) {
         self.push(block, Statement {
             source_info,
-            kind: StatementKind::EndRegion(extent),
+            kind: StatementKind::EndRegion(region_scope),
         });
     }
 
diff --git a/src/librustc_mir/build/expr/as_constant.rs b/src/librustc_mir/build/expr/as_constant.rs
index 6d15f0a2e5d7f..a86b7f4d239a3 100644
--- a/src/librustc_mir/build/expr/as_constant.rs
+++ b/src/librustc_mir/build/expr/as_constant.rs
@@ -29,7 +29,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
         let Expr { ty, temp_lifetime: _, span, kind }
             = expr;
         match kind {
-            ExprKind::Scope { extent: _, value } =>
+            ExprKind::Scope { region_scope: _, value } =>
                 this.as_constant(value),
             ExprKind::Literal { literal } =>
                 Constant { span: span, ty: ty, literal: literal },
diff --git a/src/librustc_mir/build/expr/as_lvalue.rs b/src/librustc_mir/build/expr/as_lvalue.rs
index 04c23215463dd..9cbaff2c113b6 100644
--- a/src/librustc_mir/build/expr/as_lvalue.rs
+++ b/src/librustc_mir/build/expr/as_lvalue.rs
@@ -39,8 +39,10 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
         let expr_span = expr.span;
         let source_info = this.source_info(expr_span);
         match expr.kind {
-            ExprKind::Scope { extent, value } => {
-                this.in_scope((extent, source_info), block, |this| this.as_lvalue(block, value))
+            ExprKind::Scope { region_scope, value } => {
+                this.in_scope((region_scope, source_info), block, |this| {
+                    this.as_lvalue(block, value)
+                })
             }
             ExprKind::Field { lhs, name } => {
                 let lvalue = unpack!(block = this.as_lvalue(block, lhs));
@@ -56,10 +58,10 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                 let (usize_ty, bool_ty) = (this.hir.usize_ty(), this.hir.bool_ty());
 
                 let slice = unpack!(block = this.as_lvalue(block, lhs));
-                // extent=None so lvalue indexes live forever. They are scalars so they
+                // region_scope=None so lvalue indexes live forever. They are scalars so they
                 // do not need storage annotations, and they are often copied between
                 // places.
-                let idx = unpack!(block = this.as_operand(block, None, index));
+                let idx = unpack!(block = this.as_temp(block, None, index));
 
                 // bounds check:
                 let (len, lt) = (this.temp(usize_ty.clone(), expr_span),
@@ -68,12 +70,12 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                                      &len, Rvalue::Len(slice.clone()));
                 this.cfg.push_assign(block, source_info, // lt = idx < len
                                      &lt, Rvalue::BinaryOp(BinOp::Lt,
-                                                           idx.clone(),
+                                                           Operand::Consume(Lvalue::Local(idx)),
                                                            Operand::Consume(len.clone())));
 
                 let msg = AssertMessage::BoundsCheck {
                     len: Operand::Consume(len),
-                    index: idx.clone()
+                    index: Operand::Consume(Lvalue::Local(idx))
                 };
                 let success = this.assert(block, Operand::Consume(lt), true,
                                           msg, expr_span);
@@ -118,13 +120,15 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
             ExprKind::Return { .. } |
             ExprKind::Literal { .. } |
             ExprKind::InlineAsm { .. } |
+            ExprKind::Yield { .. } |
             ExprKind::Call { .. } => {
                 // these are not lvalues, so we need to make a temporary.
                 debug_assert!(match Category::of(&expr.kind) {
                     Some(Category::Lvalue) => false,
                     _ => true,
                 });
-                this.as_temp(block, expr.temp_lifetime, expr)
+                let temp = unpack!(block = this.as_temp(block, expr.temp_lifetime, expr));
+                block.and(Lvalue::Local(temp))
             }
         }
     }
diff --git a/src/librustc_mir/build/expr/as_operand.rs b/src/librustc_mir/build/expr/as_operand.rs
index 4679e0bb0a5c3..0a72ce8d05e14 100644
--- a/src/librustc_mir/build/expr/as_operand.rs
+++ b/src/librustc_mir/build/expr/as_operand.rs
@@ -13,7 +13,7 @@
 use build::{BlockAnd, BlockAndExtension, Builder};
 use build::expr::category::Category;
 use hair::*;
-use rustc::middle::region::CodeExtent;
+use rustc::middle::region;
 use rustc::mir::*;
 
 impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
@@ -39,7 +39,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
     /// The operand is known to be live until the end of `scope`.
     pub fn as_operand<M>(&mut self,
                          block: BasicBlock,
-                         scope: Option<CodeExtent>,
+                         scope: Option<region::Scope>,
                          expr: M) -> BlockAnd<Operand<'tcx>>
         where M: Mirror<'tcx, Output = Expr<'tcx>>
     {
@@ -49,16 +49,16 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
 
     fn expr_as_operand(&mut self,
                        mut block: BasicBlock,
-                       scope: Option<CodeExtent>,
+                       scope: Option<region::Scope>,
                        expr: Expr<'tcx>)
                        -> BlockAnd<Operand<'tcx>> {
         debug!("expr_as_operand(block={:?}, expr={:?})", block, expr);
         let this = self;
 
-        if let ExprKind::Scope { extent, value } = expr.kind {
+        if let ExprKind::Scope { region_scope, value } = expr.kind {
             let source_info = this.source_info(expr.span);
-            let extent = (extent, source_info);
-            return this.in_scope(extent, block, |this| {
+            let region_scope = (region_scope, source_info);
+            return this.in_scope(region_scope, block, |this| {
                 this.as_operand(block, scope, value)
             });
         }
@@ -74,7 +74,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
             Category::Rvalue(..) => {
                 let operand =
                     unpack!(block = this.as_temp(block, scope, expr));
-                block.and(Operand::Consume(operand))
+                block.and(Operand::Consume(Lvalue::Local(operand)))
             }
         }
     }
diff --git a/src/librustc_mir/build/expr/as_rvalue.rs b/src/librustc_mir/build/expr/as_rvalue.rs
index c74378bdadce5..c83283ee38e1f 100644
--- a/src/librustc_mir/build/expr/as_rvalue.rs
+++ b/src/librustc_mir/build/expr/as_rvalue.rs
@@ -21,7 +21,7 @@ use build::expr::category::{Category, RvalueFunc};
 use hair::*;
 use rustc_const_math::{ConstInt, ConstIsize};
 use rustc::middle::const_val::ConstVal;
-use rustc::middle::region::CodeExtent;
+use rustc::middle::region;
 use rustc::ty;
 use rustc::mir::*;
 use syntax::ast;
@@ -38,7 +38,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
     }
 
     /// Compile `expr`, yielding an rvalue.
-    pub fn as_rvalue<M>(&mut self, block: BasicBlock, scope: Option<CodeExtent>, expr: M)
+    pub fn as_rvalue<M>(&mut self, block: BasicBlock, scope: Option<region::Scope>, expr: M)
                         -> BlockAnd<Rvalue<'tcx>>
         where M: Mirror<'tcx, Output = Expr<'tcx>>
     {
@@ -48,7 +48,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
 
     fn expr_as_rvalue(&mut self,
                       mut block: BasicBlock,
-                      scope: Option<CodeExtent>,
+                      scope: Option<region::Scope>,
                       expr: Expr<'tcx>)
                       -> BlockAnd<Rvalue<'tcx>> {
         debug!("expr_as_rvalue(block={:?}, scope={:?}, expr={:?})", block, scope, expr);
@@ -58,9 +58,9 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
         let source_info = this.source_info(expr_span);
 
         match expr.kind {
-            ExprKind::Scope { extent, value } => {
-                let extent = (extent, source_info);
-                this.in_scope(extent, block, |this| this.as_rvalue(block, scope, value))
+            ExprKind::Scope { region_scope, value } => {
+                let region_scope = (region_scope, source_info);
+                this.in_scope(region_scope, block, |this| this.as_rvalue(block, scope, value))
             }
             ExprKind::Repeat { value, count } => {
                 let value_operand = unpack!(block = this.as_operand(block, scope, value));
@@ -96,23 +96,23 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
             }
             ExprKind::Box { value } => {
                 let value = this.hir.mirror(value);
-                let result = this.temp(expr.ty, expr_span);
+                let result = this.local_decls.push(LocalDecl::new_temp(expr.ty, expr_span));
+                this.cfg.push(block, Statement {
+                    source_info,
+                    kind: StatementKind::StorageLive(result)
+                });
                 if let Some(scope) = scope {
                     // schedule a shallow free of that memory, lest we unwind:
-                    this.cfg.push(block, Statement {
-                        source_info,
-                        kind: StatementKind::StorageLive(result.clone())
-                    });
-                    this.schedule_drop(expr_span, scope, &result, value.ty);
+                    this.schedule_drop(expr_span, scope, &Lvalue::Local(result), value.ty);
                 }
 
                 // malloc some memory of suitable type (thus far, uninitialized):
                 let box_ = Rvalue::NullaryOp(NullOp::Box, value.ty);
-                this.cfg.push_assign(block, source_info, &result, box_);
+                this.cfg.push_assign(block, source_info, &Lvalue::Local(result), box_);
 
                 // initialize the box contents:
-                unpack!(block = this.into(&result.clone().deref(), block, value));
-                block.and(Rvalue::Use(Operand::Consume(result)))
+                unpack!(block = this.into(&Lvalue::Local(result).deref(), block, value));
+                block.and(Rvalue::Use(Operand::Consume(Lvalue::Local(result))))
             }
             ExprKind::Cast { source } => {
                 let source = this.hir.mirror(source);
@@ -185,12 +185,26 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
 
                 block.and(Rvalue::Aggregate(box AggregateKind::Tuple, fields))
             }
-            ExprKind::Closure { closure_id, substs, upvars } => { // see (*) above
-                let upvars =
+            ExprKind::Closure { closure_id, substs, upvars, interior } => { // see (*) above
+                let mut operands: Vec<_> =
                     upvars.into_iter()
                           .map(|upvar| unpack!(block = this.as_operand(block, scope, upvar)))
                           .collect();
-                block.and(Rvalue::Aggregate(box AggregateKind::Closure(closure_id, substs), upvars))
+                let result = if let Some(interior) = interior {
+                    // Add the state operand since it follows the upvars in the generator
+                    // struct. See librustc_mir/transform/generator.rs for more details.
+                    operands.push(Operand::Constant(box Constant {
+                        span: expr_span,
+                        ty: this.hir.tcx().types.u32,
+                        literal: Literal::Value {
+                            value: ConstVal::Integral(ConstInt::U32(0)),
+                        },
+                    }));
+                    box AggregateKind::Generator(closure_id, substs, interior)
+                } else {
+                    box AggregateKind::Closure(closure_id, substs)
+                };
+                block.and(Rvalue::Aggregate(result, operands))
             }
             ExprKind::Adt {
                 adt_def, variant_index, substs, fields, base
@@ -232,6 +246,17 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                 block = unpack!(this.stmt_expr(block, expr));
                 block.and(this.unit_rvalue())
             }
+            ExprKind::Yield { value } => {
+                let value = unpack!(block = this.as_operand(block, scope, value));
+                let resume = this.cfg.start_new_block();
+                let cleanup = this.generator_drop_cleanup();
+                this.cfg.terminate(block, source_info, TerminatorKind::Yield {
+                    value: value,
+                    resume: resume,
+                    drop: cleanup,
+                });
+                resume.and(this.unit_rvalue())
+            }
             ExprKind::Literal { .. } |
             ExprKind::Block { .. } |
             ExprKind::Match { .. } |
diff --git a/src/librustc_mir/build/expr/as_temp.rs b/src/librustc_mir/build/expr/as_temp.rs
index 4f248ddb0e2cf..7826769600bfa 100644
--- a/src/librustc_mir/build/expr/as_temp.rs
+++ b/src/librustc_mir/build/expr/as_temp.rs
@@ -13,7 +13,7 @@
 use build::{BlockAnd, BlockAndExtension, Builder};
 use build::expr::category::Category;
 use hair::*;
-use rustc::middle::region::CodeExtent;
+use rustc::middle::region;
 use rustc::mir::*;
 
 impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
@@ -21,9 +21,9 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
     /// up rvalues so as to freeze the value that will be consumed.
     pub fn as_temp<M>(&mut self,
                       block: BasicBlock,
-                      temp_lifetime: Option<CodeExtent>,
+                      temp_lifetime: Option<region::Scope>,
                       expr: M)
-                      -> BlockAnd<Lvalue<'tcx>>
+                      -> BlockAnd<Local>
         where M: Mirror<'tcx, Output = Expr<'tcx>>
     {
         let expr = self.hir.mirror(expr);
@@ -32,28 +32,28 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
 
     fn expr_as_temp(&mut self,
                     mut block: BasicBlock,
-                    temp_lifetime: Option<CodeExtent>,
+                    temp_lifetime: Option<region::Scope>,
                     expr: Expr<'tcx>)
-                    -> BlockAnd<Lvalue<'tcx>> {
+                    -> BlockAnd<Local> {
         debug!("expr_as_temp(block={:?}, temp_lifetime={:?}, expr={:?})",
                block, temp_lifetime, expr);
         let this = self;
 
         let expr_span = expr.span;
         let source_info = this.source_info(expr_span);
-        if let ExprKind::Scope { extent, value } = expr.kind {
-            return this.in_scope((extent, source_info), block, |this| {
+        if let ExprKind::Scope { region_scope, value } = expr.kind {
+            return this.in_scope((region_scope, source_info), block, |this| {
                 this.as_temp(block, temp_lifetime, value)
             });
         }
 
-        let expr_ty = expr.ty.clone();
-        let temp = this.temp(expr_ty.clone(), expr_span);
+        let expr_ty = expr.ty;
+        let temp = this.local_decls.push(LocalDecl::new_temp(expr_ty, expr_span));
 
-        if !expr_ty.is_never() && temp_lifetime.is_some() {
+        if !expr_ty.is_never() {
             this.cfg.push(block, Statement {
                 source_info,
-                kind: StatementKind::StorageLive(temp.clone())
+                kind: StatementKind::StorageLive(temp)
             });
         }
 
@@ -68,10 +68,10 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
             Category::Lvalue => {
                 let lvalue = unpack!(block = this.as_lvalue(block, expr));
                 let rvalue = Rvalue::Use(Operand::Consume(lvalue));
-                this.cfg.push_assign(block, source_info, &temp, rvalue);
+                this.cfg.push_assign(block, source_info, &Lvalue::Local(temp), rvalue);
             }
             _ => {
-                unpack!(block = this.into(&temp, block, expr));
+                unpack!(block = this.into(&Lvalue::Local(temp), block, expr));
             }
         }
 
@@ -79,7 +79,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
         // anything because no values with a destructor can be created in
         // a constant at this time, even if the type may need dropping.
         if let Some(temp_lifetime) = temp_lifetime {
-            this.schedule_drop(expr_span, temp_lifetime, &temp, expr_ty);
+            this.schedule_drop(expr_span, temp_lifetime, &Lvalue::Local(temp), expr_ty);
         }
 
         block.and(temp)
diff --git a/src/librustc_mir/build/expr/category.rs b/src/librustc_mir/build/expr/category.rs
index 35173bb598c7c..f05411aacab19 100644
--- a/src/librustc_mir/build/expr/category.rs
+++ b/src/librustc_mir/build/expr/category.rs
@@ -77,6 +77,7 @@ impl Category {
             ExprKind::Borrow { .. } |
             ExprKind::Assign { .. } |
             ExprKind::AssignOp { .. } |
+            ExprKind::Yield { .. } |
             ExprKind::InlineAsm { .. } =>
                 Some(Category::Rvalue(RvalueFunc::AsRvalue)),
 
diff --git a/src/librustc_mir/build/expr/into.rs b/src/librustc_mir/build/expr/into.rs
index 576b1059e5997..80a126dc42569 100644
--- a/src/librustc_mir/build/expr/into.rs
+++ b/src/librustc_mir/build/expr/into.rs
@@ -38,9 +38,9 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
         let source_info = this.source_info(expr_span);
 
         match expr.kind {
-            ExprKind::Scope { extent, value } => {
-                let extent = (extent, source_info);
-                this.in_scope(extent, block, |this| this.into(destination, block, value))
+            ExprKind::Scope { region_scope, value } => {
+                let region_scope = (region_scope, source_info);
+                this.in_scope(region_scope, block, |this| this.into(destination, block, value))
             }
             ExprKind::Block { body: ast_block } => {
                 this.ast_block(destination, block, ast_block, source_info)
@@ -229,7 +229,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
 
                     let topmost_scope = this.topmost_scope();
                     let ptr = unpack!(block = this.as_temp(block, Some(topmost_scope), ptr));
-                    this.into(&ptr.deref(), block, val)
+                    this.into(&Lvalue::Local(ptr).deref(), block, val)
                 } else {
                     let args: Vec<_> =
                         args.into_iter()
@@ -284,6 +284,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
             ExprKind::Index { .. } |
             ExprKind::Deref { .. } |
             ExprKind::Literal { .. } |
+            ExprKind::Yield { .. } |
             ExprKind::Field { .. } => {
                 debug_assert!(match Category::of(&expr.kind).unwrap() {
                     Category::Rvalue(RvalueFunc::Into) => false,
diff --git a/src/librustc_mir/build/expr/stmt.rs b/src/librustc_mir/build/expr/stmt.rs
index 0da722f72a15a..84468d5d6dc18 100644
--- a/src/librustc_mir/build/expr/stmt.rs
+++ b/src/librustc_mir/build/expr/stmt.rs
@@ -22,9 +22,11 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
         // Handle a number of expressions that don't need a destination at all. This
         // avoids needing a mountain of temporary `()` variables.
         match expr.kind {
-            ExprKind::Scope { extent, value } => {
+            ExprKind::Scope { region_scope, value } => {
                 let value = this.hir.mirror(value);
-                this.in_scope((extent, source_info), block, |this| this.stmt_expr(block, value))
+                this.in_scope((region_scope, source_info), block, |this| {
+                    this.stmt_expr(block, value)
+                })
             }
             ExprKind::Assign { lhs, rhs } => {
                 let lhs = this.hir.mirror(lhs);
@@ -77,29 +79,29 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                 block.unit()
             }
             ExprKind::Continue { label } => {
-                let BreakableScope { continue_block, extent, .. } =
+                let BreakableScope { continue_block, region_scope, .. } =
                     *this.find_breakable_scope(expr_span, label);
                 let continue_block = continue_block.expect(
                     "Attempted to continue in non-continuable breakable block");
-                this.exit_scope(expr_span, (extent, source_info), block, continue_block);
+                this.exit_scope(expr_span, (region_scope, source_info), block, continue_block);
                 this.cfg.start_new_block().unit()
             }
             ExprKind::Break { label, value } => {
-                let (break_block, extent, destination) = {
+                let (break_block, region_scope, destination) = {
                     let BreakableScope {
                         break_block,
-                        extent,
+                        region_scope,
                         ref break_destination,
                         ..
                     } = *this.find_breakable_scope(expr_span, label);
-                    (break_block, extent, break_destination.clone())
+                    (break_block, region_scope, break_destination.clone())
                 };
                 if let Some(value) = value {
                     unpack!(block = this.into(&destination, block, value))
                 } else {
                     this.cfg.push_assign_unit(block, source_info, &destination)
                 }
-                this.exit_scope(expr_span, (extent, source_info), block, break_block);
+                this.exit_scope(expr_span, (region_scope, source_info), block, break_block);
                 this.cfg.start_new_block().unit()
             }
             ExprKind::Return { value } => {
@@ -114,9 +116,9 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                         block
                     }
                 };
-                let extent = this.extent_of_return_scope();
+                let region_scope = this.region_scope_of_return_scope();
                 let return_block = this.return_block();
-                this.exit_scope(expr_span, (extent, source_info), block, return_block);
+                this.exit_scope(expr_span, (region_scope, source_info), block, return_block);
                 this.cfg.start_new_block().unit()
             }
             ExprKind::InlineAsm { asm, outputs, inputs } => {
diff --git a/src/librustc_mir/build/matches/mod.rs b/src/librustc_mir/build/matches/mod.rs
index 78805ba87ec22..ec2e487b4e74c 100644
--- a/src/librustc_mir/build/matches/mod.rs
+++ b/src/librustc_mir/build/matches/mod.rs
@@ -194,7 +194,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
         let source_info = self.source_info(span);
         self.cfg.push(block, Statement {
             source_info,
-            kind: StatementKind::StorageLive(Lvalue::Local(local_id))
+            kind: StatementKind::StorageLive(local_id)
         });
         Lvalue::Local(local_id)
     }
@@ -202,8 +202,9 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
     pub fn schedule_drop_for_binding(&mut self, var: NodeId, span: Span) {
         let local_id = self.var_indices[&var];
         let var_ty = self.local_decls[local_id].ty;
-        let extent = self.hir.region_maps.var_scope(var);
-        self.schedule_drop(span, extent, &Lvalue::Local(local_id), var_ty);
+        let hir_id = self.hir.tcx().hir.node_to_hir_id(var);
+        let region_scope = self.hir.region_scope_tree.var_scope(hir_id.local_id);
+        self.schedule_drop(span, region_scope, &Lvalue::Local(local_id), var_ty);
     }
 
     pub fn visit_bindings<F>(&mut self, pattern: &Pattern<'tcx>, f: &mut F)
@@ -712,6 +713,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
             ty: var_ty.clone(),
             name: Some(name),
             source_info,
+            internal: false,
             is_user_variable: true,
         });
         self.var_indices.insert(var_id, var);
diff --git a/src/librustc_mir/build/mod.rs b/src/librustc_mir/build/mod.rs
index d7a295a1c3a24..7d1aace873e82 100644
--- a/src/librustc_mir/build/mod.rs
+++ b/src/librustc_mir/build/mod.rs
@@ -14,7 +14,7 @@ use hair::cx::Cx;
 use hair::Pattern;
 use rustc::hir;
 use rustc::hir::def_id::DefId;
-use rustc::middle::region::CodeExtent;
+use rustc::middle::region;
 use rustc::mir::*;
 use rustc::mir::transform::MirSource;
 use rustc::mir::visit::{MutVisitor, Lookup};
@@ -71,7 +71,7 @@ pub fn mir_build<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) -> Mir<'t
             // Assume that everything other than closures
             // is a constant "initializer" expression.
             match expr.node {
-                hir::ExprClosure(_, _, body, _) => body,
+                hir::ExprClosure(_, _, body, _, _) => body,
                 _ => hir::BodyId { node_id: expr.id }
             }
         }
@@ -95,13 +95,18 @@ pub fn mir_build<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) -> Mir<'t
 
             let ty = tcx.type_of(tcx.hir.local_def_id(id));
             let mut abi = fn_sig.abi;
-            let implicit_argument = if let ty::TyClosure(..) = ty.sty {
-                // HACK(eddyb) Avoid having RustCall on closures,
-                // as it adds unnecessary (and wrong) auto-tupling.
-                abi = Abi::Rust;
-                Some((closure_self_ty(tcx, id, body_id), None))
-            } else {
-                None
+            let implicit_argument = match ty.sty {
+                ty::TyClosure(..) => {
+                    // HACK(eddyb) Avoid having RustCall on closures,
+                    // as it adds unnecessary (and wrong) auto-tupling.
+                    abi = Abi::Rust;
+                    Some((closure_self_ty(tcx, id, body_id), None))
+                }
+                ty::TyGenerator(..) => {
+                    let gen_ty =  tcx.body_tables(body_id).node_id_to_type(fn_hir_id);
+                    Some((gen_ty, None))
+                }
+                _ => None,
             };
 
             let body = tcx.hir.body(body_id);
@@ -114,7 +119,15 @@ pub fn mir_build<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) -> Mir<'t
                     });
 
             let arguments = implicit_argument.into_iter().chain(explicit_arguments);
-            build::construct_fn(cx, id, arguments, abi, fn_sig.output(), body)
+
+            let (yield_ty, return_ty) = if body.is_generator {
+                let gen_sig = cx.tables().generator_sigs()[fn_hir_id].clone().unwrap();
+                (Some(gen_sig.yield_ty), gen_sig.return_ty)
+            } else {
+                (None, fn_sig.output())
+            };
+
+            build::construct_fn(cx, id, arguments, abi, return_ty, yield_ty, body)
         } else {
             build::construct_const(cx, body_id)
         };
@@ -199,7 +212,7 @@ fn create_constructor_shim<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 ///////////////////////////////////////////////////////////////////////////
 // BuildMir -- walks a crate, looking for fn items and methods to build MIR from
 
-fn closure_self_ty<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
+pub fn closure_self_ty<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                              closure_expr_id: ast::NodeId,
                              body_id: hir::BodyId)
                              -> Ty<'tcx> {
@@ -328,6 +341,7 @@ fn construct_fn<'a, 'gcx, 'tcx, A>(hir: Cx<'a, 'gcx, 'tcx>,
                                    arguments: A,
                                    abi: Abi,
                                    return_ty: Ty<'gcx>,
+                                   yield_ty: Option<Ty<'gcx>>,
                                    body: &'gcx hir::Body)
                                    -> Mir<'tcx>
     where A: Iterator<Item=(Ty<'gcx>, Option<&'gcx hir::Pat>)>
@@ -336,18 +350,21 @@ fn construct_fn<'a, 'gcx, 'tcx, A>(hir: Cx<'a, 'gcx, 'tcx>,
 
     let tcx = hir.tcx();
     let span = tcx.hir.span(fn_id);
-    let mut builder = Builder::new(hir.clone(), span, arguments.len(), return_ty);
+    let mut builder = Builder::new(hir.clone(),
+        span,
+        arguments.len(),
+        return_ty);
 
-    let call_site_extent = CodeExtent::CallSiteScope(body.id());
-    let arg_extent = CodeExtent::ParameterScope(body.id());
+    let call_site_scope = region::Scope::CallSite(body.value.hir_id.local_id);
+    let arg_scope = region::Scope::Arguments(body.value.hir_id.local_id);
     let mut block = START_BLOCK;
     let source_info = builder.source_info(span);
-    unpack!(block = builder.in_scope((call_site_extent, source_info), block, |builder| {
-        unpack!(block = builder.in_scope((arg_extent, source_info), block, |builder| {
-            builder.args_and_body(block, &arguments, arg_extent, &body.value)
+    unpack!(block = builder.in_scope((call_site_scope, source_info), block, |builder| {
+        unpack!(block = builder.in_scope((arg_scope, source_info), block, |builder| {
+            builder.args_and_body(block, &arguments, arg_scope, &body.value)
         }));
         // Attribute epilogue to function's closing brace
-        let fn_end = Span { lo: span.hi, ..span };
+        let fn_end = span.with_lo(span.hi());
         let source_info = builder.source_info(fn_end);
         let return_block = builder.return_block();
         builder.cfg.terminate(block, source_info,
@@ -391,7 +408,7 @@ fn construct_fn<'a, 'gcx, 'tcx, A>(hir: Cx<'a, 'gcx, 'tcx>,
         }).collect()
     });
 
-    let mut mir = builder.finish(upvar_decls, return_ty);
+    let mut mir = builder.finish(upvar_decls, return_ty, yield_ty);
     mir.spread_arg = spread_arg;
     mir
 }
@@ -416,7 +433,7 @@ fn construct_const<'a, 'gcx, 'tcx>(hir: Cx<'a, 'gcx, 'tcx>,
     // Constants can't `return` so a return block should not be created.
     assert_eq!(builder.cached_return_block, None);
 
-    builder.finish(vec![], ty)
+    builder.finish(vec![], ty, None)
 }
 
 fn construct_error<'a, 'gcx, 'tcx>(hir: Cx<'a, 'gcx, 'tcx>,
@@ -427,7 +444,7 @@ fn construct_error<'a, 'gcx, 'tcx>(hir: Cx<'a, 'gcx, 'tcx>,
     let mut builder = Builder::new(hir, span, 0, ty);
     let source_info = builder.source_info(span);
     builder.cfg.terminate(START_BLOCK, source_info, TerminatorKind::Unreachable);
-    builder.finish(vec![], ty)
+    builder.finish(vec![], ty, None)
 }
 
 impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
@@ -462,7 +479,8 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
 
     fn finish(self,
               upvar_decls: Vec<UpvarDecl>,
-              return_ty: Ty<'tcx>)
+              return_ty: Ty<'tcx>,
+              yield_ty: Option<Ty<'tcx>>)
               -> Mir<'tcx> {
         for (index, block) in self.cfg.basic_blocks.iter().enumerate() {
             if block.terminator.is_none() {
@@ -474,6 +492,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                  self.visibility_scopes,
                  IndexVec::new(),
                  return_ty,
+                 yield_ty,
                  self.local_decls,
                  self.arg_count,
                  upvar_decls,
@@ -484,7 +503,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
     fn args_and_body(&mut self,
                      mut block: BasicBlock,
                      arguments: &[(Ty<'gcx>, Option<&'gcx hir::Pat>)],
-                     argument_extent: CodeExtent,
+                     argument_scope: region::Scope,
                      ast_body: &'gcx hir::Expr)
                      -> BlockAnd<()>
     {
@@ -506,6 +525,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                     span: pattern.map_or(self.fn_span, |pat| pat.span)
                 },
                 name,
+                internal: false,
                 is_user_variable: false,
             });
         }
@@ -527,7 +547,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
 
             // Make sure we drop (parts of) the argument even when not matched on.
             self.schedule_drop(pattern.as_ref().map_or(ast_body.span, |pat| pat.span),
-                               argument_extent, &lvalue, ty);
+                               argument_scope, &lvalue, ty);
 
         }
 
diff --git a/src/librustc_mir/build/scope.rs b/src/librustc_mir/build/scope.rs
index c36da9410f34a..ed598c876f3e9 100644
--- a/src/librustc_mir/build/scope.rs
+++ b/src/librustc_mir/build/scope.rs
@@ -12,7 +12,7 @@
 Managing the scope stack. The scopes are tied to lexical scopes, so as
 we descend the HAIR, we push a scope on the stack, translate ite
 contents, and then pop it off. Every scope is named by a
-`CodeExtent`.
+`region::Scope`.
 
 ### SEME Regions
 
@@ -23,7 +23,7 @@ via a `break` or `return` or just by fallthrough, that marks an exit
 from the scope. Each lexical scope thus corresponds to a single-entry,
 multiple-exit (SEME) region in the control-flow graph.
 
-For now, we keep a mapping from each `CodeExtent` to its
+For now, we keep a mapping from each `region::Scope` to its
 corresponding SEME region for later reference (see caveat in next
 paragraph). This is because region scopes are tied to
 them. Eventually, when we shift to non-lexical lifetimes, there should
@@ -88,7 +88,7 @@ should go to.
 */
 
 use build::{BlockAnd, BlockAndExtension, Builder, CFG};
-use rustc::middle::region::CodeExtent;
+use rustc::middle::region;
 use rustc::ty::Ty;
 use rustc::mir::*;
 use rustc::mir::transform::MirSource;
@@ -101,11 +101,11 @@ pub struct Scope<'tcx> {
     /// The visibility scope this scope was created in.
     visibility_scope: VisibilityScope,
 
-    /// the extent of this scope within source code.
-    extent: CodeExtent,
+    /// the region span of this scope within source code.
+    region_scope: region::Scope,
 
-    /// the span of that extent
-    extent_span: Span,
+    /// the span of that region_scope
+    region_scope_span: Span,
 
     /// Whether there's anything to do for the cleanup path, that is,
     /// when unwinding through this scope. This includes destructors,
@@ -125,7 +125,10 @@ pub struct Scope<'tcx> {
     drops: Vec<DropData<'tcx>>,
 
     /// The cache for drop chain on “normal” exit into a particular BasicBlock.
-    cached_exits: FxHashMap<(BasicBlock, CodeExtent), BasicBlock>,
+    cached_exits: FxHashMap<(BasicBlock, region::Scope), BasicBlock>,
+
+    /// The cache for drop chain on "generator drop" exit.
+    cached_generator_drop: Option<BasicBlock>,
 }
 
 #[derive(Debug)]
@@ -140,22 +143,30 @@ struct DropData<'tcx> {
     kind: DropKind
 }
 
+#[derive(Debug, Default, Clone, Copy)]
+struct CachedBlock {
+    /// The cached block for the cleanups-on-diverge path. This block
+    /// contains code to run the current drop and all the preceding
+    /// drops (i.e. those having lower index in Drop’s Scope drop
+    /// array)
+    unwind: Option<BasicBlock>,
+
+    /// The cached block for unwinds during cleanups-on-generator-drop path
+    generator_drop: Option<BasicBlock>,
+}
+
 #[derive(Debug)]
 enum DropKind {
     Value {
-        /// The cached block for the cleanups-on-diverge path. This block
-        /// contains code to run the current drop and all the preceding
-        /// drops (i.e. those having lower index in Drop’s Scope drop
-        /// array)
-        cached_block: Option<BasicBlock>
+        cached_block: CachedBlock,
     },
     Storage
 }
 
 #[derive(Clone, Debug)]
 pub struct BreakableScope<'tcx> {
-    /// Extent of the loop
-    pub extent: CodeExtent,
+    /// Region scope of the loop
+    pub region_scope: region::Scope,
     /// Where the body of the loop begins. `None` if block
     pub continue_block: Option<BasicBlock>,
     /// Block to branch into when the loop or block terminates (either by being `break`-en out
@@ -166,6 +177,29 @@ pub struct BreakableScope<'tcx> {
     pub break_destination: Lvalue<'tcx>,
 }
 
+impl CachedBlock {
+    fn invalidate(&mut self) {
+        self.generator_drop = None;
+        self.unwind = None;
+    }
+
+    fn get(&self, generator_drop: bool) -> Option<BasicBlock> {
+        if generator_drop {
+            self.generator_drop
+        } else {
+            self.unwind
+        }
+    }
+
+    fn ref_mut(&mut self, generator_drop: bool) -> &mut Option<BasicBlock> {
+        if generator_drop {
+            &mut self.generator_drop
+        } else {
+            &mut self.unwind
+        }
+    }
+}
+
 impl DropKind {
     fn may_panic(&self) -> bool {
         match *self {
@@ -187,7 +221,7 @@ impl<'tcx> Scope<'tcx> {
         if !unwind { return; }
         for dropdata in &mut self.drops {
             if let DropKind::Value { ref mut cached_block } = dropdata.kind {
-                *cached_block = None;
+                cached_block.invalidate();
             }
         }
     }
@@ -196,10 +230,12 @@ impl<'tcx> Scope<'tcx> {
     ///
     /// Precondition: the caches must be fully filled (i.e. diverge_cleanup is called) in order for
     /// this method to work correctly.
-    fn cached_block(&self) -> Option<BasicBlock> {
+    fn cached_block(&self, generator_drop: bool) -> Option<BasicBlock> {
         let mut drops = self.drops.iter().rev().filter_map(|data| {
             match data.kind {
-                DropKind::Value { cached_block } => Some(cached_block),
+                DropKind::Value { cached_block } => {
+                    Some(cached_block.get(generator_drop))
+                }
                 DropKind::Storage => None
             }
         });
@@ -233,9 +269,9 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                                     f: F) -> R
         where F: FnOnce(&mut Builder<'a, 'gcx, 'tcx>) -> R
     {
-        let extent = self.topmost_scope();
+        let region_scope = self.topmost_scope();
         let scope = BreakableScope {
-            extent,
+            region_scope,
             continue_block: loop_block,
             break_block,
             break_destination,
@@ -243,41 +279,41 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
         self.breakable_scopes.push(scope);
         let res = f(self);
         let breakable_scope = self.breakable_scopes.pop().unwrap();
-        assert!(breakable_scope.extent == extent);
+        assert!(breakable_scope.region_scope == region_scope);
         res
     }
 
     pub fn in_opt_scope<F, R>(&mut self,
-                              opt_extent: Option<(CodeExtent, SourceInfo)>,
+                              opt_scope: Option<(region::Scope, SourceInfo)>,
                               mut block: BasicBlock,
                               f: F)
                               -> BlockAnd<R>
         where F: FnOnce(&mut Builder<'a, 'gcx, 'tcx>) -> BlockAnd<R>
     {
-        debug!("in_opt_scope(opt_extent={:?}, block={:?})", opt_extent, block);
-        if let Some(extent) = opt_extent { self.push_scope(extent); }
+        debug!("in_opt_scope(opt_scope={:?}, block={:?})", opt_scope, block);
+        if let Some(region_scope) = opt_scope { self.push_scope(region_scope); }
         let rv = unpack!(block = f(self));
-        if let Some(extent) = opt_extent {
-            unpack!(block = self.pop_scope(extent, block));
+        if let Some(region_scope) = opt_scope {
+            unpack!(block = self.pop_scope(region_scope, block));
         }
-        debug!("in_scope: exiting opt_extent={:?} block={:?}", opt_extent, block);
+        debug!("in_scope: exiting opt_scope={:?} block={:?}", opt_scope, block);
         block.and(rv)
     }
 
     /// Convenience wrapper that pushes a scope and then executes `f`
     /// to build its contents, popping the scope afterwards.
     pub fn in_scope<F, R>(&mut self,
-                          extent: (CodeExtent, SourceInfo),
+                          region_scope: (region::Scope, SourceInfo),
                           mut block: BasicBlock,
                           f: F)
                           -> BlockAnd<R>
         where F: FnOnce(&mut Builder<'a, 'gcx, 'tcx>) -> BlockAnd<R>
     {
-        debug!("in_scope(extent={:?}, block={:?})", extent, block);
-        self.push_scope(extent);
+        debug!("in_scope(region_scope={:?}, block={:?})", region_scope, block);
+        self.push_scope(region_scope);
         let rv = unpack!(block = f(self));
-        unpack!(block = self.pop_scope(extent, block));
-        debug!("in_scope: exiting extent={:?} block={:?}", extent, block);
+        unpack!(block = self.pop_scope(region_scope, block));
+        debug!("in_scope: exiting region_scope={:?} block={:?}", region_scope, block);
         block.and(rv)
     }
 
@@ -285,27 +321,28 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
     /// scope and call `pop_scope` afterwards. Note that these two
     /// calls must be paired; using `in_scope` as a convenience
     /// wrapper maybe preferable.
-    pub fn push_scope(&mut self, extent: (CodeExtent, SourceInfo)) {
-        debug!("push_scope({:?})", extent);
+    pub fn push_scope(&mut self, region_scope: (region::Scope, SourceInfo)) {
+        debug!("push_scope({:?})", region_scope);
         let vis_scope = self.visibility_scope;
         self.scopes.push(Scope {
             visibility_scope: vis_scope,
-            extent: extent.0,
-            extent_span: extent.1.span,
+            region_scope: region_scope.0,
+            region_scope_span: region_scope.1.span,
             needs_cleanup: false,
             drops: vec![],
+            cached_generator_drop: None,
             cached_exits: FxHashMap()
         });
     }
 
-    /// Pops a scope, which should have extent `extent`, adding any
-    /// drops onto the end of `block` that are needed.  This must
-    /// match 1-to-1 with `push_scope`.
+    /// Pops a scope, which should have region scope `region_scope`,
+    /// adding any drops onto the end of `block` that are needed.
+    /// This must match 1-to-1 with `push_scope`.
     pub fn pop_scope(&mut self,
-                     extent: (CodeExtent, SourceInfo),
+                     region_scope: (region::Scope, SourceInfo),
                      mut block: BasicBlock)
                      -> BlockAnd<()> {
-        debug!("pop_scope({:?}, {:?})", extent, block);
+        debug!("pop_scope({:?}, {:?})", region_scope, block);
         // If we are emitting a `drop` statement, we need to have the cached
         // diverge cleanup pads ready in case that drop panics.
         let may_panic =
@@ -314,32 +351,35 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
             self.diverge_cleanup();
         }
         let scope = self.scopes.pop().unwrap();
-        assert_eq!(scope.extent, extent.0);
+        assert_eq!(scope.region_scope, region_scope.0);
         unpack!(block = build_scope_drops(&mut self.cfg,
                                           &scope,
                                           &self.scopes,
                                           block,
-                                          self.arg_count));
+                                          self.arg_count,
+                                          false));
 
-        self.cfg.push_end_region(block, extent.1, scope.extent);
+        self.cfg.push_end_region(block, region_scope.1, scope.region_scope);
         block.unit()
     }
 
 
     /// Branch out of `block` to `target`, exiting all scopes up to
-    /// and including `extent`.  This will insert whatever drops are
+    /// and including `region_scope`.  This will insert whatever drops are
     /// needed, as well as tracking this exit for the SEME region. See
     /// module comment for details.
     pub fn exit_scope(&mut self,
                       span: Span,
-                      extent: (CodeExtent, SourceInfo),
+                      region_scope: (region::Scope, SourceInfo),
                       mut block: BasicBlock,
                       target: BasicBlock) {
-        debug!("exit_scope(extent={:?}, block={:?}, target={:?})", extent, block, target);
-        let scope_count = 1 + self.scopes.iter().rev().position(|scope| scope.extent == extent.0)
-                                                      .unwrap_or_else(||{
-            span_bug!(span, "extent {:?} does not enclose", extent)
-        });
+        debug!("exit_scope(region_scope={:?}, block={:?}, target={:?})",
+               region_scope, block, target);
+        let scope_count = 1 + self.scopes.iter().rev()
+            .position(|scope| scope.region_scope == region_scope.0)
+            .unwrap_or_else(|| {
+                span_bug!(span, "region_scope {:?} does not enclose", region_scope)
+            });
         let len = self.scopes.len();
         assert!(scope_count < len, "should not use `exit_scope` to pop ALL scopes");
 
@@ -355,7 +395,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
         let mut rest = &mut self.scopes[(len - scope_count)..];
         while let Some((scope, rest_)) = {rest}.split_last_mut() {
             rest = rest_;
-            block = if let Some(&e) = scope.cached_exits.get(&(target, extent.0)) {
+            block = if let Some(&e) = scope.cached_exits.get(&(target, region_scope.0)) {
                 self.cfg.terminate(block, scope.source_info(span),
                                    TerminatorKind::Goto { target: e });
                 return;
@@ -363,17 +403,18 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                 let b = self.cfg.start_new_block();
                 self.cfg.terminate(block, scope.source_info(span),
                                    TerminatorKind::Goto { target: b });
-                scope.cached_exits.insert((target, extent.0), b);
+                scope.cached_exits.insert((target, region_scope.0), b);
                 b
             };
             unpack!(block = build_scope_drops(&mut self.cfg,
                                               scope,
                                               rest,
                                               block,
-                                              self.arg_count));
+                                              self.arg_count,
+                                              false));
 
             // End all regions for scopes out of which we are breaking.
-            self.cfg.push_end_region(block, extent.1, scope.extent);
+            self.cfg.push_end_region(block, region_scope.1, scope.region_scope);
         }
         }
         let scope = &self.scopes[len - scope_count];
@@ -381,6 +422,55 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                            TerminatorKind::Goto { target: target });
     }
 
+    /// Creates a path that performs all required cleanup for dropping a generator.
+    ///
+    /// This path terminates in GeneratorDrop. Returns the start of the path.
+    /// None indicates there’s no cleanup to do at this point.
+    pub fn generator_drop_cleanup(&mut self) -> Option<BasicBlock> {
+        if !self.scopes.iter().any(|scope| scope.needs_cleanup) {
+            return None;
+        }
+
+        // Fill in the cache
+        self.diverge_cleanup_gen(true);
+
+        let src_info = self.scopes[0].source_info(self.fn_span);
+        let mut block = self.cfg.start_new_block();
+        let result = block;
+        let mut rest = &mut self.scopes[..];
+
+        while let Some((scope, rest_)) = {rest}.split_last_mut() {
+            rest = rest_;
+            if !scope.needs_cleanup {
+                continue;
+            }
+            block = if let Some(b) = scope.cached_generator_drop {
+                self.cfg.terminate(block, src_info,
+                                   TerminatorKind::Goto { target: b });
+                return Some(result);
+            } else {
+                let b = self.cfg.start_new_block();
+                scope.cached_generator_drop = Some(b);
+                self.cfg.terminate(block, src_info,
+                                   TerminatorKind::Goto { target: b });
+                b
+            };
+            unpack!(block = build_scope_drops(&mut self.cfg,
+                                              scope,
+                                              rest,
+                                              block,
+                                              self.arg_count,
+                                              true));
+
+            // End all regions for scopes out of which we are breaking.
+            self.cfg.push_end_region(block, src_info, scope.region_scope);
+        }
+
+        self.cfg.terminate(block, src_info, TerminatorKind::GeneratorDrop);
+
+        Some(result)
+    }
+
     /// Creates a new visibility scope, nested in the current one.
     pub fn new_visibility_scope(&mut self, span: Span) -> VisibilityScope {
         let parent = self.visibility_scope;
@@ -398,12 +488,12 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
     /// resolving `break` and `continue`.
     pub fn find_breakable_scope(&mut self,
                            span: Span,
-                           label: CodeExtent)
+                           label: region::Scope)
                            -> &mut BreakableScope<'tcx> {
         // find the loop-scope with the correct id
         self.breakable_scopes.iter_mut()
             .rev()
-            .filter(|breakable_scope| breakable_scope.extent == label)
+            .filter(|breakable_scope| breakable_scope.region_scope == label)
             .next()
             .unwrap_or_else(|| span_bug!(span, "no enclosing breakable scope found"))
     }
@@ -416,23 +506,23 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
         }
     }
 
-    /// Returns the extent of the scope which should be exited by a
+    /// Returns the `region::Scope` of the scope which should be exited by a
     /// return.
-    pub fn extent_of_return_scope(&self) -> CodeExtent {
+    pub fn region_scope_of_return_scope(&self) -> region::Scope {
         // The outermost scope (`scopes[0]`) will be the `CallSiteScope`.
         // We want `scopes[1]`, which is the `ParameterScope`.
         assert!(self.scopes.len() >= 2);
-        assert!(match self.scopes[1].extent {
-            CodeExtent::ParameterScope(_) => true,
+        assert!(match self.scopes[1].region_scope {
+            region::Scope::Arguments(_) => true,
             _ => false,
         });
-        self.scopes[1].extent
+        self.scopes[1].region_scope
     }
 
     /// Returns the topmost active scope, which is known to be alive until
     /// the next scope expression.
-    pub fn topmost_scope(&self) -> CodeExtent {
-        self.scopes.last().expect("topmost_scope: no scopes present").extent
+    pub fn topmost_scope(&self) -> region::Scope {
+        self.scopes.last().expect("topmost_scope: no scopes present").region_scope
     }
 
     /// Returns the scope that we should use as the lifetime of an
@@ -457,7 +547,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
     ///
     /// When building statics/constants, returns `None` since
     /// intermediate values do not have to be dropped in that case.
-    pub fn local_scope(&self) -> Option<CodeExtent> {
+    pub fn local_scope(&self) -> Option<region::Scope> {
         match self.hir.src {
             MirSource::Const(_) |
             MirSource::Static(..) =>
@@ -465,7 +555,8 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                 None,
             MirSource::Fn(_) =>
                 Some(self.topmost_scope()),
-            MirSource::Promoted(..) =>
+            MirSource::Promoted(..) |
+            MirSource::GeneratorDrop(..) =>
                 bug!(),
         }
     }
@@ -473,15 +564,15 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
     // Scheduling drops
     // ================
     /// Indicates that `lvalue` should be dropped on exit from
-    /// `extent`.
+    /// `region_scope`.
     pub fn schedule_drop(&mut self,
                          span: Span,
-                         extent: CodeExtent,
+                         region_scope: region::Scope,
                          lvalue: &Lvalue<'tcx>,
                          lvalue_ty: Ty<'tcx>) {
         let needs_drop = self.hir.needs_drop(lvalue_ty);
         let drop_kind = if needs_drop {
-            DropKind::Value { cached_block: None }
+            DropKind::Value { cached_block: CachedBlock::default() }
         } else {
             // Only temps and vars need their storage dead.
             match *lvalue {
@@ -491,7 +582,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
         };
 
         for scope in self.scopes.iter_mut().rev() {
-            let this_scope = scope.extent == extent;
+            let this_scope = scope.region_scope == region_scope;
             // When building drops, we try to cache chains of drops in such a way so these drops
             // could be reused by the drops which would branch into the cached (already built)
             // blocks.  This, however, means that whenever we add a drop into a scope which already
@@ -544,10 +635,10 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                 if let DropKind::Value { .. } = drop_kind {
                     scope.needs_cleanup = true;
                 }
-                let tcx = self.hir.tcx();
-                let extent_span = extent.span(&tcx.hir).unwrap();
+                let region_scope_span = region_scope.span(self.hir.tcx(),
+                                                          &self.hir.region_scope_tree);
                 // Attribute scope exit drops to scope's closing brace
-                let scope_end = Span { lo: extent_span.hi, .. extent_span};
+                let scope_end = region_scope_span.with_lo(region_scope_span.hi());
                 scope.drops.push(DropData {
                     span: scope_end,
                     location: lvalue.clone(),
@@ -556,7 +647,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                 return;
             }
         }
-        span_bug!(span, "extent {:?} not in scope to drop {:?}", extent, lvalue);
+        span_bug!(span, "region scope {:?} not in scope to drop {:?}", region_scope, lvalue);
     }
 
     // Other
@@ -567,6 +658,10 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
     /// See module comment for more details. None indicates there’s no
     /// cleanup to do at this point.
     pub fn diverge_cleanup(&mut self) -> Option<BasicBlock> {
+        self.diverge_cleanup_gen(false)
+    }
+
+    fn diverge_cleanup_gen(&mut self, generator_drop: bool) -> Option<BasicBlock> {
         if !self.scopes.iter().any(|scope| scope.needs_cleanup) {
             return None;
         }
@@ -599,7 +694,8 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
         };
 
         for scope in scopes.iter_mut() {
-            target = build_diverge_scope(cfg, scope.extent_span, scope, target);
+            target = build_diverge_scope(cfg, scope.region_scope_span,
+                                         scope, target, generator_drop);
         }
         Some(target)
     }
@@ -676,7 +772,8 @@ fn build_scope_drops<'tcx>(cfg: &mut CFG<'tcx>,
                            scope: &Scope<'tcx>,
                            earlier_scopes: &[Scope<'tcx>],
                            mut block: BasicBlock,
-                           arg_count: usize)
+                           arg_count: usize,
+                           generator_drop: bool)
                            -> BlockAnd<()> {
     debug!("build_scope_drops({:?} -> {:?})", block, scope);
     let mut iter = scope.drops.iter().rev().peekable();
@@ -688,16 +785,20 @@ fn build_scope_drops<'tcx>(cfg: &mut CFG<'tcx>,
                 // for us to diverge into in case the drop panics.
                 let on_diverge = iter.peek().iter().filter_map(|dd| {
                     match dd.kind {
-                        DropKind::Value { cached_block: None } =>
-                            span_bug!(drop_data.span, "cached block not present?"),
-                        DropKind::Value { cached_block } => cached_block,
+                        DropKind::Value { cached_block } => {
+                            let result = cached_block.get(generator_drop);
+                            if result.is_none() {
+                                span_bug!(drop_data.span, "cached block not present?")
+                            }
+                            result
+                        },
                         DropKind::Storage => None
                     }
                 }).next();
                 // If there’s no `cached_block`s within current scope,
                 // we must look for one in the enclosing scope.
                 let on_diverge = on_diverge.or_else(|| {
-                    earlier_scopes.iter().rev().flat_map(|s| s.cached_block()).next()
+                    earlier_scopes.iter().rev().flat_map(|s| s.cached_block(generator_drop)).next()
                 });
                 let next = cfg.start_new_block();
                 cfg.terminate(block, source_info, TerminatorKind::Drop {
@@ -710,13 +811,18 @@ fn build_scope_drops<'tcx>(cfg: &mut CFG<'tcx>,
             DropKind::Storage => {}
         }
 
+        // We do not need to emit StorageDead for generator drops
+        if generator_drop {
+            continue
+        }
+
         // Drop the storage for both value and storage drops.
         // Only temps and vars need their storage dead.
         match drop_data.location {
             Lvalue::Local(index) if index.index() > arg_count => {
                 cfg.push(block, Statement {
                     source_info,
-                    kind: StatementKind::StorageDead(drop_data.location.clone())
+                    kind: StatementKind::StorageDead(index)
                 });
             }
             _ => continue
@@ -728,7 +834,8 @@ fn build_scope_drops<'tcx>(cfg: &mut CFG<'tcx>,
 fn build_diverge_scope<'a, 'gcx, 'tcx>(cfg: &mut CFG<'tcx>,
                                        span: Span,
                                        scope: &mut Scope<'tcx>,
-                                       mut target: BasicBlock)
+                                       mut target: BasicBlock,
+                                       generator_drop: bool)
                                        -> BasicBlock
 {
     // Build up the drops in **reverse** order. The end result will
@@ -742,7 +849,7 @@ fn build_diverge_scope<'a, 'gcx, 'tcx>(cfg: &mut CFG<'tcx>,
     // The code in this function reads from right to left. At each
     // point, we check for cached blocks representing the
     // remainder. If everything is cached, we'll just walk right to
-    // left reading the cached results but never created anything.
+    // left reading the cached results but never create anything.
 
     let visibility_scope = scope.visibility_scope;
     let source_info = |span| SourceInfo {
@@ -764,7 +871,7 @@ fn build_diverge_scope<'a, 'gcx, 'tcx>(cfg: &mut CFG<'tcx>,
         // match the behavior of clang, but on inspection eddyb says
         // this is not what clang does.
         let cached_block = match drop_data.kind {
-            DropKind::Value { ref mut cached_block } => cached_block,
+            DropKind::Value { ref mut cached_block } => cached_block.ref_mut(generator_drop),
             DropKind::Storage => continue
         };
         target = if let Some(cached_block) = *cached_block {
@@ -786,7 +893,7 @@ fn build_diverge_scope<'a, 'gcx, 'tcx>(cfg: &mut CFG<'tcx>,
     // becomes trivial goto after pass that removes all EndRegions.)
     {
         let block = cfg.start_new_cleanup_block();
-        cfg.push_end_region(block, source_info(span), scope.extent);
+        cfg.push_end_region(block, source_info(span), scope.region_scope);
         cfg.terminate(block, source_info(span), TerminatorKind::Goto { target: target });
         target = block
     }
diff --git a/src/librustc_mir/dataflow/impls/borrows.rs b/src/librustc_mir/dataflow/impls/borrows.rs
index ab62342e607dd..3f815ec83e3a5 100644
--- a/src/librustc_mir/dataflow/impls/borrows.rs
+++ b/src/librustc_mir/dataflow/impls/borrows.rs
@@ -107,7 +107,7 @@ impl<'a, 'tcx> BitDenotation for Borrows<'a, 'tcx> {
         self.borrows.len()
     }
     fn start_block_effect(&self, _sets: &mut BlockSets<BorrowIndex>)  {
-        // no borrows of code extents have been taken prior to
+        // no borrows of code region_scopes have been taken prior to
         // function execution, so this method has no effect on
         // `_sets`.
     }
@@ -121,9 +121,9 @@ impl<'a, 'tcx> BitDenotation for Borrows<'a, 'tcx> {
             panic!("could not find statement at location {:?}");
         });
         match stmt.kind {
-            mir::StatementKind::EndRegion(extent) => {
-                let borrow_indexes = self.region_map.get(&ReScope(extent)).unwrap_or_else(|| {
-                    panic!("could not find BorrowIndexs for code-extent {:?}", extent);
+            mir::StatementKind::EndRegion(region_scope) => {
+                let borrow_indexes = self.region_map.get(&ReScope(region_scope)).unwrap_or_else(|| {
+                    panic!("could not find BorrowIndexs for region scope {:?}", region_scope);
                 });
 
                 for idx in borrow_indexes { sets.kill(&idx); }
@@ -153,7 +153,7 @@ impl<'a, 'tcx> BitDenotation for Borrows<'a, 'tcx> {
     fn terminator_effect(&self,
                          _sets: &mut BlockSets<BorrowIndex>,
                          _location: Location) {
-        // no terminators start nor end code extents.
+        // no terminators start nor end region scopes.
     }
 
     fn propagate_call_return(&self,
@@ -161,7 +161,7 @@ impl<'a, 'tcx> BitDenotation for Borrows<'a, 'tcx> {
                              _call_bb: mir::BasicBlock,
                              _dest_bb: mir::BasicBlock,
                              _dest_lval: &mir::Lvalue) {
-        // there are no effects on the extents from method calls.
+        // there are no effects on the region scopes from method calls.
     }
 }
 
diff --git a/src/librustc_mir/dataflow/mod.rs b/src/librustc_mir/dataflow/mod.rs
index 237795491b186..9f9909a8f57a9 100644
--- a/src/librustc_mir/dataflow/mod.rs
+++ b/src/librustc_mir/dataflow/mod.rs
@@ -653,15 +653,21 @@ impl<'a, 'tcx: 'a, D> DataflowAnalysis<'a, 'tcx, D> where D: BitDenotation
         match bb_data.terminator().kind {
             mir::TerminatorKind::Return |
             mir::TerminatorKind::Resume |
+            mir::TerminatorKind::GeneratorDrop |
             mir::TerminatorKind::Unreachable => {}
             mir::TerminatorKind::Goto { ref target } |
             mir::TerminatorKind::Assert { ref target, cleanup: None, .. } |
+            mir::TerminatorKind::Yield { resume: ref target, drop: None, .. } |
             mir::TerminatorKind::Drop { ref target, location: _, unwind: None } |
             mir::TerminatorKind::DropAndReplace {
                 ref target, value: _, location: _, unwind: None
             } => {
                 self.propagate_bits_into_entry_set_for(in_out, changed, target);
             }
+            mir::TerminatorKind::Yield { resume: ref target, drop: Some(ref drop), .. } => {
+                self.propagate_bits_into_entry_set_for(in_out, changed, target);
+                self.propagate_bits_into_entry_set_for(in_out, changed, drop);
+            }
             mir::TerminatorKind::Assert { ref target, cleanup: Some(ref unwind), .. } |
             mir::TerminatorKind::Drop { ref target, location: _, unwind: Some(ref unwind) } |
             mir::TerminatorKind::DropAndReplace {
diff --git a/src/librustc_mir/dataflow/move_paths/abs_domain.rs b/src/librustc_mir/dataflow/move_paths/abs_domain.rs
index 173396f22457a..00825c7a880e9 100644
--- a/src/librustc_mir/dataflow/move_paths/abs_domain.rs
+++ b/src/librustc_mir/dataflow/move_paths/abs_domain.rs
@@ -21,8 +21,7 @@
 //! `a[x]` would still overlap them both. But that is not this
 //! representation does today.)
 
-use rustc::mir::LvalueElem;
-use rustc::mir::{Operand, ProjectionElem};
+use rustc::mir::{Local, LvalueElem, Operand, ProjectionElem};
 use rustc::ty::Ty;
 
 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
@@ -40,6 +39,10 @@ impl<'tcx> Lift for Operand<'tcx> {
     type Abstract = AbstractOperand;
     fn lift(&self) -> Self::Abstract { AbstractOperand }
 }
+impl Lift for Local {
+    type Abstract = AbstractOperand;
+    fn lift(&self) -> Self::Abstract { AbstractOperand }
+}
 impl<'tcx> Lift for Ty<'tcx> {
     type Abstract = AbstractType;
     fn lift(&self) -> Self::Abstract { AbstractType }
diff --git a/src/librustc_mir/dataflow/move_paths/builder.rs b/src/librustc_mir/dataflow/move_paths/builder.rs
index c45c91011d9f4..86298c3b83e29 100644
--- a/src/librustc_mir/dataflow/move_paths/builder.rs
+++ b/src/librustc_mir/dataflow/move_paths/builder.rs
@@ -263,6 +263,7 @@ impl<'a, 'tcx> MoveDataBuilder<'a, 'tcx> {
         match term.kind {
             TerminatorKind::Goto { target: _ } |
             TerminatorKind::Resume |
+            TerminatorKind::GeneratorDrop |
             TerminatorKind::Unreachable => { }
 
             TerminatorKind::Return => {
@@ -274,6 +275,10 @@ impl<'a, 'tcx> MoveDataBuilder<'a, 'tcx> {
                 // branching terminators - these don't move anything
             }
 
+            TerminatorKind::Yield { ref value, .. } => {
+                self.gather_operand(loc, value);
+            }
+
             TerminatorKind::Drop { ref location, target: _, unwind: _ } => {
                 self.gather_move(loc, location);
             }
diff --git a/src/librustc_mir/hair/cx/block.rs b/src/librustc_mir/hair/cx/block.rs
index 61d128fc84782..8b3031a3800a5 100644
--- a/src/librustc_mir/hair/cx/block.rs
+++ b/src/librustc_mir/hair/cx/block.rs
@@ -11,9 +11,8 @@
 use hair::*;
 use hair::cx::Cx;
 use hair::cx::to_ref::ToRef;
-use rustc::middle::region::{BlockRemainder, CodeExtent};
+use rustc::middle::region::{self, BlockRemainder};
 use rustc::hir;
-use syntax::ast;
 
 impl<'tcx> Mirror<'tcx> for &'tcx hir::Block {
     type Output = Block<'tcx>;
@@ -21,12 +20,13 @@ impl<'tcx> Mirror<'tcx> for &'tcx hir::Block {
     fn make_mirror<'a, 'gcx>(self, cx: &mut Cx<'a, 'gcx, 'tcx>) -> Block<'tcx> {
         // We have to eagerly translate the "spine" of the statements
         // in order to get the lexical scoping correctly.
-        let stmts = mirror_stmts(cx, self.id, &*self.stmts);
-        let opt_destruction_extent = cx.region_maps.opt_destruction_extent(self.id);
+        let stmts = mirror_stmts(cx, self.hir_id.local_id, &*self.stmts);
+        let opt_destruction_scope =
+            cx.region_scope_tree.opt_destruction_scope(self.hir_id.local_id);
         Block {
             targeted_by_break: self.targeted_by_break,
-            extent: CodeExtent::Misc(self.id),
-            opt_destruction_extent,
+            region_scope: region::Scope::Node(self.hir_id.local_id),
+            opt_destruction_scope,
             span: self.span,
             stmts,
             expr: self.expr.to_ref(),
@@ -35,31 +35,31 @@ impl<'tcx> Mirror<'tcx> for &'tcx hir::Block {
 }
 
 fn mirror_stmts<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
-                                block_id: ast::NodeId,
+                                block_id: hir::ItemLocalId,
                                 stmts: &'tcx [hir::Stmt])
                                 -> Vec<StmtRef<'tcx>> {
     let mut result = vec![];
     for (index, stmt) in stmts.iter().enumerate() {
-        let opt_dxn_ext = cx.region_maps.opt_destruction_extent(stmt.node.id());
+        let hir_id = cx.tcx.hir.node_to_hir_id(stmt.node.id());
+        let opt_dxn_ext = cx.region_scope_tree.opt_destruction_scope(hir_id.local_id);
         match stmt.node {
-            hir::StmtExpr(ref expr, id) |
-            hir::StmtSemi(ref expr, id) => {
+            hir::StmtExpr(ref expr, _) |
+            hir::StmtSemi(ref expr, _) => {
                 result.push(StmtRef::Mirror(Box::new(Stmt {
-                    span: stmt.span,
                     kind: StmtKind::Expr {
-                        scope: CodeExtent::Misc(id),
+                        scope: region::Scope::Node(hir_id.local_id),
                         expr: expr.to_ref(),
                     },
-                    opt_destruction_extent: opt_dxn_ext,
+                    opt_destruction_scope: opt_dxn_ext,
                 })))
             }
-            hir::StmtDecl(ref decl, id) => {
+            hir::StmtDecl(ref decl, _) => {
                 match decl.node {
                     hir::DeclItem(..) => {
                         // ignore for purposes of the MIR
                     }
                     hir::DeclLocal(ref local) => {
-                        let remainder_extent = CodeExtent::Remainder(BlockRemainder {
+                        let remainder_scope = region::Scope::Remainder(BlockRemainder {
                             block: block_id,
                             first_statement_index: index as u32,
                         });
@@ -69,14 +69,13 @@ fn mirror_stmts<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
                                                         cx.tables(),
                                                         &local.pat);
                         result.push(StmtRef::Mirror(Box::new(Stmt {
-                            span: stmt.span,
                             kind: StmtKind::Let {
-                                remainder_scope: remainder_extent,
-                                init_scope: CodeExtent::Misc(id),
+                                remainder_scope: remainder_scope,
+                                init_scope: region::Scope::Node(hir_id.local_id),
                                 pattern,
                                 initializer: local.init.to_ref(),
                             },
-                            opt_destruction_extent: opt_dxn_ext,
+                            opt_destruction_scope: opt_dxn_ext,
                         })));
                     }
                 }
@@ -90,7 +89,7 @@ pub fn to_expr_ref<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
                                    block: &'tcx hir::Block)
                                    -> ExprRef<'tcx> {
     let block_ty = cx.tables().node_id_to_type(block.hir_id);
-    let temp_lifetime = cx.region_maps.temporary_scope(block.id);
+    let temp_lifetime = cx.region_scope_tree.temporary_scope(block.hir_id.local_id);
     let expr = Expr {
         ty: block_ty,
         temp_lifetime,
diff --git a/src/librustc_mir/hair/cx/expr.rs b/src/librustc_mir/hair/cx/expr.rs
index 944fb8e83329b..c96d42b94f975 100644
--- a/src/librustc_mir/hair/cx/expr.rs
+++ b/src/librustc_mir/hair/cx/expr.rs
@@ -25,8 +25,8 @@ impl<'tcx> Mirror<'tcx> for &'tcx hir::Expr {
     type Output = Expr<'tcx>;
 
     fn make_mirror<'a, 'gcx>(self, cx: &mut Cx<'a, 'gcx, 'tcx>) -> Expr<'tcx> {
-        let temp_lifetime = cx.region_maps.temporary_scope(self.id);
-        let expr_extent = CodeExtent::Misc(self.id);
+        let temp_lifetime = cx.region_scope_tree.temporary_scope(self.hir_id.local_id);
+        let expr_scope = region::Scope::Node(self.hir_id.local_id);
 
         debug!("Expr::make_mirror(): id={}, span={:?}", self.id, self.span);
 
@@ -46,19 +46,20 @@ impl<'tcx> Mirror<'tcx> for &'tcx hir::Expr {
             ty: expr.ty,
             span: self.span,
             kind: ExprKind::Scope {
-                extent: expr_extent,
+                region_scope: expr_scope,
                 value: expr.to_ref(),
             },
         };
 
         // Finally, create a destruction scope, if any.
-        if let Some(extent) = cx.region_maps.opt_destruction_extent(self.id) {
+        if let Some(region_scope) =
+                cx.region_scope_tree.opt_destruction_scope(self.hir_id.local_id) {
             expr = Expr {
                 temp_lifetime,
                 ty: expr.ty,
                 span: self.span,
                 kind: ExprKind::Scope {
-                    extent,
+                    region_scope,
                     value: expr.to_ref(),
                 },
             };
@@ -125,7 +126,7 @@ fn apply_adjustment<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
             // Convert this to a suitable `&foo` and
             // then an unsafe coercion. Limit the region to be just this
             // expression.
-            let region = ty::ReScope(CodeExtent::Misc(hir_expr.id));
+            let region = ty::ReScope(region::Scope::Node(hir_expr.hir_id.local_id));
             let region = cx.tcx.mk_region(region);
             expr = Expr {
                 temp_lifetime,
@@ -160,7 +161,7 @@ fn make_mirror_unadjusted<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
                                           expr: &'tcx hir::Expr)
                                           -> Expr<'tcx> {
     let expr_ty = cx.tables().expr_ty(expr);
-    let temp_lifetime = cx.region_maps.temporary_scope(expr.id);
+    let temp_lifetime = cx.region_scope_tree.temporary_scope(expr.hir_id.local_id);
 
     let kind = match expr.node {
         // Here comes the interesting stuff:
@@ -432,8 +433,9 @@ fn make_mirror_unadjusted<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
 
         hir::ExprClosure(..) => {
             let closure_ty = cx.tables().expr_ty(expr);
-            let (def_id, substs) = match closure_ty.sty {
-                ty::TyClosure(def_id, substs) => (def_id, substs),
+            let (def_id, substs, interior) = match closure_ty.sty {
+                ty::TyClosure(def_id, substs) => (def_id, substs, None),
+                ty::TyGenerator(def_id, substs, interior) => (def_id, substs, Some(interior)),
                 _ => {
                     span_bug!(expr.span, "closure expr w/o closure type: {:?}", closure_ty);
                 }
@@ -448,6 +450,7 @@ fn make_mirror_unadjusted<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
                 closure_id: def_id,
                 substs,
                 upvars,
+                interior,
             }
         }
 
@@ -485,7 +488,7 @@ fn make_mirror_unadjusted<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
             match dest.target_id {
                 hir::ScopeTarget::Block(target_id) |
                 hir::ScopeTarget::Loop(hir::LoopIdResult::Ok(target_id)) => ExprKind::Break {
-                    label: CodeExtent::Misc(target_id),
+                    label: region::Scope::Node(cx.tcx.hir.node_to_hir_id(target_id).local_id),
                     value: value.to_ref(),
                 },
                 hir::ScopeTarget::Loop(hir::LoopIdResult::Err(err)) =>
@@ -496,7 +499,7 @@ fn make_mirror_unadjusted<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
             match dest.target_id {
                 hir::ScopeTarget::Block(_) => bug!("cannot continue to blocks"),
                 hir::ScopeTarget::Loop(hir::LoopIdResult::Ok(loop_id)) => ExprKind::Continue {
-                    label: CodeExtent::Misc(loop_id),
+                    label: region::Scope::Node(cx.tcx.hir.node_to_hir_id(loop_id).local_id),
                 },
                 hir::ScopeTarget::Loop(hir::LoopIdResult::Err(err)) =>
                     bug!("invalid loop id for continue: {}", err)
@@ -567,6 +570,8 @@ fn make_mirror_unadjusted<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
         }
         hir::ExprArray(ref fields) => ExprKind::Array { fields: fields.to_ref() },
         hir::ExprTup(ref fields) => ExprKind::Tuple { fields: fields.to_ref() },
+
+        hir::ExprYield(ref v) => ExprKind::Yield { value: v.to_ref() },
     };
 
     Expr {
@@ -581,7 +586,7 @@ fn method_callee<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
                                  expr: &hir::Expr,
                                  custom_callee: Option<(DefId, &'tcx Substs<'tcx>)>)
                                  -> Expr<'tcx> {
-    let temp_lifetime = cx.region_maps.temporary_scope(expr.id);
+    let temp_lifetime = cx.region_scope_tree.temporary_scope(expr.hir_id.local_id);
     let (def_id, substs) = custom_callee.unwrap_or_else(|| {
         (cx.tables().type_dependent_defs()[expr.hir_id].def_id(),
          cx.tables().node_substs(expr.hir_id))
@@ -672,7 +677,7 @@ fn convert_var<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
                                expr: &'tcx hir::Expr,
                                def: Def)
                                -> ExprKind<'tcx> {
-    let temp_lifetime = cx.region_maps.temporary_scope(expr.id);
+    let temp_lifetime = cx.region_scope_tree.temporary_scope(expr.hir_id.local_id);
 
     match def {
         Def::Local(def_id) => {
@@ -703,56 +708,65 @@ fn convert_var<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
             });
             let region = cx.tcx.mk_region(region);
 
-            let self_expr = match cx.tcx.closure_kind(closure_def_id) {
-                ty::ClosureKind::Fn => {
-                    let ref_closure_ty = cx.tcx.mk_ref(region,
-                                                       ty::TypeAndMut {
-                                                           ty: closure_ty,
-                                                           mutbl: hir::MutImmutable,
-                                                       });
-                    Expr {
-                        ty: closure_ty,
-                        temp_lifetime,
-                        span: expr.span,
-                        kind: ExprKind::Deref {
-                            arg: Expr {
-                                ty: ref_closure_ty,
-                                temp_lifetime,
-                                span: expr.span,
-                                kind: ExprKind::SelfRef,
-                            }
-                            .to_ref(),
-                        },
+            let self_expr = if let ty::TyClosure(..) = closure_ty.sty {
+                match cx.tcx.closure_kind(closure_def_id) {
+                    ty::ClosureKind::Fn => {
+                        let ref_closure_ty = cx.tcx.mk_ref(region,
+                                                           ty::TypeAndMut {
+                                                               ty: closure_ty,
+                                                               mutbl: hir::MutImmutable,
+                                                           });
+                        Expr {
+                            ty: closure_ty,
+                            temp_lifetime: temp_lifetime,
+                            span: expr.span,
+                            kind: ExprKind::Deref {
+                                arg: Expr {
+                                    ty: ref_closure_ty,
+                                    temp_lifetime,
+                                    span: expr.span,
+                                    kind: ExprKind::SelfRef,
+                                }
+                                .to_ref(),
+                            },
+                        }
                     }
-                }
-                ty::ClosureKind::FnMut => {
-                    let ref_closure_ty = cx.tcx.mk_ref(region,
-                                                       ty::TypeAndMut {
-                                                           ty: closure_ty,
-                                                           mutbl: hir::MutMutable,
-                                                       });
-                    Expr {
-                        ty: closure_ty,
-                        temp_lifetime,
-                        span: expr.span,
-                        kind: ExprKind::Deref {
-                            arg: Expr {
-                                ty: ref_closure_ty,
-                                temp_lifetime,
-                                span: expr.span,
-                                kind: ExprKind::SelfRef,
-                            }.to_ref(),
-                        },
+                    ty::ClosureKind::FnMut => {
+                        let ref_closure_ty = cx.tcx.mk_ref(region,
+                                                           ty::TypeAndMut {
+                                                               ty: closure_ty,
+                                                               mutbl: hir::MutMutable,
+                                                           });
+                        Expr {
+                            ty: closure_ty,
+                            temp_lifetime,
+                            span: expr.span,
+                            kind: ExprKind::Deref {
+                                arg: Expr {
+                                    ty: ref_closure_ty,
+                                    temp_lifetime,
+                                    span: expr.span,
+                                    kind: ExprKind::SelfRef,
+                                }.to_ref(),
+                            },
+                        }
                     }
-                }
-                ty::ClosureKind::FnOnce => {
-                    Expr {
-                        ty: closure_ty,
-                        temp_lifetime,
-                        span: expr.span,
-                        kind: ExprKind::SelfRef,
+                    ty::ClosureKind::FnOnce => {
+                        Expr {
+                            ty: closure_ty,
+                            temp_lifetime,
+                            span: expr.span,
+                            kind: ExprKind::SelfRef,
+                        }
                     }
                 }
+            } else {
+                Expr {
+                    ty: closure_ty,
+                    temp_lifetime,
+                    span: expr.span,
+                    kind: ExprKind::SelfRef,
+                }
             };
 
             // at this point we have `self.n`, which loads up the upvar
@@ -854,7 +868,7 @@ fn overloaded_lvalue<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
 
     // construct the complete expression `foo()` for the overloaded call,
     // which will yield the &T type
-    let temp_lifetime = cx.region_maps.temporary_scope(expr.id);
+    let temp_lifetime = cx.region_scope_tree.temporary_scope(expr.hir_id.local_id);
     let fun = method_callee(cx, expr, custom_callee);
     let ref_expr = Expr {
         temp_lifetime,
@@ -883,7 +897,7 @@ fn capture_freevar<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
         closure_expr_id: cx.tcx.hir.local_def_id(closure_expr.id).index,
     };
     let upvar_capture = cx.tables().upvar_capture(upvar_id);
-    let temp_lifetime = cx.region_maps.temporary_scope(closure_expr.id);
+    let temp_lifetime = cx.region_scope_tree.temporary_scope(closure_expr.hir_id.local_id);
     let var_ty = cx.tables()
                    .node_id_to_type(cx.tcx.hir.node_to_hir_id(var_node_id));
     let captured_var = Expr {
diff --git a/src/librustc_mir/hair/cx/mod.rs b/src/librustc_mir/hair/cx/mod.rs
index 2f4ab36d394b0..3cabd8f18c19e 100644
--- a/src/librustc_mir/hair/cx/mod.rs
+++ b/src/librustc_mir/hair/cx/mod.rs
@@ -22,7 +22,7 @@ use rustc_const_eval::ConstContext;
 use rustc_data_structures::indexed_vec::Idx;
 use rustc::hir::def_id::DefId;
 use rustc::hir::map::blocks::FnLikeNode;
-use rustc::middle::region::RegionMaps;
+use rustc::middle::region;
 use rustc::infer::InferCtxt;
 use rustc::ty::subst::Subst;
 use rustc::ty::{self, Ty, TyCtxt};
@@ -42,7 +42,7 @@ pub struct Cx<'a, 'gcx: 'a + 'tcx, 'tcx: 'a> {
     /// Identity `Substs` for use with const-evaluation.
     pub identity_substs: &'gcx Substs<'gcx>,
 
-    pub region_maps: Rc<RegionMaps>,
+    pub region_scope_tree: Rc<region::ScopeTree>,
     pub tables: &'a ty::TypeckTables<'gcx>,
 
     /// This is `Constness::Const` if we are compiling a `static`,
@@ -61,6 +61,7 @@ impl<'a, 'gcx, 'tcx> Cx<'a, 'gcx, 'tcx> {
         let constness = match src {
             MirSource::Const(_) |
             MirSource::Static(..) => hir::Constness::Const,
+            MirSource::GeneratorDrop(..) => hir::Constness::NotConst,
             MirSource::Fn(id) => {
                 let fn_like = FnLikeNode::from_node(infcx.tcx.hir.get(id));
                 fn_like.map_or(hir::Constness::NotConst, |f| f.constness())
@@ -91,7 +92,7 @@ impl<'a, 'gcx, 'tcx> Cx<'a, 'gcx, 'tcx> {
             infcx,
             param_env: tcx.param_env(src_def_id),
             identity_substs: Substs::identity_for_item(tcx.global_tcx(), src_def_id),
-            region_maps: tcx.region_maps(src_def_id),
+            region_scope_tree: tcx.region_scope_tree(src_def_id),
             tables: tcx.typeck_tables_of(src_def_id),
             constness,
             src,
diff --git a/src/librustc_mir/hair/mod.rs b/src/librustc_mir/hair/mod.rs
index 01faa61d0964a..067bd458d97dd 100644
--- a/src/librustc_mir/hair/mod.rs
+++ b/src/librustc_mir/hair/mod.rs
@@ -17,9 +17,9 @@
 use rustc_const_math::ConstUsize;
 use rustc::mir::{BinOp, BorrowKind, Field, Literal, UnOp};
 use rustc::hir::def_id::DefId;
-use rustc::middle::region::CodeExtent;
+use rustc::middle::region;
 use rustc::ty::subst::Substs;
-use rustc::ty::{self, AdtDef, ClosureSubsts, Region, Ty};
+use rustc::ty::{self, AdtDef, ClosureSubsts, Region, Ty, GeneratorInterior};
 use rustc::hir;
 use syntax::ast;
 use syntax_pos::Span;
@@ -32,8 +32,8 @@ pub use rustc_const_eval::pattern::{BindingMode, Pattern, PatternKind, FieldPatt
 #[derive(Clone, Debug)]
 pub struct Block<'tcx> {
     pub targeted_by_break: bool,
-    pub extent: CodeExtent,
-    pub opt_destruction_extent: Option<CodeExtent>,
+    pub region_scope: region::Scope,
+    pub opt_destruction_scope: Option<region::Scope>,
     pub span: Span,
     pub stmts: Vec<StmtRef<'tcx>>,
     pub expr: Option<ExprRef<'tcx>>,
@@ -46,16 +46,15 @@ pub enum StmtRef<'tcx> {
 
 #[derive(Clone, Debug)]
 pub struct Stmt<'tcx> {
-    pub span: Span,
     pub kind: StmtKind<'tcx>,
-    pub opt_destruction_extent: Option<CodeExtent>,
+    pub opt_destruction_scope: Option<region::Scope>,
 }
 
 #[derive(Clone, Debug)]
 pub enum StmtKind<'tcx> {
     Expr {
         /// scope for this statement; may be used as lifetime of temporaries
-        scope: CodeExtent,
+        scope: region::Scope,
 
         /// expression being evaluated in this statement
         expr: ExprRef<'tcx>,
@@ -64,11 +63,11 @@ pub enum StmtKind<'tcx> {
     Let {
         /// scope for variables bound in this let; covers this and
         /// remaining statements in block
-        remainder_scope: CodeExtent,
+        remainder_scope: region::Scope,
 
         /// scope for the initialization itself; might be used as
         /// lifetime of temporaries
-        init_scope: CodeExtent,
+        init_scope: region::Scope,
 
         /// let <PAT> = ...
         pattern: Pattern<'tcx>,
@@ -99,7 +98,7 @@ pub struct Expr<'tcx> {
 
     /// lifetime of this expression if it should be spilled into a
     /// temporary; should be None only if in a constant context
-    pub temp_lifetime: Option<CodeExtent>,
+    pub temp_lifetime: Option<region::Scope>,
 
     /// span of the expression in the source
     pub span: Span,
@@ -111,7 +110,7 @@ pub struct Expr<'tcx> {
 #[derive(Clone, Debug)]
 pub enum ExprKind<'tcx> {
     Scope {
-        extent: CodeExtent,
+        region_scope: region::Scope,
         value: ExprRef<'tcx>,
     },
     Box {
@@ -208,11 +207,11 @@ pub enum ExprKind<'tcx> {
         arg: ExprRef<'tcx>,
     },
     Break {
-        label: CodeExtent,
+        label: region::Scope,
         value: Option<ExprRef<'tcx>>,
     },
     Continue {
-        label: CodeExtent,
+        label: region::Scope,
     },
     Return {
         value: Option<ExprRef<'tcx>>,
@@ -238,6 +237,7 @@ pub enum ExprKind<'tcx> {
         closure_id: DefId,
         substs: ClosureSubsts<'tcx>,
         upvars: Vec<ExprRef<'tcx>>,
+        interior: Option<GeneratorInterior<'tcx>>,
     },
     Literal {
         literal: Literal<'tcx>,
@@ -247,6 +247,9 @@ pub enum ExprKind<'tcx> {
         outputs: Vec<ExprRef<'tcx>>,
         inputs: Vec<ExprRef<'tcx>>
     },
+    Yield {
+        value: ExprRef<'tcx>,
+    },
 }
 
 #[derive(Clone, Debug)]
diff --git a/src/librustc_mir/shim.rs b/src/librustc_mir/shim.rs
index 6bee1ceff89fb..d3c886dab4e86 100644
--- a/src/librustc_mir/shim.rs
+++ b/src/librustc_mir/shim.rs
@@ -140,6 +140,7 @@ fn temp_decl(mutability: Mutability, ty: Ty, span: Span) -> LocalDecl {
     LocalDecl {
         mutability, ty, name: None,
         source_info: SourceInfo { scope: ARGUMENT_VISIBILITY_SCOPE, span },
+        internal: false,
         is_user_variable: false
     }
 }
@@ -160,6 +161,12 @@ fn build_drop_shim<'a, 'tcx>(tcx: ty::TyCtxt<'a, 'tcx, 'tcx>,
 {
     debug!("build_drop_shim(def_id={:?}, ty={:?})", def_id, ty);
 
+    // Check if this is a generator, if so, return the drop glue for it
+    if let Some(&ty::TyS { sty: ty::TyGenerator(gen_def_id, substs, _), .. }) = ty {
+        let mir = &**tcx.optimized_mir(gen_def_id).generator_drop.as_ref().unwrap();
+        return mir.subst(tcx, substs.substs);
+    }
+
     let substs = if let Some(ty) = ty {
         tcx.mk_substs(iter::once(Kind::from(ty)))
     } else {
@@ -190,6 +197,7 @@ fn build_drop_shim<'a, 'tcx>(tcx: ty::TyCtxt<'a, 'tcx, 'tcx>,
         ),
         IndexVec::new(),
         sig.output(),
+        None,
         local_decls_for_sig(&sig, span),
         sig.inputs().len(),
         vec![],
@@ -225,10 +233,10 @@ fn build_drop_shim<'a, 'tcx>(tcx: ty::TyCtxt<'a, 'tcx, 'tcx>,
 }
 
 pub struct DropShimElaborator<'a, 'tcx: 'a> {
-    mir: &'a Mir<'tcx>,
-    patch: MirPatch<'tcx>,
-    tcx: ty::TyCtxt<'a, 'tcx, 'tcx>,
-    param_env: ty::ParamEnv<'tcx>,
+    pub mir: &'a Mir<'tcx>,
+    pub patch: MirPatch<'tcx>,
+    pub tcx: ty::TyCtxt<'a, 'tcx, 'tcx>,
+    pub param_env: ty::ParamEnv<'tcx>,
 }
 
 impl<'a, 'tcx> fmt::Debug for DropShimElaborator<'a, 'tcx> {
@@ -327,6 +335,7 @@ impl<'a, 'tcx> CloneShimBuilder<'a, 'tcx> {
             ),
             IndexVec::new(),
             self.sig.output(),
+            None,
             self.local_decls,
             self.sig.inputs().len(),
             vec![],
@@ -470,9 +479,10 @@ impl<'a, 'tcx> CloneShimBuilder<'a, 'tcx> {
 
     fn array_shim(&mut self, ty: ty::Ty<'tcx>, len: usize) {
         let tcx = self.tcx;
+        let span = self.span;
         let rcvr = Lvalue::Local(Local::new(1+0)).deref();
 
-        let beg = self.make_lvalue(Mutability::Mut, tcx.types.usize);
+        let beg = self.local_decls.push(temp_decl(Mutability::Mut, tcx.types.usize, span));
         let end = self.make_lvalue(Mutability::Not, tcx.types.usize);
         let ret = self.make_lvalue(Mutability::Mut, tcx.mk_array(ty, len));
 
@@ -483,7 +493,7 @@ impl<'a, 'tcx> CloneShimBuilder<'a, 'tcx> {
         let inits = vec![
             self.make_statement(
                 StatementKind::Assign(
-                    beg.clone(),
+                    Lvalue::Local(beg),
                     Rvalue::Use(Operand::Constant(self.make_usize(0)))
                 )
             ),
@@ -501,19 +511,19 @@ impl<'a, 'tcx> CloneShimBuilder<'a, 'tcx> {
         //     BB #3;
         // }
         // BB #4;
-        self.loop_header(beg.clone(), end, BasicBlock::new(2), BasicBlock::new(4), false);
+        self.loop_header(Lvalue::Local(beg), end, BasicBlock::new(2), BasicBlock::new(4), false);
 
         // BB #2
         // `let cloned = Clone::clone(rcvr[beg])`;
         // Goto #3 if ok, #5 if unwinding happens.
-        let rcvr_field = rcvr.clone().index(Operand::Consume(beg.clone()));
+        let rcvr_field = rcvr.clone().index(beg);
         let cloned = self.make_clone_call(ty, rcvr_field, BasicBlock::new(3), BasicBlock::new(5));
 
         // BB #3
         // `ret[beg] = cloned;`
         // `beg = beg + 1;`
         // `goto #1`;
-        let ret_field = ret.clone().index(Operand::Consume(beg.clone()));
+        let ret_field = ret.clone().index(beg);
         let statements = vec![
             self.make_statement(
                 StatementKind::Assign(
@@ -523,10 +533,10 @@ impl<'a, 'tcx> CloneShimBuilder<'a, 'tcx> {
             ),
             self.make_statement(
                 StatementKind::Assign(
-                    beg.clone(),
+                    Lvalue::Local(beg),
                     Rvalue::BinaryOp(
                         BinOp::Add,
-                        Operand::Consume(beg.clone()),
+                        Operand::Consume(Lvalue::Local(beg)),
                         Operand::Constant(self.make_usize(1))
                     )
                 )
@@ -549,10 +559,10 @@ impl<'a, 'tcx> CloneShimBuilder<'a, 'tcx> {
         // `let mut beg = 0;`
         // goto #6;
         let end = beg;
-        let beg = self.make_lvalue(Mutability::Mut, tcx.types.usize);
+        let beg = self.local_decls.push(temp_decl(Mutability::Mut, tcx.types.usize, span));
         let init = self.make_statement(
             StatementKind::Assign(
-                beg.clone(),
+                Lvalue::Local(beg),
                 Rvalue::Use(Operand::Constant(self.make_usize(0)))
             )
         );
@@ -563,12 +573,13 @@ impl<'a, 'tcx> CloneShimBuilder<'a, 'tcx> {
         //     BB #8;
         // }
         // BB #9;
-        self.loop_header(beg.clone(), end, BasicBlock::new(7), BasicBlock::new(9), true);
+        self.loop_header(Lvalue::Local(beg), Lvalue::Local(end),
+                         BasicBlock::new(7), BasicBlock::new(9), true);
 
         // BB #7 (cleanup)
         // `drop(ret[beg])`;
         self.block(vec![], TerminatorKind::Drop {
-            location: ret.index(Operand::Consume(beg.clone())),
+            location: ret.index(beg),
             target: BasicBlock::new(8),
             unwind: None,
         }, true);
@@ -578,10 +589,10 @@ impl<'a, 'tcx> CloneShimBuilder<'a, 'tcx> {
         // `goto #6;`
         let statement = self.make_statement(
             StatementKind::Assign(
-                beg.clone(),
+                Lvalue::Local(beg),
                 Rvalue::BinaryOp(
                     BinOp::Add,
-                    Operand::Consume(beg.clone()),
+                    Operand::Consume(Lvalue::Local(beg)),
                     Operand::Constant(self.make_usize(1))
                 )
             )
@@ -770,6 +781,7 @@ fn build_call_shim<'a, 'tcx>(tcx: ty::TyCtxt<'a, 'tcx, 'tcx>,
         ),
         IndexVec::new(),
         sig.output(),
+        None,
         local_decls,
         sig.inputs().len(),
         vec![],
@@ -841,6 +853,7 @@ pub fn build_adt_ctor<'a, 'gcx, 'tcx>(infcx: &infer::InferCtxt<'a, 'gcx, 'tcx>,
         ),
         IndexVec::new(),
         sig.output(),
+        None,
         local_decls,
         sig.inputs().len(),
         vec![],
diff --git a/src/librustc_mir/transform/add_validation.rs b/src/librustc_mir/transform/add_validation.rs
index 52c2eaa7cb632..8fad538af97ba 100644
--- a/src/librustc_mir/transform/add_validation.rs
+++ b/src/librustc_mir/transform/add_validation.rs
@@ -18,7 +18,7 @@ use rustc::ty::{self, TyCtxt, RegionKind};
 use rustc::hir;
 use rustc::mir::*;
 use rustc::mir::transform::{MirPass, MirSource};
-use rustc::middle::region::CodeExtent;
+use rustc::middle::region;
 
 pub struct AddValidation;
 
@@ -27,7 +27,7 @@ fn lval_context<'a, 'tcx, D>(
     lval: &Lvalue<'tcx>,
     local_decls: &D,
     tcx: TyCtxt<'a, 'tcx, 'tcx>
-) -> (Option<CodeExtent>, hir::Mutability)
+) -> (Option<region::Scope>, hir::Mutability)
     where D: HasLocalDecls<'tcx>
 {
     use rustc::mir::Lvalue::*;
diff --git a/src/librustc_mir/transform/clean_end_regions.rs b/src/librustc_mir/transform/clean_end_regions.rs
index f06b88551d11d..55a16b2f39161 100644
--- a/src/librustc_mir/transform/clean_end_regions.rs
+++ b/src/librustc_mir/transform/clean_end_regions.rs
@@ -21,7 +21,7 @@
 
 use rustc_data_structures::fx::FxHashSet;
 
-use rustc::middle::region::CodeExtent;
+use rustc::middle::region;
 use rustc::mir::transform::{MirPass, MirSource};
 use rustc::mir::{BasicBlock, Location, Mir, Rvalue, Statement, StatementKind};
 use rustc::mir::visit::{MutVisitor, Visitor, Lookup};
@@ -30,11 +30,11 @@ use rustc::ty::{Ty, RegionKind, TyCtxt};
 pub struct CleanEndRegions;
 
 struct GatherBorrowedRegions {
-    seen_regions: FxHashSet<CodeExtent>,
+    seen_regions: FxHashSet<region::Scope>,
 }
 
 struct DeleteTrivialEndRegions<'a> {
-    seen_regions: &'a FxHashSet<CodeExtent>,
+    seen_regions: &'a FxHashSet<region::Scope>,
 }
 
 impl MirPass for CleanEndRegions {
@@ -84,8 +84,8 @@ impl<'a, 'tcx> MutVisitor<'tcx> for DeleteTrivialEndRegions<'a> {
                        location: Location) {
         let mut delete_it = false;
 
-        if let StatementKind::EndRegion(ref extent) = statement.kind {
-            if !self.seen_regions.contains(extent) {
+        if let StatementKind::EndRegion(ref region_scope) = statement.kind {
+            if !self.seen_regions.contains(region_scope) {
                 delete_it = true;
             }
         }
diff --git a/src/librustc_mir/transform/copy_prop.rs b/src/librustc_mir/transform/copy_prop.rs
index 59b81f7e77c44..ac8ebd306d321 100644
--- a/src/librustc_mir/transform/copy_prop.rs
+++ b/src/librustc_mir/transform/copy_prop.rs
@@ -60,6 +60,7 @@ impl MirPass for CopyPropagation {
                     return
                 }
             }
+            MirSource::GeneratorDrop(_) => (),
         }
 
         // We only run when the MIR optimization level is > 1.
@@ -235,8 +236,7 @@ impl<'tcx> Action<'tcx> {
                 }
 
                 // Replace all uses of the destination local with the source local.
-                let src_lvalue = Lvalue::Local(src_local);
-                def_use_analysis.replace_all_defs_and_uses_with(dest_local, mir, src_lvalue);
+                def_use_analysis.replace_all_defs_and_uses_with(dest_local, mir, src_local);
 
                 // Finally, zap the now-useless assignment instruction.
                 debug!("  Deleting assignment");
diff --git a/src/librustc_mir/transform/elaborate_drops.rs b/src/librustc_mir/transform/elaborate_drops.rs
index 97391452e596d..417083c4ff801 100644
--- a/src/librustc_mir/transform/elaborate_drops.rs
+++ b/src/librustc_mir/transform/elaborate_drops.rs
@@ -96,42 +96,42 @@ fn find_dead_unwinds<'a, 'tcx>(
                            MaybeInitializedLvals::new(tcx, mir, &env),
                            |bd, p| &bd.move_data().move_paths[p]);
     for (bb, bb_data) in mir.basic_blocks().iter_enumerated() {
-        match bb_data.terminator().kind {
+        let location = match bb_data.terminator().kind {
             TerminatorKind::Drop { ref location, unwind: Some(_), .. } |
-            TerminatorKind::DropAndReplace { ref location, unwind: Some(_), .. } => {
-                let mut init_data = InitializationData {
-                    live: flow_inits.sets().on_entry_set_for(bb.index()).to_owned(),
-                    dead: IdxSetBuf::new_empty(env.move_data.move_paths.len()),
-                };
-                debug!("find_dead_unwinds @ {:?}: {:?}; init_data={:?}",
-                       bb, bb_data, init_data.live);
-                for stmt in 0..bb_data.statements.len() {
-                    let loc = Location { block: bb, statement_index: stmt };
-                    init_data.apply_location(tcx, mir, env, loc);
-                }
+            TerminatorKind::DropAndReplace { ref location, unwind: Some(_), .. } => location,
+            _ => continue,
+        };
 
-                let path = match env.move_data.rev_lookup.find(location) {
-                    LookupResult::Exact(e) => e,
-                    LookupResult::Parent(..) => {
-                        debug!("find_dead_unwinds: has parent; skipping");
-                        continue
-                    }
-                };
+        let mut init_data = InitializationData {
+            live: flow_inits.sets().on_entry_set_for(bb.index()).to_owned(),
+            dead: IdxSetBuf::new_empty(env.move_data.move_paths.len()),
+        };
+        debug!("find_dead_unwinds @ {:?}: {:?}; init_data={:?}",
+               bb, bb_data, init_data.live);
+        for stmt in 0..bb_data.statements.len() {
+            let loc = Location { block: bb, statement_index: stmt };
+            init_data.apply_location(tcx, mir, env, loc);
+        }
+
+        let path = match env.move_data.rev_lookup.find(location) {
+            LookupResult::Exact(e) => e,
+            LookupResult::Parent(..) => {
+                debug!("find_dead_unwinds: has parent; skipping");
+                continue
+            }
+        };
 
-                debug!("find_dead_unwinds @ {:?}: path({:?})={:?}", bb, location, path);
+        debug!("find_dead_unwinds @ {:?}: path({:?})={:?}", bb, location, path);
 
-                let mut maybe_live = false;
-                on_all_drop_children_bits(tcx, mir, &env, path, |child| {
-                    let (child_maybe_live, _) = init_data.state(child);
-                    maybe_live |= child_maybe_live;
-                });
+        let mut maybe_live = false;
+        on_all_drop_children_bits(tcx, mir, &env, path, |child| {
+            let (child_maybe_live, _) = init_data.state(child);
+            maybe_live |= child_maybe_live;
+        });
 
-                debug!("find_dead_unwinds @ {:?}: maybe_live={}", bb, maybe_live);
-                if !maybe_live {
-                    dead_unwinds.add(&bb);
-                }
-            }
-            _ => {}
+        debug!("find_dead_unwinds @ {:?}: maybe_live={}", bb, maybe_live);
+        if !maybe_live {
+            dead_unwinds.add(&bb);
         }
     }
 
@@ -314,7 +314,7 @@ impl<'b, 'tcx> ElaborateDropsCtxt<'b, 'tcx> {
         let patch = &mut self.patch;
         debug!("create_drop_flag({:?})", self.mir.span);
         self.drop_flags.entry(index).or_insert_with(|| {
-            patch.new_temp(tcx.types.bool, span)
+            patch.new_internal(tcx.types.bool, span)
         });
     }
 
diff --git a/src/librustc_mir/transform/generator.rs b/src/librustc_mir/transform/generator.rs
new file mode 100644
index 0000000000000..d1e0465f5551c
--- /dev/null
+++ b/src/librustc_mir/transform/generator.rs
@@ -0,0 +1,798 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! This is the implementation of the pass which transforms generators into state machines.
+//!
+//! MIR generation for generators creates a function which has a self argument which
+//! passes by value. This argument is effectively a generator type which only contains upvars and
+//! is only used for this argument inside the MIR for the generator.
+//! It is passed by value to enable upvars to be moved out of it. Drop elaboration runs on that
+//! MIR before this pass and creates drop flags for MIR locals.
+//! It will also drop the generator argument (which only consists of upvars) if any of the upvars
+//! are moved out of. This pass elaborates the drops of upvars / generator argument in the case
+//! that none of the upvars were moved out of. This is because we cannot have any drops of this
+//! generator in the MIR, since it is used to create the drop glue for the generator. We'd get
+//! infinite recursion otherwise.
+//!
+//! This pass creates the implementation for the Generator::resume function and the drop shim
+//! for the generator based on the MIR input. It converts the generator argument from Self to
+//! &mut Self adding derefs in the MIR as needed. It computes the final layout of the generator
+//! struct which looks like this:
+//!     First upvars are stored
+//!     It is followed by the generator state field.
+//!     Then finally the MIR locals which are live across a suspension point are stored.
+//!
+//!     struct Generator {
+//!         upvars...,
+//!         state: u32,
+//!         mir_locals...,
+//!     }
+//!
+//! This pass computes the meaning of the state field and the MIR locals which are live
+//! across a suspension point. There are however two hardcoded generator states:
+//!     0 - Generator have not been resumed yet
+//!     1 - Generator has been poisoned
+//!
+//! It also rewrites `return x` and `yield y` as setting a new generator state and returning
+//! GeneratorState::Complete(x) and GeneratorState::Yielded(y) respectively.
+//! MIR locals which are live across a suspension point are moved to the generator struct
+//! with references to them being updated with references to the generator struct.
+//!
+//! The pass creates two functions which have a switch on the generator state giving
+//! the action to take.
+//!
+//! One of them is the implementation of Generator::resume.
+//! For generators which have already returned it panics.
+//! For generators with state 0 (unresumed) it starts the execution of the generator.
+//! For generators with state 1 (poisoned) it panics.
+//! Otherwise it continues the execution from the last suspension point.
+//!
+//! The other function is the drop glue for the generator.
+//! For generators which have already returned it does nothing.
+//! For generators with state 0 (unresumed) it drops the upvars of the generator.
+//! For generators with state 1 (poisoned) it does nothing.
+//! Otherwise it drops all the values in scope at the last suspension point.
+
+use rustc::hir;
+use rustc::hir::def_id::DefId;
+use rustc::middle::const_val::ConstVal;
+use rustc::mir::*;
+use rustc::mir::transform::{MirPass, MirSource};
+use rustc::mir::visit::{LvalueContext, MutVisitor};
+use rustc::ty::{self, TyCtxt, AdtDef, Ty, GeneratorInterior};
+use rustc::ty::subst::{Kind, Substs};
+use util::dump_mir;
+use util::liveness;
+use rustc_const_math::ConstInt;
+use rustc_data_structures::indexed_vec::Idx;
+use std::collections::HashMap;
+use std::borrow::Cow;
+use std::iter::once;
+use std::mem;
+use transform::simplify;
+use transform::no_landing_pads::no_landing_pads;
+
+pub struct StateTransform;
+
+struct RenameLocalVisitor {
+    from: Local,
+    to: Local,
+}
+
+impl<'tcx> MutVisitor<'tcx> for RenameLocalVisitor {
+    fn visit_local(&mut self,
+                   local: &mut Local,
+                   _: LvalueContext<'tcx>,
+                   _: Location) {
+        if *local == self.from {
+            *local = self.to;
+        }
+    }
+}
+
+struct DerefArgVisitor;
+
+impl<'tcx> MutVisitor<'tcx> for DerefArgVisitor {
+    fn visit_local(&mut self,
+                   local: &mut Local,
+                   _: LvalueContext<'tcx>,
+                   _: Location) {
+        assert_ne!(*local, self_arg());
+    }
+
+    fn visit_lvalue(&mut self,
+                    lvalue: &mut Lvalue<'tcx>,
+                    context: LvalueContext<'tcx>,
+                    location: Location) {
+        if *lvalue == Lvalue::Local(self_arg()) {
+            *lvalue = Lvalue::Projection(Box::new(Projection {
+                base: lvalue.clone(),
+                elem: ProjectionElem::Deref,
+            }));
+        } else {
+            self.super_lvalue(lvalue, context, location);
+        }
+    }
+}
+
+fn self_arg() -> Local {
+    Local::new(1)
+}
+
+struct TransformVisitor<'a, 'tcx: 'a> {
+    tcx: TyCtxt<'a, 'tcx, 'tcx>,
+    state_adt_ref: &'tcx AdtDef,
+    state_substs: &'tcx Substs<'tcx>,
+
+    // The index of the generator state in the generator struct
+    state_field: usize,
+
+    // Mapping from Local to (type of local, generator struct index)
+    remap: HashMap<Local, (Ty<'tcx>, usize)>,
+
+    // The number of generator states. 0 is unresumed, 1 is poisoned. So this is initialized to 2
+    bb_target_count: u32,
+
+    // Map from a (which block to resume execution at, which block to use to drop the generator)
+    // to a generator state
+    bb_targets: HashMap<(BasicBlock, Option<BasicBlock>), u32>,
+
+    // The original RETURN_POINTER local
+    new_ret_local: Local,
+
+    // The block to resume execution when for Return
+    return_block: BasicBlock,
+}
+
+impl<'a, 'tcx> TransformVisitor<'a, 'tcx> {
+    // Make a GeneratorState rvalue
+    fn make_state(&self, idx: usize, val: Operand<'tcx>) -> Rvalue<'tcx> {
+        let adt = AggregateKind::Adt(self.state_adt_ref, idx, self.state_substs, None);
+        Rvalue::Aggregate(box adt, vec![val])
+    }
+
+    // Create a Lvalue referencing a generator struct field
+    fn make_field(&self, idx: usize, ty: Ty<'tcx>) -> Lvalue<'tcx> {
+        let base = Lvalue::Local(self_arg());
+        let field = Projection {
+            base: base,
+            elem: ProjectionElem::Field(Field::new(idx), ty),
+        };
+        Lvalue::Projection(Box::new(field))
+    }
+
+    // Create a statement which changes the generator state
+    fn set_state(&self, state_disc: u32, source_info: SourceInfo) -> Statement<'tcx> {
+        let state = self.make_field(self.state_field, self.tcx.types.u32);
+        let val = Operand::Constant(box Constant {
+            span: source_info.span,
+            ty: self.tcx.types.u32,
+            literal: Literal::Value {
+                value: ConstVal::Integral(ConstInt::U32(state_disc)),
+            },
+        });
+        Statement {
+            source_info,
+            kind: StatementKind::Assign(state, Rvalue::Use(val)),
+        }
+    }
+}
+
+impl<'a, 'tcx> MutVisitor<'tcx> for TransformVisitor<'a, 'tcx> {
+    fn visit_local(&mut self,
+                   local: &mut Local,
+                   _: LvalueContext<'tcx>,
+                   _: Location) {
+        assert_eq!(self.remap.get(local), None);
+    }
+
+    fn visit_lvalue(&mut self,
+                    lvalue: &mut Lvalue<'tcx>,
+                    context: LvalueContext<'tcx>,
+                    location: Location) {
+        if let Lvalue::Local(l) = *lvalue {
+            // Replace an Local in the remap with a generator struct access
+            if let Some(&(ty, idx)) = self.remap.get(&l) {
+                *lvalue = self.make_field(idx, ty);
+            }
+        } else {
+            self.super_lvalue(lvalue, context, location);
+        }
+    }
+
+    fn visit_basic_block_data(&mut self,
+                              block: BasicBlock,
+                              data: &mut BasicBlockData<'tcx>) {
+        // Remove StorageLive and StorageDead statements for remapped locals
+        data.retain_statements(|s| {
+            match s.kind {
+                StatementKind::StorageLive(l) | StatementKind::StorageDead(l) => {
+                    !self.remap.contains_key(&l)
+                }
+                _ => true
+            }
+        });
+
+        let ret_val = match data.terminator().kind {
+            TerminatorKind::Return => Some((1,
+                self.return_block,
+                Operand::Consume(Lvalue::Local(self.new_ret_local)),
+                None)),
+            TerminatorKind::Yield { ref value, resume, drop } => Some((0,
+                resume,
+                value.clone(),
+                drop)),
+            _ => None
+        };
+
+        if let Some((state_idx, resume, v, drop)) = ret_val {
+            let bb_idx = {
+                let bb_targets = &mut self.bb_targets;
+                let bb_target = &mut self.bb_target_count;
+                *bb_targets.entry((resume, drop)).or_insert_with(|| {
+                    let target = *bb_target;
+                    *bb_target = target.checked_add(1).unwrap();
+                    target
+                })
+            };
+            let source_info = data.terminator().source_info;
+            data.statements.push(self.set_state(bb_idx, source_info));
+            data.statements.push(Statement {
+                source_info,
+                kind: StatementKind::Assign(Lvalue::Local(RETURN_POINTER),
+                    self.make_state(state_idx, v)),
+            });
+            data.terminator.as_mut().unwrap().kind = TerminatorKind::Return;
+        }
+
+        self.super_basic_block_data(block, data);
+    }
+}
+
+fn make_generator_state_argument_indirect<'a, 'tcx>(
+                tcx: TyCtxt<'a, 'tcx, 'tcx>,
+                def_id: DefId,
+                mir: &mut Mir<'tcx>) {
+    let gen_ty = mir.local_decls.raw[1].ty;
+
+    let region = ty::ReFree(ty::FreeRegion {
+        scope: def_id,
+        bound_region: ty::BoundRegion::BrEnv,
+    });
+
+    let region = tcx.mk_region(region);
+
+    let ref_gen_ty = tcx.mk_ref(region, ty::TypeAndMut {
+        ty: gen_ty,
+        mutbl: hir::MutMutable
+    });
+
+    // Replace the by value generator argument
+    mir.local_decls.raw[1].ty = ref_gen_ty;
+
+    // Add a deref to accesses of the generator state
+    DerefArgVisitor.visit_mir(mir);
+}
+
+fn replace_result_variable<'tcx>(ret_ty: Ty<'tcx>,
+                            mir: &mut Mir<'tcx>) -> Local {
+    let source_info = SourceInfo {
+        span: mir.span,
+        scope: ARGUMENT_VISIBILITY_SCOPE,
+    };
+
+    let new_ret = LocalDecl {
+        mutability: Mutability::Mut,
+        ty: ret_ty,
+        name: None,
+        source_info,
+        internal: false,
+        is_user_variable: false,
+    };
+    let new_ret_local = Local::new(mir.local_decls.len());
+    mir.local_decls.push(new_ret);
+    mir.local_decls.swap(0, new_ret_local.index());
+
+    RenameLocalVisitor {
+        from: RETURN_POINTER,
+        to: new_ret_local,
+    }.visit_mir(mir);
+
+    new_ret_local
+}
+
+fn locals_live_across_suspend_points<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
+                                               mir: &Mir<'tcx>,
+                                               source: MirSource) -> liveness::LocalSet {
+    let mut set = liveness::LocalSet::new_empty(mir.local_decls.len());
+    let result = liveness::liveness_of_locals(mir);
+    liveness::dump_mir(tcx, "generator_liveness", source, mir, &result);
+
+    for (block, data) in mir.basic_blocks().iter_enumerated() {
+        if let TerminatorKind::Yield { .. } = data.terminator().kind {
+            set.union(&result.outs[block]);
+        }
+    }
+
+    // The generator argument is ignored
+    set.remove(&self_arg());
+
+    set
+}
+
+fn compute_layout<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
+                            source: MirSource,
+                            interior: GeneratorInterior<'tcx>,
+                            mir: &mut Mir<'tcx>)
+    -> (HashMap<Local, (Ty<'tcx>, usize)>, GeneratorLayout<'tcx>)
+{
+    // Use a liveness analysis to compute locals which are live across a suspension point
+    let live_locals = locals_live_across_suspend_points(tcx, mir, source);
+
+    // Erase regions from the types passed in from typeck so we can compare them with
+    // MIR types
+    let allowed = tcx.erase_regions(&interior.as_slice());
+
+    for (local, decl) in mir.local_decls.iter_enumerated() {
+        // Ignore locals which are internal or not live
+        if !live_locals.contains(&local) || decl.internal {
+            continue;
+        }
+
+        // Sanity check that typeck knows about the type of locals which are
+        // live across a suspension point
+        if !allowed.contains(&decl.ty) {
+            span_bug!(mir.span,
+                      "Broken MIR: generator contains type {} in MIR, \
+                       but typeck only knows about {}",
+                      decl.ty,
+                      interior);
+        }
+    }
+
+    let upvar_len = mir.upvar_decls.len();
+    let dummy_local = LocalDecl::new_internal(tcx.mk_nil(), mir.span);
+
+    // Gather live locals and their indices replacing values in mir.local_decls with a dummy
+    // to avoid changing local indices
+    let live_decls = live_locals.iter().map(|local| {
+        let var = mem::replace(&mut mir.local_decls[local], dummy_local.clone());
+        (local, var)
+    });
+
+    // Create a map from local indices to generator struct indices.
+    // These are offset by (upvar_len + 1) because of fields which comes before locals.
+    // We also create a vector of the LocalDecls of these locals.
+    let (remap, vars) = live_decls.enumerate().map(|(idx, (local, var))| {
+        ((local, (var.ty, upvar_len + 1 + idx)), var)
+    }).unzip();
+
+    let layout = GeneratorLayout {
+        fields: vars
+    };
+
+    (remap, layout)
+}
+
+fn insert_entry_point<'tcx>(mir: &mut Mir<'tcx>,
+                            block: BasicBlockData<'tcx>) {
+    mir.basic_blocks_mut().raw.insert(0, block);
+
+    let blocks = mir.basic_blocks_mut().iter_mut();
+
+    for target in blocks.flat_map(|b| b.terminator_mut().successors_mut()) {
+        *target = BasicBlock::new(target.index() + 1);
+    }
+}
+
+fn elaborate_generator_drops<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
+                                       def_id: DefId,
+                                       mir: &mut Mir<'tcx>) {
+    use util::elaborate_drops::{elaborate_drop, Unwind};
+    use util::patch::MirPatch;
+    use shim::DropShimElaborator;
+
+    // Note that `elaborate_drops` only drops the upvars of a generator, and
+    // this is ok because `open_drop` can only be reached within that own
+    // generator's resume function.
+
+    let param_env = tcx.param_env(def_id);
+    let gen = self_arg();
+
+    for block in mir.basic_blocks().indices() {
+        let (target, unwind, source_info) = match mir.basic_blocks()[block].terminator() {
+            &Terminator {
+                source_info,
+                kind: TerminatorKind::Drop {
+                    location: Lvalue::Local(local),
+                    target,
+                    unwind
+                }
+            } if local == gen => (target, unwind, source_info),
+            _ => continue,
+        };
+        let unwind = if let Some(unwind) = unwind {
+            Unwind::To(unwind)
+        } else {
+            Unwind::InCleanup
+        };
+        let patch = {
+            let mut elaborator = DropShimElaborator {
+                mir: &mir,
+                patch: MirPatch::new(mir),
+                tcx,
+                param_env
+            };
+            elaborate_drop(
+                &mut elaborator,
+                source_info,
+                &Lvalue::Local(gen),
+                (),
+                target,
+                unwind,
+                block
+            );
+            elaborator.patch
+        };
+        patch.apply(mir);
+    }
+}
+
+fn create_generator_drop_shim<'a, 'tcx>(
+                tcx: TyCtxt<'a, 'tcx, 'tcx>,
+                transform: &TransformVisitor<'a, 'tcx>,
+                def_id: DefId,
+                source: MirSource,
+                gen_ty: Ty<'tcx>,
+                mir: &Mir<'tcx>,
+                drop_clean: BasicBlock) -> Mir<'tcx> {
+    let mut mir = mir.clone();
+
+    let source_info = SourceInfo {
+        span: mir.span,
+        scope: ARGUMENT_VISIBILITY_SCOPE,
+    };
+
+    let return_block = BasicBlock::new(mir.basic_blocks().len());
+    mir.basic_blocks_mut().push(BasicBlockData {
+        statements: Vec::new(),
+        terminator: Some(Terminator {
+            source_info,
+            kind: TerminatorKind::Return,
+        }),
+        is_cleanup: false,
+    });
+
+    let mut cases: Vec<_> = transform.bb_targets.iter().filter_map(|(&(_, u), &s)| {
+        u.map(|d| (s, d))
+    }).collect();
+
+    cases.insert(0, (0, drop_clean));
+
+    // The poisoned state 1 falls through to the default case which is just to return
+
+    let switch = TerminatorKind::SwitchInt {
+        discr: Operand::Consume(transform.make_field(transform.state_field, tcx.types.u32)),
+        switch_ty: tcx.types.u32,
+        values: Cow::from(cases.iter().map(|&(i, _)| {
+                ConstInt::U32(i)
+            }).collect::<Vec<_>>()),
+        targets: cases.iter().map(|&(_, d)| d).chain(once(return_block)).collect(),
+    };
+
+    insert_entry_point(&mut mir, BasicBlockData {
+        statements: Vec::new(),
+        terminator: Some(Terminator {
+            source_info,
+            kind: switch,
+        }),
+        is_cleanup: false,
+    });
+
+    for block in mir.basic_blocks_mut() {
+        let kind = &mut block.terminator_mut().kind;
+        if let TerminatorKind::GeneratorDrop = *kind {
+            *kind = TerminatorKind::Return;
+        }
+    }
+
+    // Replace the return variable
+    let source_info = SourceInfo {
+        span: mir.span,
+        scope: ARGUMENT_VISIBILITY_SCOPE,
+    };
+
+    mir.return_ty = tcx.mk_nil();
+    mir.local_decls[RETURN_POINTER] = LocalDecl {
+        mutability: Mutability::Mut,
+        ty: tcx.mk_nil(),
+        name: None,
+        source_info,
+        internal: false,
+        is_user_variable: false,
+    };
+
+    make_generator_state_argument_indirect(tcx, def_id, &mut mir);
+
+    // Change the generator argument from &mut to *mut
+    mir.local_decls[self_arg()] = LocalDecl {
+        mutability: Mutability::Mut,
+        ty: tcx.mk_ptr(ty::TypeAndMut {
+            ty: gen_ty,
+            mutbl: hir::Mutability::MutMutable,
+        }),
+        name: None,
+        source_info,
+        internal: false,
+        is_user_variable: false,
+    };
+
+    no_landing_pads(tcx, &mut mir);
+
+    // Make sure we remove dead blocks to remove
+    // unrelated code from the resume part of the function
+    simplify::remove_dead_blocks(&mut mir);
+
+    dump_mir(tcx, None, "generator_drop", &0, source, &mut mir);
+
+    mir
+}
+
+fn insert_panic_on_resume_after_return<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
+                                        mir: &mut Mir<'tcx>) {
+    let assert_block = BasicBlock::new(mir.basic_blocks().len());
+    let term = TerminatorKind::Assert {
+        cond: Operand::Constant(box Constant {
+            span: mir.span,
+            ty: tcx.types.bool,
+            literal: Literal::Value {
+                value: ConstVal::Bool(false),
+            },
+        }),
+        expected: true,
+        msg: AssertMessage::GeneratorResumedAfterReturn,
+        target: assert_block,
+        cleanup: None,
+    };
+
+    let source_info = SourceInfo {
+        span: mir.span,
+        scope: ARGUMENT_VISIBILITY_SCOPE,
+    };
+
+    mir.basic_blocks_mut().push(BasicBlockData {
+        statements: Vec::new(),
+        terminator: Some(Terminator {
+            source_info,
+            kind: term,
+        }),
+        is_cleanup: false,
+    });
+}
+
+fn create_generator_resume_function<'a, 'tcx>(
+        tcx: TyCtxt<'a, 'tcx, 'tcx>,
+        mut transform: TransformVisitor<'a, 'tcx>,
+        def_id: DefId,
+        source: MirSource,
+        mir: &mut Mir<'tcx>) {
+    // Poison the generator when it unwinds
+    for block in mir.basic_blocks_mut() {
+        let source_info = block.terminator().source_info;
+        if let &TerminatorKind::Resume = &block.terminator().kind {
+            block.statements.push(transform.set_state(1, source_info));
+        }
+    }
+
+    let source_info = SourceInfo {
+        span: mir.span,
+        scope: ARGUMENT_VISIBILITY_SCOPE,
+    };
+
+    let poisoned_block = BasicBlock::new(mir.basic_blocks().len());
+
+    let term = TerminatorKind::Assert {
+        cond: Operand::Constant(box Constant {
+            span: mir.span,
+            ty: tcx.types.bool,
+            literal: Literal::Value {
+                value: ConstVal::Bool(false),
+            },
+        }),
+        expected: true,
+        msg: AssertMessage::GeneratorResumedAfterPanic,
+        target: transform.return_block,
+        cleanup: None,
+    };
+
+    mir.basic_blocks_mut().push(BasicBlockData {
+        statements: Vec::new(),
+        terminator: Some(Terminator {
+            source_info,
+            kind: term,
+        }),
+        is_cleanup: false,
+    });
+
+    transform.bb_targets.insert((poisoned_block, None), 1);
+
+    let switch = TerminatorKind::SwitchInt {
+        discr: Operand::Consume(transform.make_field(transform.state_field, tcx.types.u32)),
+        switch_ty: tcx.types.u32,
+        values: Cow::from(transform.bb_targets.values().map(|&i| {
+                ConstInt::U32(i)
+            }).collect::<Vec<_>>()),
+        targets: transform.bb_targets.keys()
+            .map(|&(k, _)| k)
+            .chain(once(transform.return_block))
+            .collect(),
+    };
+
+    insert_entry_point(mir, BasicBlockData {
+        statements: Vec::new(),
+        terminator: Some(Terminator {
+            source_info,
+            kind: switch,
+        }),
+        is_cleanup: false,
+    });
+
+    make_generator_state_argument_indirect(tcx, def_id, mir);
+
+    no_landing_pads(tcx, mir);
+
+    // Make sure we remove dead blocks to remove
+    // unrelated code from the drop part of the function
+    simplify::remove_dead_blocks(mir);
+
+    dump_mir(tcx, None, "generator_resume", &0, source, mir);
+}
+
+fn insert_clean_drop<'a, 'tcx>(mir: &mut Mir<'tcx>) -> BasicBlock {
+    let source_info = SourceInfo {
+        span: mir.span,
+        scope: ARGUMENT_VISIBILITY_SCOPE,
+    };
+
+    let return_block = BasicBlock::new(mir.basic_blocks().len());
+    mir.basic_blocks_mut().push(BasicBlockData {
+        statements: Vec::new(),
+        terminator: Some(Terminator {
+            source_info,
+            kind: TerminatorKind::Return,
+        }),
+        is_cleanup: false,
+    });
+
+    // Create a block to destroy an unresumed generators. This can only destroy upvars.
+    let drop_clean = BasicBlock::new(mir.basic_blocks().len());
+    let term = TerminatorKind::Drop {
+        location: Lvalue::Local(self_arg()),
+        target: return_block,
+        unwind: None,
+    };
+    mir.basic_blocks_mut().push(BasicBlockData {
+        statements: Vec::new(),
+        terminator: Some(Terminator {
+            source_info,
+            kind: term,
+        }),
+        is_cleanup: false,
+    });
+
+    drop_clean
+}
+
+impl MirPass for StateTransform {
+    fn run_pass<'a, 'tcx>(&self,
+                    tcx: TyCtxt<'a, 'tcx, 'tcx>,
+                    source: MirSource,
+                    mir: &mut Mir<'tcx>) {
+        let yield_ty = if let Some(yield_ty) = mir.yield_ty {
+            yield_ty
+        } else {
+            // This only applies to generators
+            return
+        };
+
+        assert!(mir.generator_drop.is_none());
+
+        let node_id = source.item_id();
+        let def_id = tcx.hir.local_def_id(source.item_id());
+        let hir_id = tcx.hir.node_to_hir_id(node_id);
+
+        // Get the interior types which typeck computed
+        let interior = *tcx.typeck_tables_of(def_id).generator_interiors().get(hir_id).unwrap();
+
+        // The first argument is the generator type passed by value
+        let gen_ty = mir.local_decls.raw[1].ty;
+
+        // Compute GeneratorState<yield_ty, return_ty>
+        let state_did = tcx.lang_items.gen_state().unwrap();
+        let state_adt_ref = tcx.adt_def(state_did);
+        let state_substs = tcx.mk_substs([Kind::from(yield_ty),
+            Kind::from(mir.return_ty)].iter());
+        let ret_ty = tcx.mk_adt(state_adt_ref, state_substs);
+
+        // We rename RETURN_POINTER which has type mir.return_ty to new_ret_local
+        // RETURN_POINTER then is a fresh unused local with type ret_ty.
+        let new_ret_local = replace_result_variable(ret_ty, mir);
+
+        // Extract locals which are live across suspension point into `layout`
+        // `remap` gives a mapping from local indices onto generator struct indices
+        let (remap, layout) = compute_layout(tcx, source, interior, mir);
+
+        let state_field = mir.upvar_decls.len();
+
+        let mut bb_targets = HashMap::new();
+
+        // If we jump to the entry point, we should go to the initial 0 generator state.
+        // FIXME: Could this result in the need for destruction for state 0?
+        bb_targets.insert((BasicBlock::new(0), None), 0);
+
+        // Run the transformation which converts Lvalues from Local to generator struct
+        // accesses for locals in `remap`.
+        // It also rewrites `return x` and `yield y` as writing a new generator state and returning
+        // GeneratorState::Complete(x) and GeneratorState::Yielded(y) respectively.
+        let mut transform = TransformVisitor {
+            tcx,
+            state_adt_ref,
+            state_substs,
+            remap,
+            bb_target_count: 2,
+            bb_targets,
+            new_ret_local,
+            state_field,
+
+            // For returns we will resume execution at the next added basic block.
+            // This happens in `insert_panic_on_resume_after_return`
+            return_block: BasicBlock::new(mir.basic_blocks().len()),
+        };
+        transform.visit_mir(mir);
+
+        // Update our MIR struct to reflect the changed we've made
+        mir.return_ty = ret_ty;
+        mir.yield_ty = None;
+        mir.arg_count = 1;
+        mir.spread_arg = None;
+        mir.generator_layout = Some(layout);
+
+        // Panic if we resumed after returning
+        insert_panic_on_resume_after_return(tcx, mir);
+
+        // Insert `drop(generator_struct)` which is used to drop upvars for generators in
+        // the unresumed (0) state.
+        // This is expanded to a drop ladder in `elaborate_generator_drops`.
+        let drop_clean = insert_clean_drop(mir);
+
+        dump_mir(tcx, None, "generator_pre-elab", &0, source, mir);
+
+        // Expand `drop(generator_struct)` to a drop ladder which destroys upvars.
+        // If any upvars are moved out of, drop elaboration will handle upvar destruction.
+        // However we need to also elaborate the code generated by `insert_clean_drop`.
+        elaborate_generator_drops(tcx, def_id, mir);
+
+        dump_mir(tcx, None, "generator_post-transform", &0, source, mir);
+
+        // Create a copy of our MIR and use it to create the drop shim for the generator
+        let drop_shim = create_generator_drop_shim(tcx,
+            &transform,
+            def_id,
+            source,
+            gen_ty,
+            &mir,
+            drop_clean);
+
+        mir.generator_drop = Some(box drop_shim);
+
+        // Create the Generator::resume function
+        create_generator_resume_function(tcx, transform, def_id, source, mir);
+    }
+}
diff --git a/src/librustc_mir/transform/inline.rs b/src/librustc_mir/transform/inline.rs
index 53b46dd2683fc..3f8070fb3aa31 100644
--- a/src/librustc_mir/transform/inline.rs
+++ b/src/librustc_mir/transform/inline.rs
@@ -180,6 +180,10 @@ impl<'a, 'tcx> Inliner<'a, 'tcx> {
             return false;
         }
 
+        // Cannot inline generators which haven't been transformed yet
+        if callee_mir.yield_ty.is_some() {
+            return false;
+        }
 
         let attrs = tcx.get_attrs(callsite.callee);
         let hint = attr::find_inline_attr(None, &attrs[..]);
@@ -585,16 +589,6 @@ impl<'a, 'tcx> Integrator<'a, 'tcx> {
         new
     }
 
-    fn update_local(&self, local: Local) -> Option<Local> {
-        let idx = local.index();
-        if idx < (self.args.len() + 1) {
-            return None;
-        }
-        let idx = idx - (self.args.len() + 1);
-        let local = Local::new(idx);
-        self.local_map.get(local).cloned()
-    }
-
     fn arg_index(&self, arg: Local) -> Option<usize> {
         let idx = arg.index();
         if idx > 0 && idx <= self.args.len() {
@@ -606,32 +600,35 @@ impl<'a, 'tcx> Integrator<'a, 'tcx> {
 }
 
 impl<'a, 'tcx> MutVisitor<'tcx> for Integrator<'a, 'tcx> {
+    fn visit_local(&mut self,
+                   local: &mut Local,
+                   _ctxt: LvalueContext<'tcx>,
+                   _location: Location) {
+        if *local == RETURN_POINTER {
+            match self.destination {
+                Lvalue::Local(l) => *local = l,
+                ref lval => bug!("Return lvalue is {:?}, not local", lval)
+            }
+        }
+        let idx = local.index() - 1;
+        if idx < self.args.len() {
+            match self.args[idx] {
+                Operand::Consume(Lvalue::Local(l)) => *local = l,
+                ref op => bug!("Arg operand `{:?}` is {:?}, not local", idx, op)
+            }
+        }
+        *local = self.local_map[Local::new(idx - self.args.len())];
+    }
+
     fn visit_lvalue(&mut self,
                     lvalue: &mut Lvalue<'tcx>,
                     _ctxt: LvalueContext<'tcx>,
                     _location: Location) {
-        if let Lvalue::Local(ref mut local) = *lvalue {
-            if let Some(l) = self.update_local(*local) {
-                // Temp or Var; update the local reference
-                *local = l;
-                return;
-            }
-        }
-        if let Lvalue::Local(local) = *lvalue {
-            if local == RETURN_POINTER {
-                // Return pointer; update the lvalue itself
-                *lvalue = self.destination.clone();
-            } else if local.index() < (self.args.len() + 1) {
-                // Argument, once again update the the lvalue itself
-                let idx = local.index() - 1;
-                if let Operand::Consume(ref lval) = self.args[idx] {
-                    *lvalue = lval.clone();
-                } else {
-                    bug!("Arg operand `{:?}` is not an Lvalue use.", idx)
-                }
-            }
+        if let Lvalue::Local(RETURN_POINTER) = *lvalue {
+            // Return pointer; update the lvalue itself
+            *lvalue = self.destination.clone();
         } else {
-            self.super_lvalue(lvalue, _ctxt, _location)
+            self.super_lvalue(lvalue, _ctxt, _location);
         }
     }
 
@@ -657,6 +654,8 @@ impl<'a, 'tcx> MutVisitor<'tcx> for Integrator<'a, 'tcx> {
         self.super_terminator_kind(block, kind, loc);
 
         match *kind {
+            TerminatorKind::GeneratorDrop |
+            TerminatorKind::Yield { .. } => bug!(),
             TerminatorKind::Goto { ref mut target} => {
                 *target = self.update_target(*target);
             }
diff --git a/src/librustc_mir/transform/mod.rs b/src/librustc_mir/transform/mod.rs
index d8dffa036621a..e0f2a40ab0732 100644
--- a/src/librustc_mir/transform/mod.rs
+++ b/src/librustc_mir/transform/mod.rs
@@ -40,6 +40,7 @@ pub mod dump_mir;
 pub mod deaggregator;
 pub mod instcombine;
 pub mod copy_prop;
+pub mod generator;
 pub mod inline;
 pub mod nll;
 
diff --git a/src/librustc_mir/transform/no_landing_pads.rs b/src/librustc_mir/transform/no_landing_pads.rs
index 8595663ba18c4..fa6bb644871dc 100644
--- a/src/librustc_mir/transform/no_landing_pads.rs
+++ b/src/librustc_mir/transform/no_landing_pads.rs
@@ -43,6 +43,8 @@ impl<'tcx> MutVisitor<'tcx> for NoLandingPads {
             TerminatorKind::Resume |
             TerminatorKind::Return |
             TerminatorKind::Unreachable |
+            TerminatorKind::GeneratorDrop |
+            TerminatorKind::Yield { .. } |
             TerminatorKind::SwitchInt { .. } => {
                 /* nothing to do */
             },
diff --git a/src/librustc_mir/transform/promote_consts.rs b/src/librustc_mir/transform/promote_consts.rs
index 1665cb2f15eb8..ca6eda5c2d716 100644
--- a/src/librustc_mir/transform/promote_consts.rs
+++ b/src/librustc_mir/transform/promote_consts.rs
@@ -83,52 +83,49 @@ struct TempCollector<'tcx> {
 }
 
 impl<'tcx> Visitor<'tcx> for TempCollector<'tcx> {
-    fn visit_lvalue(&mut self,
-                    lvalue: &Lvalue<'tcx>,
-                    context: LvalueContext<'tcx>,
-                    location: Location) {
-        self.super_lvalue(lvalue, context, location);
-        if let Lvalue::Local(index) = *lvalue {
-            // We're only interested in temporaries
-            if self.mir.local_kind(index) != LocalKind::Temp {
-                return;
-            }
+    fn visit_local(&mut self,
+                   &index: &Local,
+                   context: LvalueContext<'tcx>,
+                   location: Location) {
+        // We're only interested in temporaries
+        if self.mir.local_kind(index) != LocalKind::Temp {
+            return;
+        }
 
-            // Ignore drops, if the temp gets promoted,
-            // then it's constant and thus drop is noop.
-            // Storage live ranges are also irrelevant.
-            if context.is_drop() || context.is_storage_marker() {
-                return;
-            }
+        // Ignore drops, if the temp gets promoted,
+        // then it's constant and thus drop is noop.
+        // Storage live ranges are also irrelevant.
+        if context.is_drop() || context.is_storage_marker() {
+            return;
+        }
 
-            let temp = &mut self.temps[index];
-            if *temp == TempState::Undefined {
-                match context {
-                    LvalueContext::Store |
-                    LvalueContext::Call => {
-                        *temp = TempState::Defined {
-                            location,
-                            uses: 0
-                        };
-                        return;
-                    }
-                    _ => { /* mark as unpromotable below */ }
-                }
-            } else if let TempState::Defined { ref mut uses, .. } = *temp {
-                // We always allow borrows, even mutable ones, as we need
-                // to promote mutable borrows of some ZSTs e.g. `&mut []`.
-                let allowed_use = match context {
-                    LvalueContext::Borrow {..} => true,
-                    _ => context.is_nonmutating_use()
-                };
-                if allowed_use {
-                    *uses += 1;
+        let temp = &mut self.temps[index];
+        if *temp == TempState::Undefined {
+            match context {
+                LvalueContext::Store |
+                LvalueContext::Call => {
+                    *temp = TempState::Defined {
+                        location,
+                        uses: 0
+                    };
                     return;
                 }
-                /* mark as unpromotable below */
+                _ => { /* mark as unpromotable below */ }
             }
-            *temp = TempState::Unpromotable;
+        } else if let TempState::Defined { ref mut uses, .. } = *temp {
+            // We always allow borrows, even mutable ones, as we need
+            // to promote mutable borrows of some ZSTs e.g. `&mut []`.
+            let allowed_use = match context {
+                LvalueContext::Borrow {..} => true,
+                _ => context.is_nonmutating_use()
+            };
+            if allowed_use {
+                *uses += 1;
+                return;
+            }
+            /* mark as unpromotable below */
         }
+        *temp = TempState::Unpromotable;
     }
 
     fn visit_source_info(&mut self, source_info: &SourceInfo) {
@@ -326,16 +323,13 @@ impl<'a, 'tcx> Promoter<'a, 'tcx> {
 
 /// Replaces all temporaries with their promoted counterparts.
 impl<'a, 'tcx> MutVisitor<'tcx> for Promoter<'a, 'tcx> {
-    fn visit_lvalue(&mut self,
-                    lvalue: &mut Lvalue<'tcx>,
-                    context: LvalueContext<'tcx>,
-                    location: Location) {
-        if let Lvalue::Local(ref mut temp) = *lvalue {
-            if self.source.local_kind(*temp) == LocalKind::Temp {
-                *temp = self.promote_temp(*temp);
-            }
+    fn visit_local(&mut self,
+                   local: &mut Local,
+                   _: LvalueContext<'tcx>,
+                   _: Location) {
+        if self.source.local_kind(*local) == LocalKind::Temp {
+            *local = self.promote_temp(*local);
         }
-        self.super_lvalue(lvalue, context, location);
     }
 }
 
@@ -392,6 +386,7 @@ pub fn promote_candidates<'a, 'tcx>(mir: &mut Mir<'tcx>,
                 }).into_iter().collect(),
                 IndexVec::new(),
                 ty,
+                None,
                 initial_locals,
                 0,
                 vec![],
@@ -411,8 +406,8 @@ pub fn promote_candidates<'a, 'tcx>(mir: &mut Mir<'tcx>,
         block.statements.retain(|statement| {
             match statement.kind {
                 StatementKind::Assign(Lvalue::Local(index), _) |
-                StatementKind::StorageLive(Lvalue::Local(index)) |
-                StatementKind::StorageDead(Lvalue::Local(index)) => {
+                StatementKind::StorageLive(index) |
+                StatementKind::StorageDead(index) => {
                     !promoted(index)
                 }
                 _ => true
diff --git a/src/librustc_mir/transform/qualify_consts.rs b/src/librustc_mir/transform/qualify_consts.rs
index ee99bb7d9d520..415421757c5c5 100644
--- a/src/librustc_mir/transform/qualify_consts.rs
+++ b/src/librustc_mir/transform/qualify_consts.rs
@@ -15,6 +15,7 @@
 //! diagnostics as to why a constant rvalue wasn't promoted.
 
 use rustc_data_structures::bitvec::BitVector;
+use rustc_data_structures::indexed_set::IdxSetBuf;
 use rustc_data_structures::indexed_vec::{IndexVec, Idx};
 use rustc::hir;
 use rustc::hir::map as hir_map;
@@ -33,6 +34,7 @@ use syntax::feature_gate::UnstableFeatures;
 use syntax_pos::{Span, DUMMY_SP};
 
 use std::fmt;
+use std::rc::Rc;
 use std::usize;
 
 use super::promote_consts::{self, Candidate, TempState};
@@ -120,13 +122,13 @@ struct Qualifier<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
     return_qualif: Option<Qualif>,
     qualif: Qualif,
     const_fn_arg_vars: BitVector,
+    local_needs_drop: IndexVec<Local, Option<Span>>,
     temp_promotion_state: IndexVec<Local, TempState>,
     promotion_candidates: Vec<Candidate>
 }
 
 impl<'a, 'tcx> Qualifier<'a, 'tcx, 'tcx> {
     fn new(tcx: TyCtxt<'a, 'tcx, 'tcx>,
-           param_env: ty::ParamEnv<'tcx>,
            def_id: DefId,
            mir: &'a Mir<'tcx>,
            mode: Mode)
@@ -141,11 +143,12 @@ impl<'a, 'tcx> Qualifier<'a, 'tcx, 'tcx> {
             mir,
             rpo,
             tcx,
-            param_env,
+            param_env: tcx.param_env(def_id),
             temp_qualif: IndexVec::from_elem(None, &mir.local_decls),
             return_qualif: None,
             qualif: Qualif::empty(),
             const_fn_arg_vars: BitVector::new(mir.local_decls.len()),
+            local_needs_drop: IndexVec::from_elem(None, &mir.local_decls),
             temp_promotion_state: temps,
             promotion_candidates: vec![]
         }
@@ -193,16 +196,26 @@ impl<'a, 'tcx> Qualifier<'a, 'tcx, 'tcx> {
         self.add(original);
     }
 
+    /// Check for NEEDS_DROP (from an ADT or const fn call) and
+    /// error, unless we're in a function.
+    fn always_deny_drop(&self) {
+        self.deny_drop_with_feature_gate_override(false);
+    }
+
     /// Check for NEEDS_DROP (from an ADT or const fn call) and
     /// error, unless we're in a function, or the feature-gate
     /// for globals with destructors is enabled.
     fn deny_drop(&self) {
+        self.deny_drop_with_feature_gate_override(true);
+    }
+
+    fn deny_drop_with_feature_gate_override(&self, allow_gate: bool) {
         if self.mode == Mode::Fn || !self.qualif.intersects(Qualif::NEEDS_DROP) {
             return;
         }
 
         // Static and const fn's allow destructors, but they're feature-gated.
-        let msg = if self.mode != Mode::Const {
+        let msg = if allow_gate && self.mode != Mode::Const {
             // Feature-gate for globals with destructors is enabled.
             if self.tcx.sess.features.borrow().drop_types_in_const {
                 return;
@@ -223,7 +236,7 @@ impl<'a, 'tcx> Qualifier<'a, 'tcx, 'tcx> {
         let mut err =
             struct_span_err!(self.tcx.sess, self.span, E0493, "{}", msg);
 
-        if self.mode != Mode::Const {
+        if allow_gate && self.mode != Mode::Const {
             help!(&mut err,
                   "in Nightly builds, add `#![feature(drop_types_in_const)]` \
                    to the crate attributes to enable");
@@ -231,7 +244,8 @@ impl<'a, 'tcx> Qualifier<'a, 'tcx, 'tcx> {
             self.find_drop_implementation_method_span()
                 .map(|span| err.span_label(span, "destructor defined here"));
 
-            err.span_label(self.span, "constants cannot have destructors");
+            err.span_label(self.span,
+                format!("{}s cannot have destructors", self.mode));
         }
 
         err.emit();
@@ -314,6 +328,15 @@ impl<'a, 'tcx> Qualifier<'a, 'tcx, 'tcx> {
             return;
         }
 
+        // When initializing a local, record whether the *value* being
+        // stored in it needs dropping, which it may not, even if its
+        // type does, e.g. `None::<String>`.
+        if let Lvalue::Local(local) = *dest {
+            if qualif.intersects(Qualif::NEEDS_DROP) {
+                self.local_needs_drop[local] = Some(self.span);
+            }
+        }
+
         match *dest {
             Lvalue::Local(index) if self.mir.local_kind(index) == LocalKind::Temp => {
                 debug!("store to temp {:?}", index);
@@ -346,7 +369,7 @@ impl<'a, 'tcx> Qualifier<'a, 'tcx, 'tcx> {
     }
 
     /// Qualify a whole const, static initializer or const fn.
-    fn qualify_const(&mut self) -> Qualif {
+    fn qualify_const(&mut self) -> (Qualif, Rc<IdxSetBuf<Local>>) {
         debug!("qualifying {} {:?}", self.mode, self.def_id);
 
         let mir = self.mir;
@@ -360,7 +383,6 @@ impl<'a, 'tcx> Qualifier<'a, 'tcx, 'tcx> {
 
             let target = match mir[bb].terminator().kind {
                 TerminatorKind::Goto { target } |
-                // Drops are considered noops.
                 TerminatorKind::Drop { target, .. } |
                 TerminatorKind::Assert { target, .. } |
                 TerminatorKind::Call { destination: Some((_, target)), .. } => {
@@ -369,12 +391,14 @@ impl<'a, 'tcx> Qualifier<'a, 'tcx, 'tcx> {
 
                 // Non-terminating calls cannot produce any value.
                 TerminatorKind::Call { destination: None, .. } => {
-                    return Qualif::empty();
+                    break;
                 }
 
                 TerminatorKind::SwitchInt {..} |
                 TerminatorKind::DropAndReplace { .. } |
                 TerminatorKind::Resume |
+                TerminatorKind::GeneratorDrop |
+                TerminatorKind::Yield { .. } |
                 TerminatorKind::Unreachable => None,
 
                 TerminatorKind::Return => {
@@ -449,7 +473,25 @@ impl<'a, 'tcx> Qualifier<'a, 'tcx, 'tcx> {
                 }
             }
         }
-        self.qualif
+
+        // Collect all the temps we need to promote.
+        let mut promoted_temps = IdxSetBuf::new_empty(self.temp_promotion_state.len());
+
+        for candidate in &self.promotion_candidates {
+            match *candidate {
+                Candidate::Ref(Location { block: bb, statement_index: stmt_idx }) => {
+                    match self.mir[bb].statements[stmt_idx].kind {
+                        StatementKind::Assign(_, Rvalue::Ref(_, _, Lvalue::Local(index))) => {
+                            promoted_temps.add(&index);
+                        }
+                        _ => {}
+                    }
+                }
+                Candidate::ShuffleIndices(_) => {}
+            }
+        }
+
+        (self.qualif, Rc::new(promoted_temps))
     }
 }
 
@@ -457,33 +499,40 @@ impl<'a, 'tcx> Qualifier<'a, 'tcx, 'tcx> {
 /// For functions (constant or not), it also records
 /// candidates for promotion in promotion_candidates.
 impl<'a, 'tcx> Visitor<'tcx> for Qualifier<'a, 'tcx, 'tcx> {
+    fn visit_local(&mut self,
+                   &local: &Local,
+                   _: LvalueContext<'tcx>,
+                   _: Location) {
+        match self.mir.local_kind(local) {
+            LocalKind::ReturnPointer => {
+                self.not_const();
+            }
+            LocalKind::Arg => {
+                self.add(Qualif::FN_ARGUMENT);
+            }
+            LocalKind::Var => {
+                self.add(Qualif::NOT_CONST);
+            }
+            LocalKind::Temp => {
+                if !self.temp_promotion_state[local].is_promotable() {
+                    self.add(Qualif::NOT_PROMOTABLE);
+                }
+
+                if let Some(qualif) = self.temp_qualif[local] {
+                    self.add(qualif);
+                } else {
+                    self.not_const();
+                }
+            }
+        }
+    }
+
     fn visit_lvalue(&mut self,
                     lvalue: &Lvalue<'tcx>,
                     context: LvalueContext<'tcx>,
                     location: Location) {
         match *lvalue {
-            Lvalue::Local(local) => match self.mir.local_kind(local) {
-                LocalKind::ReturnPointer => {
-                    self.not_const();
-                }
-                LocalKind::Arg => {
-                    self.add(Qualif::FN_ARGUMENT);
-                }
-                LocalKind::Var => {
-                    self.add(Qualif::NOT_CONST);
-                }
-                LocalKind::Temp => {
-                    if !self.temp_promotion_state[local].is_promotable() {
-                        self.add(Qualif::NOT_PROMOTABLE);
-                    }
-
-                    if let Some(qualif) = self.temp_qualif[local] {
-                        self.add(qualif);
-                    } else {
-                        self.not_const();
-                    }
-                }
-            },
+            Lvalue::Local(ref local) => self.visit_local(local, context, location),
             Lvalue::Static(ref global) => {
                 self.add(Qualif::STATIC);
 
@@ -493,6 +542,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Qualifier<'a, 'tcx, 'tcx> {
                             span_err!(self.tcx.sess, self.span, E0625,
                                       "thread-local statics cannot be \
                                        accessed at compile-time");
+                            self.add(Qualif::NOT_CONST);
                             return;
                         }
                     }
@@ -558,22 +608,32 @@ impl<'a, 'tcx> Visitor<'tcx> for Qualifier<'a, 'tcx, 'tcx> {
 
     fn visit_operand(&mut self, operand: &Operand<'tcx>, location: Location) {
         match *operand {
-            Operand::Consume(_) => {
+            Operand::Consume(ref lvalue) => {
                 self.nest(|this| {
                     this.super_operand(operand, location);
                     this.try_consume();
                 });
+
+                // Mark the consumed locals to indicate later drops are noops.
+                if let Lvalue::Local(local) = *lvalue {
+                    self.local_needs_drop[local] = None;
+                }
             }
             Operand::Constant(ref constant) => {
-                if let Literal::Item { def_id, substs } = constant.literal {
-                    // Don't peek inside generic (associated) constants.
-                    if substs.types().next().is_some() {
+                if let Literal::Item { def_id, substs: _ } = constant.literal {
+                    // Don't peek inside trait associated constants.
+                    if self.tcx.trait_of_item(def_id).is_some() {
                         self.add_type(constant.ty);
                     } else {
-                        let bits = self.tcx.at(constant.span).mir_const_qualif(def_id);
+                        let (bits, _) = self.tcx.at(constant.span).mir_const_qualif(def_id);
 
                         let qualif = Qualif::from_bits(bits).expect("invalid mir_const_qualif");
                         self.add(qualif);
+
+                        // Just in case the type is more specific than
+                        // the definition, e.g. impl associated const
+                        // with type parameters, take it into account.
+                        self.qualif.restrict(constant.ty, self.tcx, self.param_env);
                     }
 
                     // Let `const fn` transitively have destructors,
@@ -669,13 +729,11 @@ impl<'a, 'tcx> Visitor<'tcx> for Qualifier<'a, 'tcx, 'tcx> {
 
                 // We might have a candidate for promotion.
                 let candidate = Candidate::Ref(location);
-                if self.mode == Mode::Fn || self.mode == Mode::ConstFn {
-                    if !self.qualif.intersects(Qualif::NEVER_PROMOTE) {
-                        // We can only promote direct borrows of temps.
-                        if let Lvalue::Local(local) = *lvalue {
-                            if self.mir.local_kind(local) == LocalKind::Temp {
-                                self.promotion_candidates.push(candidate);
-                            }
+                if !self.qualif.intersects(Qualif::NEVER_PROMOTE) {
+                    // We can only promote direct borrows of temps.
+                    if let Lvalue::Local(local) = *lvalue {
+                        if self.mir.local_kind(local) == LocalKind::Temp {
+                            self.promotion_candidates.push(candidate);
                         }
                     }
                 }
@@ -864,6 +922,30 @@ impl<'a, 'tcx> Visitor<'tcx> for Qualifier<'a, 'tcx, 'tcx> {
                 }
                 self.assign(dest, location);
             }
+        } else if let TerminatorKind::Drop { location: ref lvalue, .. } = *kind {
+            self.super_terminator_kind(bb, kind, location);
+
+            // Deny *any* live drops anywhere other than functions.
+            if self.mode != Mode::Fn {
+                // HACK(eddyb) Emulate a bit of dataflow analysis,
+                // conservatively, that drop elaboration will do.
+                let needs_drop = if let Lvalue::Local(local) = *lvalue {
+                    self.local_needs_drop[local]
+                } else {
+                    None
+                };
+
+                if let Some(span) = needs_drop {
+                    let ty = lvalue.ty(self.mir, self.tcx).to_ty(self.tcx);
+                    self.add_type(ty);
+
+                    // Use the original assignment span to be more precise.
+                    let old_span = self.span;
+                    self.span = span;
+                    self.always_deny_drop();
+                    self.span = old_span;
+                }
+            }
         } else {
             // Qualify any operands inside other terminators.
             self.super_terminator_kind(bb, kind, location);
@@ -942,7 +1024,7 @@ pub fn provide(providers: &mut Providers) {
 
 fn mir_const_qualif<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                               def_id: DefId)
-                              -> u8 {
+                              -> (u8, Rc<IdxSetBuf<Local>>) {
     // NB: This `borrow()` is guaranteed to be valid (i.e., the value
     // cannot yet be stolen), because `mir_validated()`, which steals
     // from `mir_const(), forces this query to execute before
@@ -950,13 +1032,13 @@ fn mir_const_qualif<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
     let mir = &tcx.mir_const(def_id).borrow();
 
     if mir.return_ty.references_error() {
-        return Qualif::NOT_CONST.bits();
+        tcx.sess.delay_span_bug(mir.span, "mir_const_qualif: Mir had errors");
+        return (Qualif::NOT_CONST.bits(), Rc::new(IdxSetBuf::new_empty(0)));
     }
 
-    let param_env = tcx.param_env(def_id);
-
-    let mut qualifier = Qualifier::new(tcx, param_env, def_id, mir, Mode::Const);
-    qualifier.qualify_const().bits()
+    let mut qualifier = Qualifier::new(tcx, def_id, mir, Mode::Const);
+    let (qualif, promoted_temps) = qualifier.qualify_const();
+    (qualif.bits(), promoted_temps)
 }
 
 pub struct QualifyAndPromoteConstants;
@@ -966,8 +1048,15 @@ impl MirPass for QualifyAndPromoteConstants {
                           tcx: TyCtxt<'a, 'tcx, 'tcx>,
                           src: MirSource,
                           mir: &mut Mir<'tcx>) {
+        // There's not really any point in promoting errorful MIR.
+        if mir.return_ty.references_error() {
+            tcx.sess.delay_span_bug(mir.span, "QualifyAndPromoteConstants: Mir had errors");
+            return;
+        }
+
         let id = src.item_id();
         let def_id = tcx.hir.local_def_id(id);
+        let mut const_promoted_temps = None;
         let mode = match src {
             MirSource::Fn(_) => {
                 if tcx.is_const_fn(def_id) {
@@ -976,19 +1065,21 @@ impl MirPass for QualifyAndPromoteConstants {
                     Mode::Fn
                 }
             }
+            MirSource::Const(_) => {
+                const_promoted_temps = Some(tcx.mir_const_qualif(def_id).1);
+                Mode::Const
+            }
             MirSource::Static(_, hir::MutImmutable) => Mode::Static,
             MirSource::Static(_, hir::MutMutable) => Mode::StaticMut,
-            MirSource::Const(_) |
+            MirSource::GeneratorDrop(_) |
             MirSource::Promoted(..) => return
         };
-        let param_env = tcx.param_env(def_id);
 
         if mode == Mode::Fn || mode == Mode::ConstFn {
             // This is ugly because Qualifier holds onto mir,
             // which can't be mutated until its scope ends.
             let (temps, candidates) = {
-                let mut qualifier = Qualifier::new(tcx, param_env,
-                                                   def_id, mir, mode);
+                let mut qualifier = Qualifier::new(tcx, def_id, mir, mode);
                 if mode == Mode::ConstFn {
                     // Enforce a constant-like CFG for `const fn`.
                     qualifier.qualify_const();
@@ -1004,8 +1095,37 @@ impl MirPass for QualifyAndPromoteConstants {
             // Do the actual promotion, now that we know what's viable.
             promote_consts::promote_candidates(mir, tcx, temps, candidates);
         } else {
-            let mut qualifier = Qualifier::new(tcx, param_env, def_id, mir, mode);
-            qualifier.qualify_const();
+            let promoted_temps = if mode == Mode::Const {
+                // Already computed by `mir_const_qualif`.
+                const_promoted_temps.unwrap()
+            } else {
+                Qualifier::new(tcx, def_id, mir, mode).qualify_const().1
+            };
+
+            // In `const` and `static` everything without `StorageDead`
+            // is `'static`, we don't have to create promoted MIR fragments,
+            // just remove `Drop` and `StorageDead` on "promoted" locals.
+            for block in mir.basic_blocks_mut() {
+                block.statements.retain(|statement| {
+                    match statement.kind {
+                        StatementKind::StorageDead(index) => {
+                            !promoted_temps.contains(&index)
+                        }
+                        _ => true
+                    }
+                });
+                let terminator = block.terminator_mut();
+                match terminator.kind {
+                    TerminatorKind::Drop { location: Lvalue::Local(index), target, .. } => {
+                        if promoted_temps.contains(&index) {
+                            terminator.kind = TerminatorKind::Goto {
+                                target,
+                            };
+                        }
+                    }
+                    _ => {}
+                }
+            }
         }
 
         // Statics must be Sync.
diff --git a/src/librustc_mir/transform/simplify.rs b/src/librustc_mir/transform/simplify.rs
index 070250cda4d5d..89828cf375aa7 100644
--- a/src/librustc_mir/transform/simplify.rs
+++ b/src/librustc_mir/transform/simplify.rs
@@ -352,15 +352,11 @@ struct DeclMarker {
 }
 
 impl<'tcx> Visitor<'tcx> for DeclMarker {
-    fn visit_lvalue(&mut self, lval: &Lvalue<'tcx>, ctx: LvalueContext<'tcx>, loc: Location) {
-        if ctx == LvalueContext::StorageLive || ctx == LvalueContext::StorageDead {
-            // ignore these altogether, they get removed along with their otherwise unused decls.
-            return;
+    fn visit_local(&mut self, local: &Local, ctx: LvalueContext<'tcx>, _: Location) {
+        // ignore these altogether, they get removed along with their otherwise unused decls.
+        if ctx != LvalueContext::StorageLive && ctx != LvalueContext::StorageDead {
+            self.locals.insert(local.index());
         }
-        if let Lvalue::Local(ref v) = *lval {
-            self.locals.insert(v.index());
-        }
-        self.super_lvalue(lval, ctx, loc);
     }
 }
 
@@ -373,22 +369,15 @@ impl<'tcx> MutVisitor<'tcx> for LocalUpdater {
         // Remove unnecessary StorageLive and StorageDead annotations.
         data.statements.retain(|stmt| {
             match stmt.kind {
-                StatementKind::StorageLive(ref lval) | StatementKind::StorageDead(ref lval) => {
-                    match *lval {
-                        Lvalue::Local(l) => self.map[l.index()] != !0,
-                        _ => true
-                    }
+                StatementKind::StorageLive(l) | StatementKind::StorageDead(l) => {
+                    self.map[l.index()] != !0
                 }
                 _ => true
             }
         });
         self.super_basic_block_data(block, data);
     }
-    fn visit_lvalue(&mut self, lval: &mut Lvalue<'tcx>, ctx: LvalueContext<'tcx>, loc: Location) {
-        match *lval {
-            Lvalue::Local(ref mut l) => *l = Local::new(self.map[l.index()]),
-            _ => (),
-        };
-        self.super_lvalue(lval, ctx, loc);
+    fn visit_local(&mut self, l: &mut Local, _: LvalueContext<'tcx>, _: Location) {
+        *l = Local::new(self.map[l.index()]);
     }
 }
diff --git a/src/librustc_mir/transform/type_check.rs b/src/librustc_mir/transform/type_check.rs
index 72092042f8d39..d4da14ea96e72 100644
--- a/src/librustc_mir/transform/type_check.rs
+++ b/src/librustc_mir/transform/type_check.rs
@@ -34,7 +34,10 @@ fn mirbug(tcx: TyCtxt, span: Span, msg: &str) {
 macro_rules! span_mirbug {
     ($context:expr, $elem:expr, $($message:tt)*) => ({
         mirbug($context.tcx(), $context.last_span,
-               &format!("broken MIR ({:?}): {}", $elem, format!($($message)*)))
+               &format!("broken MIR in {:?} ({:?}): {}",
+                        $context.body_id,
+                        $elem,
+                        format_args!($($message)*)))
     })
 }
 
@@ -60,6 +63,7 @@ struct TypeVerifier<'a, 'b: 'a, 'gcx: 'b+'tcx, 'tcx: 'b> {
     cx: &'a mut TypeChecker<'b, 'gcx, 'tcx>,
     mir: &'a Mir<'tcx>,
     last_span: Span,
+    body_id: ast::NodeId,
     errors_reported: bool
 }
 
@@ -108,8 +112,9 @@ impl<'a, 'b, 'gcx, 'tcx> Visitor<'tcx> for TypeVerifier<'a, 'b, 'gcx, 'tcx> {
 impl<'a, 'b, 'gcx, 'tcx> TypeVerifier<'a, 'b, 'gcx, 'tcx> {
     fn new(cx: &'a mut TypeChecker<'b, 'gcx, 'tcx>, mir: &'a Mir<'tcx>) -> Self {
         TypeVerifier {
-            cx,
             mir,
+            body_id: cx.body_id,
+            cx,
             last_span: mir.span,
             errors_reported: false
         }
@@ -160,7 +165,7 @@ impl<'a, 'b, 'gcx, 'tcx> TypeVerifier<'a, 'b, 'gcx, 'tcx> {
                            base: LvalueTy<'tcx>,
                            pi: &LvalueElem<'tcx>,
                            lvalue: &Lvalue<'tcx>,
-                           location: Location)
+                           _: Location)
                            -> LvalueTy<'tcx> {
         debug!("sanitize_projection: {:?} {:?} {:?}", base, pi, lvalue);
         let tcx = self.tcx();
@@ -176,9 +181,8 @@ impl<'a, 'b, 'gcx, 'tcx> TypeVerifier<'a, 'b, 'gcx, 'tcx> {
                     })
                 }
             }
-            ProjectionElem::Index(ref i) => {
-                self.visit_operand(i, location);
-                let index_ty = i.ty(self.mir, tcx);
+            ProjectionElem::Index(i) => {
+                let index_ty = Lvalue::Local(i).ty(self.mir, tcx).to_ty(tcx);
                 if index_ty != tcx.types.usize {
                     LvalueTy::Ty {
                         ty: span_mirbug_and_err!(self, i, "index by non-usize {:?}", i)
@@ -297,6 +301,19 @@ impl<'a, 'b, 'gcx, 'tcx> TypeVerifier<'a, 'b, 'gcx, 'tcx> {
                         })
                     }
                 }
+                ty::TyGenerator(def_id, substs, _) => {
+                    // Try upvars first. `field_tys` requires final optimized MIR.
+                    if let Some(ty) = substs.upvar_tys(def_id, tcx).nth(field.index()) {
+                        return Ok(ty);
+                    }
+
+                    return match substs.field_tys(def_id, tcx).nth(field.index()) {
+                        Some(ty) => Ok(ty),
+                        None => Err(FieldAccessError::OutOfRange {
+                            field_count: substs.field_tys(def_id, tcx).count() + 1
+                        })
+                    }
+                }
                 ty::TyTuple(tys, _) => {
                     return match tys.get(field.index()) {
                         Some(&ty) => Ok(ty),
@@ -403,15 +420,8 @@ impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
                                variant_index);
                 };
             }
-            StatementKind::StorageLive(ref lv) |
-            StatementKind::StorageDead(ref lv) => {
-                match *lv {
-                    Lvalue::Local(_) => {}
-                    _ => {
-                        span_mirbug!(self, stmt, "bad lvalue: expected local");
-                    }
-                }
-            }
+            StatementKind::StorageLive(_) |
+            StatementKind::StorageDead(_) |
             StatementKind::InlineAsm { .. } |
             StatementKind::EndRegion(_) |
             StatementKind::Validate(..) |
@@ -428,6 +438,7 @@ impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
             TerminatorKind::Goto { .. } |
             TerminatorKind::Resume |
             TerminatorKind::Return |
+            TerminatorKind::GeneratorDrop |
             TerminatorKind::Unreachable |
             TerminatorKind::Drop { .. } => {
                 // no checks needed for these
@@ -494,6 +505,22 @@ impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
                     }
                 }
             }
+            TerminatorKind::Yield { ref value, .. } => {
+                let value_ty = value.ty(mir, tcx);
+                match mir.yield_ty {
+                    None => span_mirbug!(self, term, "yield in non-generator"),
+                    Some(ty) => {
+                        if let Err(terr) = self.sub_types(value_ty, ty) {
+                            span_mirbug!(self,
+                                term,
+                                "type of yield value is {:?}, but the yield type is {:?}: {:?}",
+                                value_ty,
+                                ty,
+                                terr);
+                        }
+                    }
+                }
+            }
         }
     }
 
@@ -620,6 +647,20 @@ impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
                     span_mirbug!(self, block, "return on cleanup block")
                 }
             }
+            TerminatorKind::GeneratorDrop { .. } => {
+                if is_cleanup {
+                    span_mirbug!(self, block, "generator_drop in cleanup block")
+                }
+            }
+            TerminatorKind::Yield { resume, drop, .. } => {
+                if is_cleanup {
+                    span_mirbug!(self, block, "yield in cleanup block")
+                }
+                self.assert_iscleanup(mir, block, resume, is_cleanup);
+                if let Some(drop) = drop {
+                    self.assert_iscleanup(mir, block, drop, is_cleanup);
+                }
+            }
             TerminatorKind::Unreachable => {}
             TerminatorKind::Drop { target, unwind, .. } |
             TerminatorKind::DropAndReplace { target, unwind, .. } |
diff --git a/src/librustc_mir/util/def_use.rs b/src/librustc_mir/util/def_use.rs
index 8263e149d84e7..bd9fb4bc3cc5f 100644
--- a/src/librustc_mir/util/def_use.rs
+++ b/src/librustc_mir/util/def_use.rs
@@ -10,7 +10,7 @@
 
 //! Def-use analysis.
 
-use rustc::mir::{Local, Location, Lvalue, Mir};
+use rustc::mir::{Local, Location, Mir};
 use rustc::mir::visit::{LvalueContext, MutVisitor, Visitor};
 use rustc_data_structures::indexed_vec::IndexVec;
 use std::marker::PhantomData;
@@ -51,7 +51,7 @@ impl<'tcx> DefUseAnalysis<'tcx> {
     }
 
     fn mutate_defs_and_uses<F>(&self, local: Local, mir: &mut Mir<'tcx>, mut callback: F)
-                               where F: for<'a> FnMut(&'a mut Lvalue<'tcx>,
+                               where F: for<'a> FnMut(&'a mut Local,
                                                       LvalueContext<'tcx>,
                                                       Location) {
         for lvalue_use in &self.info[local].defs_and_uses {
@@ -65,8 +65,8 @@ impl<'tcx> DefUseAnalysis<'tcx> {
     pub fn replace_all_defs_and_uses_with(&self,
                                           local: Local,
                                           mir: &mut Mir<'tcx>,
-                                          new_lvalue: Lvalue<'tcx>) {
-        self.mutate_defs_and_uses(local, mir, |lvalue, _, _| *lvalue = new_lvalue.clone())
+                                          new_local: Local) {
+        self.mutate_defs_and_uses(local, mir, |local, _, _| *local = new_local)
     }
 }
 
@@ -74,30 +74,15 @@ struct DefUseFinder<'tcx> {
     info: IndexVec<Local, Info<'tcx>>,
 }
 
-impl<'tcx> DefUseFinder<'tcx> {
-    fn lvalue_mut_info(&mut self, lvalue: &Lvalue<'tcx>) -> Option<&mut Info<'tcx>> {
-        let info = &mut self.info;
-
-        if let Lvalue::Local(local) = *lvalue {
-            Some(&mut info[local])
-        } else {
-            None
-        }
-    }
-}
-
 impl<'tcx> Visitor<'tcx> for DefUseFinder<'tcx> {
-    fn visit_lvalue(&mut self,
-                    lvalue: &Lvalue<'tcx>,
-                    context: LvalueContext<'tcx>,
-                    location: Location) {
-        if let Some(ref mut info) = self.lvalue_mut_info(lvalue) {
-            info.defs_and_uses.push(Use {
-                context,
-                location,
-            })
-        }
-        self.super_lvalue(lvalue, context, location)
+    fn visit_local(&mut self,
+                   &local: &Local,
+                   context: LvalueContext<'tcx>,
+                   location: Location) {
+        self.info[local].defs_and_uses.push(Use {
+            context,
+            location,
+        });
     }
 }
 
@@ -134,7 +119,7 @@ struct MutateUseVisitor<'tcx, F> {
 impl<'tcx, F> MutateUseVisitor<'tcx, F> {
     fn new(query: Local, callback: F, _: &Mir<'tcx>)
            -> MutateUseVisitor<'tcx, F>
-           where F: for<'a> FnMut(&'a mut Lvalue<'tcx>, LvalueContext<'tcx>, Location) {
+           where F: for<'a> FnMut(&'a mut Local, LvalueContext<'tcx>, Location) {
         MutateUseVisitor {
             query,
             callback,
@@ -144,16 +129,13 @@ impl<'tcx, F> MutateUseVisitor<'tcx, F> {
 }
 
 impl<'tcx, F> MutVisitor<'tcx> for MutateUseVisitor<'tcx, F>
-              where F: for<'a> FnMut(&'a mut Lvalue<'tcx>, LvalueContext<'tcx>, Location) {
-    fn visit_lvalue(&mut self,
-                    lvalue: &mut Lvalue<'tcx>,
+              where F: for<'a> FnMut(&'a mut Local, LvalueContext<'tcx>, Location) {
+    fn visit_local(&mut self,
+                    local: &mut Local,
                     context: LvalueContext<'tcx>,
                     location: Location) {
-        if let Lvalue::Local(local) = *lvalue {
-            if local == self.query {
-                (self.callback)(lvalue, context, location)
-            }
+        if *local == self.query {
+            (self.callback)(local, context, location)
         }
-        self.super_lvalue(lvalue, context, location)
     }
 }
diff --git a/src/librustc_mir/util/elaborate_drops.rs b/src/librustc_mir/util/elaborate_drops.rs
index d8a061f4b1991..f3b121f2eed57 100644
--- a/src/librustc_mir/util/elaborate_drops.rs
+++ b/src/librustc_mir/util/elaborate_drops.rs
@@ -565,7 +565,7 @@ impl<'l, 'b, 'tcx, D> DropCtxt<'l, 'b, 'tcx, D>
     ///    drop(ptr)
     fn drop_loop(&mut self,
                  succ: BasicBlock,
-                 cur: &Lvalue<'tcx>,
+                 cur: Local,
                  length_or_end: &Lvalue<'tcx>,
                  ety: Ty<'tcx>,
                  unwind: Unwind,
@@ -584,20 +584,20 @@ impl<'l, 'b, 'tcx, D> DropCtxt<'l, 'b, 'tcx, D>
 
         let one = self.constant_usize(1);
         let (ptr_next, cur_next) = if ptr_based {
-            (Rvalue::Use(use_(cur)),
-             Rvalue::BinaryOp(BinOp::Offset, use_(cur), one))
+            (Rvalue::Use(use_(&Lvalue::Local(cur))),
+             Rvalue::BinaryOp(BinOp::Offset, use_(&Lvalue::Local(cur)), one))
         } else {
             (Rvalue::Ref(
                  tcx.types.re_erased,
                  BorrowKind::Mut,
-                 self.lvalue.clone().index(use_(cur))),
-             Rvalue::BinaryOp(BinOp::Add, use_(cur), one))
+                 self.lvalue.clone().index(cur)),
+             Rvalue::BinaryOp(BinOp::Add, use_(&Lvalue::Local(cur)), one))
         };
 
         let drop_block = BasicBlockData {
             statements: vec![
                 self.assign(ptr, ptr_next),
-                self.assign(cur, cur_next)
+                self.assign(&Lvalue::Local(cur), cur_next)
             ],
             is_cleanup: unwind.is_cleanup(),
             terminator: Some(Terminator {
@@ -611,7 +611,7 @@ impl<'l, 'b, 'tcx, D> DropCtxt<'l, 'b, 'tcx, D>
         let loop_block = BasicBlockData {
             statements: vec![
                 self.assign(can_go, Rvalue::BinaryOp(BinOp::Eq,
-                                                     use_(cur),
+                                                     use_(&Lvalue::Local(cur)),
                                                      use_(length_or_end)))
             ],
             is_cleanup: unwind.is_cleanup(),
@@ -678,7 +678,7 @@ impl<'l, 'b, 'tcx, D> DropCtxt<'l, 'b, 'tcx, D>
             tcx.types.usize
         };
 
-        let cur = Lvalue::Local(self.new_temp(iter_ty));
+        let cur = self.new_temp(iter_ty);
         let length = Lvalue::Local(self.new_temp(tcx.types.usize));
         let length_or_end = if ptr_based {
             Lvalue::Local(self.new_temp(iter_ty))
@@ -688,7 +688,7 @@ impl<'l, 'b, 'tcx, D> DropCtxt<'l, 'b, 'tcx, D>
 
         let unwind = self.unwind.map(|unwind| {
             self.drop_loop(unwind,
-                           &cur,
+                           cur,
                            &length_or_end,
                            ety,
                            Unwind::InCleanup,
@@ -698,12 +698,13 @@ impl<'l, 'b, 'tcx, D> DropCtxt<'l, 'b, 'tcx, D>
         let succ = self.succ; // FIXME(#6393)
         let loop_block = self.drop_loop(
             succ,
-            &cur,
+            cur,
             &length_or_end,
             ety,
             unwind,
             ptr_based);
 
+        let cur = Lvalue::Local(cur);
         let zero = self.constant_usize(0);
         let mut drop_block_stmts = vec![];
         drop_block_stmts.push(self.assign(&length, Rvalue::Len(self.lvalue.clone())));
@@ -752,7 +753,14 @@ impl<'l, 'b, 'tcx, D> DropCtxt<'l, 'b, 'tcx, D>
     fn open_drop<'a>(&mut self) -> BasicBlock {
         let ty = self.lvalue_ty(self.lvalue);
         match ty.sty {
-            ty::TyClosure(def_id, substs) => {
+            ty::TyClosure(def_id, substs) |
+            // Note that `elaborate_drops` only drops the upvars of a generator,
+            // and this is ok because `open_drop` here can only be reached
+            // within that own generator's resume function.
+            // This should only happen for the self argument on the resume function.
+            // It effetively only contains upvars until the generator transformation runs.
+            // See librustc_mir/transform/generator.rs for more details.
+            ty::TyGenerator(def_id, substs, _) => {
                 let tys : Vec<_> = substs.upvar_tys(def_id, self.tcx()).collect();
                 self.open_drop_for_tuple(&tys)
             }
diff --git a/src/librustc_mir/util/liveness.rs b/src/librustc_mir/util/liveness.rs
new file mode 100644
index 0000000000000..e6d3a82ff9b53
--- /dev/null
+++ b/src/librustc_mir/util/liveness.rs
@@ -0,0 +1,245 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Liveness analysis which computes liveness of MIR local variables at the boundary of basic blocks
+//!
+//! This analysis considers references as being used only at the point of the
+//! borrow. This means that this does not track uses because of references that
+//! already exist:
+//!
+//! ```Rust
+//!     fn foo() {
+//!         x = 0;
+//!         // `x` is live here
+//!         GLOBAL = &x: *const u32;
+//!         // but not here, even while it can be accessed through `GLOBAL`.
+//!         foo();
+//!         x = 1;
+//!         // `x` is live again here, because it is assigned to `OTHER_GLOBAL`
+//!         OTHER_GLOBAL = &x: *const u32;
+//!         // ...
+//!     }
+//! ```
+//!
+//! This means that users of this analysis still have to check whether
+//! pre-existing references can be used to access the value (e.g. at movable
+//! generator yield points, all pre-existing references are invalidated, so this
+//! doesn't matter).
+
+use rustc::mir::*;
+use rustc::mir::visit::{LvalueContext, Visitor};
+use rustc_data_structures::indexed_vec::{IndexVec, Idx};
+use rustc_data_structures::indexed_set::IdxSetBuf;
+use util::pretty::{write_basic_block, dump_enabled, write_mir_intro};
+use rustc::mir::transform::MirSource;
+use rustc::ty::item_path;
+use std::path::{PathBuf, Path};
+use std::fs;
+use rustc::ty::TyCtxt;
+use std::io::{self, Write};
+
+pub type LocalSet = IdxSetBuf<Local>;
+
+#[derive(Eq, PartialEq, Clone)]
+struct BlockInfo {
+    defs: LocalSet,
+    uses: LocalSet,
+}
+
+struct BlockInfoVisitor {
+    pre_defs: LocalSet,
+    defs: LocalSet,
+    uses: LocalSet,
+}
+
+impl<'tcx> Visitor<'tcx> for BlockInfoVisitor {
+    fn visit_local(&mut self,
+                   &local: &Local,
+                   context: LvalueContext<'tcx>,
+                   _: Location) {
+        match context {
+            LvalueContext::Store |
+
+            // We let Call defined the result in both the success and unwind cases.
+            // This may not be right.
+            LvalueContext::Call |
+
+            // Storage live and storage dead aren't proper defines, but we can ignore
+            // values that come before them.
+            LvalueContext::StorageLive |
+            LvalueContext::StorageDead => {
+                self.defs.add(&local);
+            }
+            LvalueContext::Projection(..) |
+
+            // Borrows only consider their local used at the point of the borrow.
+            // This won't affect the results since we use this analysis for generators
+            // and we only care about the result at suspension points. Borrows cannot
+            // cross suspension points so this behavior is unproblematic.
+            LvalueContext::Borrow { .. } |
+
+            LvalueContext::Inspect |
+            LvalueContext::Consume |
+            LvalueContext::Validate |
+
+            // We consider drops to always be uses of locals.
+            // Drop eloboration should be run before this analysis otherwise
+            // the results might be too pessimistic.
+            LvalueContext::Drop => {
+                // Ignore uses which are already defined in this block
+                if !self.pre_defs.contains(&local) {
+                    self.uses.add(&local);
+                }
+            }
+        }
+    }
+}
+
+fn block<'tcx>(b: &BasicBlockData<'tcx>, locals: usize) -> BlockInfo {
+    let mut visitor = BlockInfoVisitor {
+        pre_defs: LocalSet::new_empty(locals),
+        defs: LocalSet::new_empty(locals),
+        uses: LocalSet::new_empty(locals),
+    };
+
+    let dummy_location = Location { block: BasicBlock::new(0), statement_index: 0 };
+
+    for statement in &b.statements {
+        visitor.visit_statement(BasicBlock::new(0), statement, dummy_location);
+        visitor.pre_defs.union(&visitor.defs);
+    }
+    visitor.visit_terminator(BasicBlock::new(0), b.terminator(), dummy_location);
+
+    BlockInfo {
+        defs: visitor.defs,
+        uses: visitor.uses,
+    }
+}
+
+// This gives the result of the liveness analysis at the boundary of basic blocks
+pub struct LivenessResult {
+    pub ins: IndexVec<BasicBlock, LocalSet>,
+    pub outs: IndexVec<BasicBlock, LocalSet>,
+}
+
+pub fn liveness_of_locals<'tcx>(mir: &Mir<'tcx>) -> LivenessResult {
+    let locals = mir.local_decls.len();
+    let def_use: IndexVec<_, _> = mir.basic_blocks().iter().map(|b| {
+        block(b, locals)
+    }).collect();
+
+    let copy = |from: &IndexVec<BasicBlock, LocalSet>, to: &mut IndexVec<BasicBlock, LocalSet>| {
+        for (i, set) in to.iter_enumerated_mut() {
+            set.clone_from(&from[i]);
+        }
+    };
+
+    let mut ins: IndexVec<_, _> = mir.basic_blocks()
+        .indices()
+        .map(|_| LocalSet::new_empty(locals)).collect();
+    let mut outs = ins.clone();
+
+    let mut ins_ = ins.clone();
+    let mut outs_ = outs.clone();
+
+    loop {
+        copy(&ins, &mut ins_);
+        copy(&outs, &mut outs_);
+
+        for b in mir.basic_blocks().indices().rev() {
+            // out = ∪ {ins of successors}
+            outs[b].clear();
+            for &successor in mir.basic_blocks()[b].terminator().successors().into_iter() {
+                outs[b].union(&ins[successor]);
+            }
+
+            // in = use ∪ (out - def)
+            ins[b].clone_from(&outs[b]);
+            ins[b].subtract(&def_use[b].defs);
+            ins[b].union(&def_use[b].uses);
+        }
+
+        if ins_ == ins && outs_ == outs {
+            break;
+        }
+    }
+
+    LivenessResult {
+        ins,
+        outs,
+    }
+}
+
+pub fn dump_mir<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
+                          pass_name: &str,
+                          source: MirSource,
+                          mir: &Mir<'tcx>,
+                          result: &LivenessResult) {
+    if !dump_enabled(tcx, pass_name, source) {
+        return;
+    }
+    let node_path = item_path::with_forced_impl_filename_line(|| { // see notes on #41697 below
+        tcx.item_path_str(tcx.hir.local_def_id(source.item_id()))
+    });
+    dump_matched_mir_node(tcx, pass_name, &node_path,
+                          source, mir, result);
+}
+
+fn dump_matched_mir_node<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
+                                   pass_name: &str,
+                                   node_path: &str,
+                                   source: MirSource,
+                                   mir: &Mir<'tcx>,
+                                   result: &LivenessResult) {
+    let mut file_path = PathBuf::new();
+    if let Some(ref file_dir) = tcx.sess.opts.debugging_opts.dump_mir_dir {
+        let p = Path::new(file_dir);
+        file_path.push(p);
+    };
+    let file_name = format!("rustc.node{}{}-liveness.mir",
+                            source.item_id(), pass_name);
+    file_path.push(&file_name);
+    let _ = fs::File::create(&file_path).and_then(|mut file| {
+        writeln!(file, "// MIR local liveness analysis for `{}`", node_path)?;
+        writeln!(file, "// source = {:?}", source)?;
+        writeln!(file, "// pass_name = {}", pass_name)?;
+        writeln!(file, "")?;
+        write_mir_fn(tcx, source, mir, &mut file, result)?;
+        Ok(())
+    });
+}
+
+pub fn write_mir_fn<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
+                              src: MirSource,
+                              mir: &Mir<'tcx>,
+                              w: &mut Write,
+                              result: &LivenessResult)
+                              -> io::Result<()> {
+    write_mir_intro(tcx, src, mir, w)?;
+    for block in mir.basic_blocks().indices() {
+        let print = |w: &mut Write, prefix, result: &IndexVec<BasicBlock, LocalSet>| {
+            let live: Vec<String> = mir.local_decls.indices()
+                .filter(|i| result[block].contains(i))
+                .map(|i| format!("{:?}", i))
+                .collect();
+            writeln!(w, "{} {{{}}}", prefix, live.join(", "))
+        };
+        print(w, "   ", &result.ins)?;
+        write_basic_block(tcx, block, mir, w)?;
+        print(w, "   ", &result.outs)?;
+        if block.index() + 1 != mir.basic_blocks().len() {
+            writeln!(w, "")?;
+        }
+    }
+
+    writeln!(w, "}}")?;
+    Ok(())
+}
+
diff --git a/src/librustc_mir/util/mod.rs b/src/librustc_mir/util/mod.rs
index f0d837e1362d1..4b6da96824dcd 100644
--- a/src/librustc_mir/util/mod.rs
+++ b/src/librustc_mir/util/mod.rs
@@ -15,6 +15,7 @@ pub mod patch;
 
 mod graphviz;
 mod pretty;
+pub mod liveness;
 
 pub use self::pretty::{dump_enabled, dump_mir, write_mir_pretty};
 pub use self::graphviz::{write_mir_graphviz};
diff --git a/src/librustc_mir/util/patch.rs b/src/librustc_mir/util/patch.rs
index 1af0b6c67f259..66607a9e0986f 100644
--- a/src/librustc_mir/util/patch.rs
+++ b/src/librustc_mir/util/patch.rs
@@ -101,6 +101,13 @@ impl<'tcx> MirPatch<'tcx> {
         Local::new(index as usize)
     }
 
+    pub fn new_internal(&mut self, ty: Ty<'tcx>, span: Span) -> Local {
+        let index = self.next_local;
+        self.next_local += 1;
+        self.new_locals.push(LocalDecl::new_internal(ty, span));
+        Local::new(index as usize)
+    }
+
     pub fn new_block(&mut self, data: BasicBlockData<'tcx>) -> BasicBlock {
         let block = BasicBlock::new(self.patch_map.len());
         debug!("MirPatch: new_block: {:?}: {:?}", block, data);
diff --git a/src/librustc_mir/util/pretty.rs b/src/librustc_mir/util/pretty.rs
index 22a8c4378d4c3..0811783a9e57f 100644
--- a/src/librustc_mir/util/pretty.rs
+++ b/src/librustc_mir/util/pretty.rs
@@ -94,6 +94,7 @@ fn dump_matched_mir_node<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                                    mir: &Mir<'tcx>) {
     let promotion_id = match source {
         MirSource::Promoted(_, id) => format!("-{:?}", id),
+        MirSource::GeneratorDrop(_) => format!("-drop"),
         _ => String::new()
     };
 
@@ -120,6 +121,9 @@ fn dump_matched_mir_node<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
         writeln!(file, "// source = {:?}", source)?;
         writeln!(file, "// pass_name = {}", pass_name)?;
         writeln!(file, "// disambiguator = {}", disambiguator)?;
+        if let Some(ref layout) = mir.generator_layout {
+            writeln!(file, "// generator_layout = {:?}", layout)?;
+        }
         writeln!(file, "")?;
         write_mir_fn(tcx, source, mir, &mut file)?;
         Ok(())
@@ -176,7 +180,7 @@ pub fn write_mir_fn<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 }
 
 /// Write out a human-readable textual representation for the given basic block.
-fn write_basic_block(tcx: TyCtxt,
+pub fn write_basic_block(tcx: TyCtxt,
                      block: BasicBlock,
                      mir: &Mir,
                      w: &mut Write)
@@ -274,7 +278,7 @@ fn write_scope_tree(tcx: TyCtxt,
 
 /// Write out a human-readable textual representation of the MIR's `fn` type and the types of its
 /// local variables (both user-defined bindings and compiler temporaries).
-fn write_mir_intro<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
+pub fn write_mir_intro<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                              src: MirSource,
                              mir: &Mir,
                              w: &mut Write)
@@ -322,28 +326,34 @@ fn write_mir_sig(tcx: TyCtxt, src: MirSource, mir: &Mir, w: &mut Write)
         MirSource::Const(_) => write!(w, "const")?,
         MirSource::Static(_, hir::MutImmutable) => write!(w, "static")?,
         MirSource::Static(_, hir::MutMutable) => write!(w, "static mut")?,
-        MirSource::Promoted(_, i) => write!(w, "{:?} in", i)?
+        MirSource::Promoted(_, i) => write!(w, "{:?} in", i)?,
+        MirSource::GeneratorDrop(_) => write!(w, "drop_glue")?,
     }
 
     item_path::with_forced_impl_filename_line(|| { // see notes on #41697 elsewhere
         write!(w, " {}", tcx.node_path_str(src.item_id()))
     })?;
 
-    if let MirSource::Fn(_) = src {
-        write!(w, "(")?;
-
-        // fn argument types.
-        for (i, arg) in mir.args_iter().enumerate() {
-            if i != 0 {
-                write!(w, ", ")?;
+    match src {
+        MirSource::Fn(_) | MirSource::GeneratorDrop(_) => {
+            write!(w, "(")?;
+
+            // fn argument types.
+            for (i, arg) in mir.args_iter().enumerate() {
+                if i != 0 {
+                    write!(w, ", ")?;
+                }
+                write!(w, "{:?}: {}", Lvalue::Local(arg), mir.local_decls[arg].ty)?;
             }
-            write!(w, "{:?}: {}", Lvalue::Local(arg), mir.local_decls[arg].ty)?;
-        }
 
-        write!(w, ") -> {}", mir.return_ty)
-    } else {
-        assert_eq!(mir.arg_count, 0);
-        write!(w, ": {} =", mir.return_ty)
+            write!(w, ") -> {}", mir.return_ty)
+        }
+        MirSource::Const(..) |
+        MirSource::Static(..) |
+        MirSource::Promoted(..) => {
+            assert_eq!(mir.arg_count, 0);
+            write!(w, ": {} =", mir.return_ty)
+        }
     }
 }
 
diff --git a/src/librustc_passes/consts.rs b/src/librustc_passes/consts.rs
index 763f885b4d005..b4f4f56519121 100644
--- a/src/librustc_passes/consts.rs
+++ b/src/librustc_passes/consts.rs
@@ -87,19 +87,14 @@ impl<'a, 'gcx> CheckCrateVisitor<'a, 'gcx> {
         }
     }
 
-    // Adds the worst effect out of all the values of one type.
-    fn add_type(&mut self, ty: Ty<'gcx>) {
-        if !ty.is_freeze(self.tcx, self.param_env, DUMMY_SP) {
-            self.promotable = false;
-        }
-
-        if ty.needs_drop(self.tcx, self.param_env) {
-            self.promotable = false;
-        }
+    // Returns true iff all the values of the type are promotable.
+    fn type_has_only_promotable_values(&mut self, ty: Ty<'gcx>) -> bool {
+        ty.is_freeze(self.tcx, self.param_env, DUMMY_SP) &&
+        !ty.needs_drop(self.tcx, self.param_env)
     }
 
     fn handle_const_fn_call(&mut self, def_id: DefId, ret_ty: Ty<'gcx>) {
-        self.add_type(ret_ty);
+        self.promotable &= self.type_has_only_promotable_values(ret_ty);
 
         self.promotable &= if let Some(fn_id) = self.tcx.hir.as_local_node_id(def_id) {
             FnLikeNode::from_node(self.tcx.hir.get(fn_id)).map_or(false, |fn_like| {
@@ -148,8 +143,8 @@ impl<'a, 'tcx> Visitor<'tcx> for CheckCrateVisitor<'a, 'tcx> {
 
         let tcx = self.tcx;
         let param_env = self.param_env;
-        let region_maps = self.tcx.region_maps(item_def_id);
-        euv::ExprUseVisitor::new(self, tcx, param_env, &region_maps, self.tables)
+        let region_scope_tree = self.tcx.region_scope_tree(item_def_id);
+        euv::ExprUseVisitor::new(self, tcx, param_env, &region_scope_tree, self.tables)
             .consume_body(body);
 
         self.visit_body(body);
@@ -333,20 +328,30 @@ fn check_expr<'a, 'tcx>(v: &mut CheckCrateVisitor<'a, 'tcx>, e: &hir::Expr, node
             match def {
                 Def::VariantCtor(..) | Def::StructCtor(..) |
                 Def::Fn(..) | Def::Method(..) => {}
-                Def::AssociatedConst(_) => v.add_type(node_ty),
-                Def::Const(did) => {
-                    v.promotable &= if let Some(node_id) = v.tcx.hir.as_local_node_id(did) {
-                        match v.tcx.hir.expect_item(node_id).node {
-                            hir::ItemConst(_, body) => {
+
+                Def::Const(did) |
+                Def::AssociatedConst(did) => {
+                    let promotable = if v.tcx.trait_of_item(did).is_some() {
+                        // Don't peek inside trait associated constants.
+                        false
+                    } else if let Some(node_id) = v.tcx.hir.as_local_node_id(did) {
+                        match v.tcx.hir.maybe_body_owned_by(node_id) {
+                            Some(body) => {
                                 v.visit_nested_body(body);
                                 v.tcx.rvalue_promotable_to_static.borrow()[&body.node_id]
                             }
-                            _ => false
+                            None => false
                         }
                     } else {
                         v.tcx.const_is_rvalue_promotable_to_static(did)
                     };
+
+                    // Just in case the type is more specific than the definition,
+                    // e.g. impl associated const with type parameters, check it.
+                    // Also, trait associated consts are relaxed by this.
+                    v.promotable &= promotable || v.type_has_only_promotable_values(node_ty);
                 }
+
                 _ => {
                     v.promotable = false;
                 }
@@ -435,6 +440,9 @@ fn check_expr<'a, 'tcx>(v: &mut CheckCrateVisitor<'a, 'tcx>, e: &hir::Expr, node
         hir::ExprAgain(_) |
         hir::ExprRet(_) |
 
+        // Generator expressions
+        hir::ExprYield(_) |
+
         // Expressions with side-effects.
         hir::ExprAssign(..) |
         hir::ExprAssignOp(..) |
diff --git a/src/librustc_passes/loops.rs b/src/librustc_passes/loops.rs
index 1b2a07cd1a7b8..c23f28fe2205f 100644
--- a/src/librustc_passes/loops.rs
+++ b/src/librustc_passes/loops.rs
@@ -81,7 +81,7 @@ impl<'a, 'hir> Visitor<'hir> for CheckLoopVisitor<'a, 'hir> {
             hir::ExprLoop(ref b, _, source) => {
                 self.with_context(Loop(LoopKind::Loop(source)), |v| v.visit_block(&b));
             }
-            hir::ExprClosure(.., b, _) => {
+            hir::ExprClosure(.., b, _, _) => {
                 self.with_context(Closure, |v| v.visit_nested_body(b));
             }
             hir::ExprBreak(label, ref opt_expr) => {
diff --git a/src/librustc_passes/mir_stats.rs b/src/librustc_passes/mir_stats.rs
index 9975082c55135..3273d66dd4f51 100644
--- a/src/librustc_passes/mir_stats.rs
+++ b/src/librustc_passes/mir_stats.rs
@@ -120,6 +120,8 @@ impl<'a, 'tcx> mir_visit::Visitor<'tcx> for StatCollector<'a, 'tcx> {
             TerminatorKind::DropAndReplace { .. } => "TerminatorKind::DropAndReplace",
             TerminatorKind::Call { .. } => "TerminatorKind::Call",
             TerminatorKind::Assert { .. } => "TerminatorKind::Assert",
+            TerminatorKind::GeneratorDrop => "TerminatorKind::GeneratorDrop",
+            TerminatorKind::Yield { .. } => "TerminatorKind::Yield",
         }, kind);
         self.super_terminator_kind(block, kind, location);
     }
@@ -131,6 +133,12 @@ impl<'a, 'tcx> mir_visit::Visitor<'tcx> for StatCollector<'a, 'tcx> {
         self.record(match *msg {
             AssertMessage::BoundsCheck { .. } => "AssertMessage::BoundsCheck",
             AssertMessage::Math(..) => "AssertMessage::Math",
+            AssertMessage::GeneratorResumedAfterReturn => {
+                "AssertMessage::GeneratorResumedAfterReturn"
+            }
+            AssertMessage::GeneratorResumedAfterPanic => {
+                "AssertMessage::GeneratorResumedAfterPanic"
+            }
         }, msg);
         self.super_assert_message(msg, location);
     }
@@ -158,6 +166,7 @@ impl<'a, 'tcx> mir_visit::Visitor<'tcx> for StatCollector<'a, 'tcx> {
                     AggregateKind::Tuple => "AggregateKind::Tuple",
                     AggregateKind::Adt(..) => "AggregateKind::Adt",
                     AggregateKind::Closure(..) => "AggregateKind::Closure",
+                    AggregateKind::Generator(..) => "AggregateKind::Generator",
                 }, kind);
 
                 "Rvalue::Aggregate"
diff --git a/src/librustc_privacy/lib.rs b/src/librustc_privacy/lib.rs
index 772b16bbecfba..872a29e7bc0c5 100644
--- a/src/librustc_privacy/lib.rs
+++ b/src/librustc_privacy/lib.rs
@@ -325,8 +325,9 @@ impl<'a, 'tcx> Visitor<'tcx> for EmbargoVisitor<'a, 'tcx> {
         // This code is here instead of in visit_item so that the
         // crate module gets processed as well.
         if self.prev_level.is_some() {
-            if let Some(exports) = self.tcx.export_map.get(&id) {
-                for export in exports {
+            let hir_id = self.tcx.hir.node_to_hir_id(id);
+            if let Some(exports) = self.tcx.module_exports(hir_id) {
+                for export in exports.iter() {
                     if let Some(node_id) = self.tcx.hir.as_local_node_id(export.def.def_id()) {
                         self.update(node_id, Some(AccessLevel::Exported));
                     }
@@ -446,6 +447,7 @@ impl<'b, 'a, 'tcx> TypeVisitor<'tcx> for ReachEverythingInTheInterfaceVisitor<'b
             ty::TyProjection(ref proj) => Some(proj.item_def_id),
             ty::TyFnDef(def_id, ..) |
             ty::TyClosure(def_id, ..) |
+            ty::TyGenerator(def_id, ..) |
             ty::TyAnon(def_id, _) => Some(def_id),
             _ => None
         };
@@ -477,7 +479,7 @@ struct NamePrivacyVisitor<'a, 'tcx: 'a> {
 impl<'a, 'tcx> NamePrivacyVisitor<'a, 'tcx> {
     // Checks that a field is accessible.
     fn check_field(&mut self, span: Span, def: &'tcx ty::AdtDef, field: &'tcx ty::FieldDef) {
-        let ident = Ident { ctxt: span.ctxt.modern(), ..keywords::Invalid.ident() };
+        let ident = Ident { ctxt: span.ctxt().modern(), ..keywords::Invalid.ident() };
         let def_id = self.tcx.adjust_ident(ident, def.did, self.current_item).1;
         if !def.is_enum() && !field.vis.is_accessible_from(def_id, self.tcx) {
             struct_span_err!(self.tcx.sess, span, E0451, "field `{}` of {} `{}` is private",
diff --git a/src/librustc_resolve/lib.rs b/src/librustc_resolve/lib.rs
index a83ac9bb63369..2183c9124e7f4 100644
--- a/src/librustc_resolve/lib.rs
+++ b/src/librustc_resolve/lib.rs
@@ -606,9 +606,7 @@ impl<'tcx> Visitor<'tcx> for UsePlacementFinder {
                     // don't suggest placing a use before the prelude
                     // import or other generated ones
                     if item.span == DUMMY_SP {
-                        let mut span = item.span;
-                        span.hi = span.lo;
-                        self.span = Some(span);
+                        self.span = Some(item.span.with_hi(item.span.lo()));
                         self.found_use = true;
                         return;
                     }
@@ -617,9 +615,7 @@ impl<'tcx> Visitor<'tcx> for UsePlacementFinder {
                 ItemKind::ExternCrate(_) => {}
                 // but place them before the first other item
                 _ => if self.span.map_or(true, |span| item.span < span ) {
-                    let mut span = item.span;
-                    span.hi = span.lo;
-                    self.span = Some(span);
+                    self.span = Some(item.span.with_hi(item.span.lo()));
                 },
             }
         }
@@ -1732,7 +1728,7 @@ impl<'a> Resolver<'a> {
 
     fn resolve_self(&mut self, ctxt: &mut SyntaxContext, module: Module<'a>) -> Module<'a> {
         let mut module = self.get_module(module.normal_ancestor_id);
-        while module.span.ctxt.modern() != *ctxt {
+        while module.span.ctxt().modern() != *ctxt {
             let parent = module.parent.unwrap_or_else(|| self.macro_def_scope(ctxt.remove_mark()));
             module = self.get_module(parent.normal_ancestor_id);
         }
@@ -2659,8 +2655,8 @@ impl<'a> Resolver<'a> {
                 sp = sp.next_point();
                 if let Ok(snippet) = cm.span_to_snippet(sp.to(sp.next_point())) {
                     debug!("snippet {:?}", snippet);
-                    let line_sp = cm.lookup_char_pos(sp.hi).line;
-                    let line_base_sp = cm.lookup_char_pos(base_span.lo).line;
+                    let line_sp = cm.lookup_char_pos(sp.hi()).line;
+                    let line_base_sp = cm.lookup_char_pos(base_span.lo()).line;
                     debug!("{:?} {:?}", line_sp, line_base_sp);
                     if snippet == ":" {
                         err.span_label(base_span,
@@ -3360,7 +3356,7 @@ impl<'a> Resolver<'a> {
         for &(trait_name, binding) in traits.as_ref().unwrap().iter() {
             let module = binding.module().unwrap();
             let mut ident = ident;
-            if ident.ctxt.glob_adjust(module.expansion, binding.span.ctxt.modern()).is_none() {
+            if ident.ctxt.glob_adjust(module.expansion, binding.span.ctxt().modern()).is_none() {
                 continue
             }
             if self.resolve_ident_in_module_unadjusted(module, ident, ns, false, false, module.span)
@@ -3586,7 +3582,7 @@ impl<'a> Resolver<'a> {
                        new_binding: &NameBinding,
                        old_binding: &NameBinding) {
         // Error on the second of two conflicting names
-        if old_binding.span.lo > new_binding.span.lo {
+        if old_binding.span.lo() > new_binding.span.lo() {
             return self.report_conflict(parent, ident, ns, old_binding, new_binding);
         }
 
diff --git a/src/librustc_resolve/macros.rs b/src/librustc_resolve/macros.rs
index f8dc341653ece..9531c8baa0bc1 100644
--- a/src/librustc_resolve/macros.rs
+++ b/src/librustc_resolve/macros.rs
@@ -402,7 +402,8 @@ impl<'a> Resolver<'a> {
         let ast::Path { ref segments, span } = *path;
         let path: Vec<_> = segments.iter().map(|seg| respan(seg.span, seg.identifier)).collect();
         let invocation = self.invocations[&scope];
-        self.current_module = invocation.module.get();
+        let module = invocation.module.get();
+        self.current_module = if module.is_trait() { module.parent.unwrap() } else { module };
 
         if path.len() > 1 {
             if !self.use_extern_macros && self.gated_errors.insert(span) {
diff --git a/src/librustc_resolve/resolve_imports.rs b/src/librustc_resolve/resolve_imports.rs
index 5616971e9d1f5..71bcee56ecc51 100644
--- a/src/librustc_resolve/resolve_imports.rs
+++ b/src/librustc_resolve/resolve_imports.rs
@@ -237,7 +237,7 @@ impl<'a> Resolver<'a> {
             }
             let module = unwrap_or!(directive.imported_module.get(), return Err(Undetermined));
             let (orig_current_module, mut ident) = (self.current_module, ident.modern());
-            match ident.ctxt.glob_adjust(module.expansion, directive.span.ctxt.modern()) {
+            match ident.ctxt.glob_adjust(module.expansion, directive.span.ctxt().modern()) {
                 Some(Some(def)) => self.current_module = self.macro_def_scope(def),
                 Some(None) => {}
                 None => continue,
@@ -398,7 +398,7 @@ impl<'a> Resolver<'a> {
         for directive in module.glob_importers.borrow_mut().iter() {
             let mut ident = ident.modern();
             let scope = match ident.ctxt.reverse_glob_adjust(module.expansion,
-                                                             directive.span.ctxt.modern()) {
+                                                             directive.span.ctxt().modern()) {
                 Some(Some(def)) => self.macro_def_scope(def),
                 Some(None) => directive.parent,
                 None => continue,
@@ -800,7 +800,7 @@ impl<'a, 'b:'a> ImportResolver<'a, 'b> {
         }).collect::<Vec<_>>();
         for ((mut ident, ns), binding) in bindings {
             let scope = match ident.ctxt.reverse_glob_adjust(module.expansion,
-                                                             directive.span.ctxt.modern()) {
+                                                             directive.span.ctxt().modern()) {
                 Some(Some(def)) => self.macro_def_scope(def),
                 Some(None) => self.current_module,
                 None => continue,
diff --git a/src/librustc_save_analysis/lib.rs b/src/librustc_save_analysis/lib.rs
index 9b74df865d747..9ee38dd86c1b5 100644
--- a/src/librustc_save_analysis/lib.rs
+++ b/src/librustc_save_analysis/lib.rs
@@ -91,13 +91,13 @@ impl<'l, 'tcx: 'l> SaveContext<'l, 'tcx> {
         use rls_span::{Row, Column};
 
         let cm = self.tcx.sess.codemap();
-        let start = cm.lookup_char_pos(span.lo);
-        let end = cm.lookup_char_pos(span.hi);
+        let start = cm.lookup_char_pos(span.lo());
+        let end = cm.lookup_char_pos(span.hi());
 
         SpanData {
             file_name: start.file.name.clone().into(),
-            byte_start: span.lo.0,
-            byte_end: span.hi.0,
+            byte_start: span.lo().0,
+            byte_end: span.hi().0,
             line_start: Row::new_one_indexed(start.line as u32),
             line_end: Row::new_one_indexed(end.line as u32),
             column_start: Column::new_one_indexed(start.col.0 as u32 + 1),
@@ -117,7 +117,7 @@ impl<'l, 'tcx: 'l> SaveContext<'l, 'tcx> {
                     continue;
                 }
             };
-            let lo_loc = self.span_utils.sess.codemap().lookup_char_pos(span.lo);
+            let lo_loc = self.span_utils.sess.codemap().lookup_char_pos(span.lo());
             result.push(ExternalCrateData {
                 name: self.tcx.sess.cstore.crate_name(n).to_string(),
                 num: n.as_u32(),
@@ -999,7 +999,7 @@ fn escape(s: String) -> String {
 // Helper function to determine if a span came from a
 // macro expansion or syntax extension.
 fn generated_code(span: Span) -> bool {
-    span.ctxt != NO_EXPANSION || span == DUMMY_SP
+    span.ctxt() != NO_EXPANSION || span == DUMMY_SP
 }
 
 // DefId::index is a newtype and so the JSON serialisation is ugly. Therefore
diff --git a/src/librustc_save_analysis/span_utils.rs b/src/librustc_save_analysis/span_utils.rs
index 36e4d09c963f5..b9d82b8e2512a 100644
--- a/src/librustc_save_analysis/span_utils.rs
+++ b/src/librustc_save_analysis/span_utils.rs
@@ -192,7 +192,7 @@ impl<'a> SpanUtils<'a> {
             prev = next;
         }
         if angle_count != 0 || bracket_count != 0 {
-            let loc = self.sess.codemap().lookup_char_pos(span.lo);
+            let loc = self.sess.codemap().lookup_char_pos(span.lo());
             span_bug!(span,
                       "Mis-counted brackets when breaking path? Parsing '{}' \
                        in {}, line {}",
@@ -319,7 +319,7 @@ impl<'a> SpanUtils<'a> {
         };
 
         //If the span comes from a fake filemap, filter it.
-        if !self.sess.codemap().lookup_char_pos(parent.lo).file.is_real_file() {
+        if !self.sess.codemap().lookup_char_pos(parent.lo()).file.is_real_file() {
             return true;
         }
 
diff --git a/src/librustc_trans/adt.rs b/src/librustc_trans/adt.rs
index d1c1dd7436a5b..11db23732fba3 100644
--- a/src/librustc_trans/adt.rs
+++ b/src/librustc_trans/adt.rs
@@ -77,6 +77,12 @@ pub fn compute_fields<'a, 'tcx>(cx: &CrateContext<'a, 'tcx>, t: Ty<'tcx>,
             if variant_index > 0 { bug!("{} is a closure, which only has one variant", t);}
             substs.upvar_tys(def_id, cx.tcx()).collect()
         },
+        ty::TyGenerator(def_id, substs, _) => {
+            if variant_index > 0 { bug!("{} is a generator, which only has one variant", t);}
+            substs.field_tys(def_id, cx.tcx()).map(|t| {
+                cx.tcx().normalize_associated_type(&t)
+            }).collect()
+        },
         _ => bug!("{} is not a type that can have fields.", t)
     }
 }
diff --git a/src/librustc_trans/attributes.rs b/src/librustc_trans/attributes.rs
index 8863d4ea5ea8a..b6ca1460a7d0a 100644
--- a/src/librustc_trans/attributes.rs
+++ b/src/librustc_trans/attributes.rs
@@ -119,6 +119,8 @@ pub fn from_fn_attrs(ccx: &CrateContext, attrs: &[ast::Attribute], llfn: ValueRe
                 llvm::AttributePlace::ReturnValue(), llfn);
         } else if attr.check_name("unwind") {
             unwind(llfn, true);
+        } else if attr.check_name("rustc_allocator_nounwind") {
+            unwind(llfn, false);
         }
     }
     if !target_features.is_empty() {
diff --git a/src/librustc_trans/back/link.rs b/src/librustc_trans/back/link.rs
index 4e211d83cff3e..4b56376ad9bea 100644
--- a/src/librustc_trans/back/link.rs
+++ b/src/librustc_trans/back/link.rs
@@ -15,7 +15,7 @@ use super::linker::Linker;
 use super::rpath::RPathConfig;
 use super::rpath;
 use metadata::METADATA_FILENAME;
-use rustc::session::config::{self, NoDebugInfo, OutputFilenames, OutputType};
+use rustc::session::config::{self, NoDebugInfo, OutputFilenames, OutputType, PrintRequest};
 use rustc::session::filesearch;
 use rustc::session::search_paths::PathKind;
 use rustc::session::Session;
@@ -647,11 +647,20 @@ fn link_staticlib(sess: &Session,
     ab.build();
 
     if !all_native_libs.is_empty() {
-        sess.note_without_error("link against the following native artifacts when linking against \
-                                 this static library");
-        sess.note_without_error("the order and any duplication can be significant on some \
-                                 platforms, and so may need to be preserved");
+        if sess.opts.prints.contains(&PrintRequest::NativeStaticLibs) {
+            print_native_static_libs(sess, &all_native_libs);
+        } else {
+            // Fallback for backwards compatibility only
+            print_native_static_libs_legacy(sess, &all_native_libs);
+        }
     }
+}
+
+fn print_native_static_libs_legacy(sess: &Session, all_native_libs: &[NativeLibrary]) {
+    sess.note_without_error("link against the following native artifacts when linking against \
+                             this static library");
+    sess.note_without_error("This list will not be printed by default. \
+        Please add --print=native-static-libs if you need this information");
 
     for lib in all_native_libs.iter().filter(|l| relevant_lib(sess, l)) {
         let name = match lib.kind {
@@ -665,6 +674,35 @@ fn link_staticlib(sess: &Session,
     }
 }
 
+fn print_native_static_libs(sess: &Session, all_native_libs: &[NativeLibrary]) {
+    let lib_args: Vec<_> = all_native_libs.iter()
+        .filter(|l| relevant_lib(sess, l))
+        .filter_map(|lib| match lib.kind {
+            NativeLibraryKind::NativeStaticNobundle |
+            NativeLibraryKind::NativeUnknown => {
+                if sess.target.target.options.is_like_msvc {
+                    Some(format!("{}.lib", lib.name))
+                } else {
+                    Some(format!("-l{}", lib.name))
+                }
+            },
+            NativeLibraryKind::NativeFramework => {
+                // ld-only syntax, since there are no frameworks in MSVC
+                Some(format!("-framework {}", lib.name))
+            },
+            // These are included, no need to print them
+            NativeLibraryKind::NativeStatic => None,
+        })
+        .collect();
+    if !lib_args.is_empty() {
+        sess.note_without_error("Link against the following native artifacts when linking \
+                                 against this static library. The order and any duplication \
+                                 can be significant on some platforms.");
+        // Prefix for greppability
+        sess.note_without_error(&format!("native-static-libs: {}", &lib_args.join(" ")));
+    }
+}
+
 // Create a dynamic library or executable
 //
 // This will invoke the system linker/cc to create the resulting file. This
diff --git a/src/librustc_trans/base.rs b/src/librustc_trans/base.rs
index e4b090471d75a..a6c6b0efcfa8c 100644
--- a/src/librustc_trans/base.rs
+++ b/src/librustc_trans/base.rs
@@ -1371,7 +1371,7 @@ fn assert_symbols_are_distinct<'a, 'tcx, I>(tcx: TyCtxt<'a, 'tcx, 'tcx>, trans_i
             // Deterministically select one of the spans for error reporting
             let span = match (span1, span2) {
                 (Some(span1), Some(span2)) => {
-                    Some(if span1.lo.0 > span2.lo.0 {
+                    Some(if span1.lo().0 > span2.lo().0 {
                         span1
                     } else {
                         span2
diff --git a/src/librustc_trans/cabi_powerpc64.rs b/src/librustc_trans/cabi_powerpc64.rs
index 5c695387236fa..fb5472eb6ae1f 100644
--- a/src/librustc_trans/cabi_powerpc64.rs
+++ b/src/librustc_trans/cabi_powerpc64.rs
@@ -14,14 +14,26 @@
 
 use abi::{FnType, ArgType, LayoutExt, Reg, RegKind, Uniform};
 use context::CrateContext;
+use rustc::ty::layout;
 
-fn is_homogeneous_aggregate<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>, arg: &mut ArgType<'tcx>)
+#[derive(Debug, Clone, Copy, PartialEq)]
+enum ABI {
+    ELFv1, // original ABI used for powerpc64 (big-endian)
+    ELFv2, // newer ABI used for powerpc64le
+}
+use self::ABI::*;
+
+fn is_homogeneous_aggregate<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
+                                      arg: &mut ArgType<'tcx>,
+                                      abi: ABI)
                                      -> Option<Uniform> {
     arg.layout.homogeneous_aggregate(ccx).and_then(|unit| {
         let size = arg.layout.size(ccx);
 
-        // Ensure we have at most eight uniquely addressable members.
-        if size > unit.size.checked_mul(8, ccx).unwrap() {
+        // ELFv1 only passes one-member aggregates transparently.
+        // ELFv2 passes up to eight uniquely addressable members.
+        if (abi == ELFv1 && size > unit.size)
+                || size > unit.size.checked_mul(8, ccx).unwrap() {
             return None;
         }
 
@@ -42,21 +54,23 @@ fn is_homogeneous_aggregate<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>, arg: &mut Ar
     })
 }
 
-fn classify_ret_ty<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>, ret: &mut ArgType<'tcx>) {
+fn classify_ret_ty<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>, ret: &mut ArgType<'tcx>, abi: ABI) {
     if !ret.layout.is_aggregate() {
         ret.extend_integer_width_to(64);
         return;
     }
 
-    // The PowerPC64 big endian ABI doesn't return aggregates in registers
-    if ccx.sess().target.target.target_endian == "big" {
+    // The ELFv1 ABI doesn't return aggregates in registers
+    if abi == ELFv1 {
         ret.make_indirect(ccx);
+        return;
     }
 
-    if let Some(uniform) = is_homogeneous_aggregate(ccx, ret) {
+    if let Some(uniform) = is_homogeneous_aggregate(ccx, ret, abi) {
         ret.cast_to(ccx, uniform);
         return;
     }
+
     let size = ret.layout.size(ccx);
     let bits = size.bits();
     if bits <= 128 {
@@ -80,31 +94,55 @@ fn classify_ret_ty<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>, ret: &mut ArgType<'tc
     ret.make_indirect(ccx);
 }
 
-fn classify_arg_ty<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>, arg: &mut ArgType<'tcx>) {
+fn classify_arg_ty<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>, arg: &mut ArgType<'tcx>, abi: ABI) {
     if !arg.layout.is_aggregate() {
         arg.extend_integer_width_to(64);
         return;
     }
 
-    if let Some(uniform) = is_homogeneous_aggregate(ccx, arg) {
+    if let Some(uniform) = is_homogeneous_aggregate(ccx, arg, abi) {
         arg.cast_to(ccx, uniform);
         return;
     }
 
-    let total = arg.layout.size(ccx);
+    let size = arg.layout.size(ccx);
+    let (unit, total) = match abi {
+        ELFv1 => {
+            // In ELFv1, aggregates smaller than a doubleword should appear in
+            // the least-significant bits of the parameter doubleword.  The rest
+            // should be padded at their tail to fill out multiple doublewords.
+            if size.bits() <= 64 {
+                (Reg { kind: RegKind::Integer, size }, size)
+            } else {
+                let align = layout::Align::from_bits(64, 64).unwrap();
+                (Reg::i64(), size.abi_align(align))
+            }
+        },
+        ELFv2 => {
+            // In ELFv2, we can just cast directly.
+            (Reg::i64(), size)
+        },
+    };
+
     arg.cast_to(ccx, Uniform {
-        unit: Reg::i64(),
+        unit,
         total
     });
 }
 
 pub fn compute_abi_info<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>, fty: &mut FnType<'tcx>) {
+    let abi = match ccx.sess().target.target.target_endian.as_str() {
+        "big" => ELFv1,
+        "little" => ELFv2,
+        _ => unimplemented!(),
+    };
+
     if !fty.ret.is_ignore() {
-        classify_ret_ty(ccx, &mut fty.ret);
+        classify_ret_ty(ccx, &mut fty.ret, abi);
     }
 
     for arg in &mut fty.args {
         if arg.is_ignore() { continue; }
-        classify_arg_ty(ccx, arg);
+        classify_arg_ty(ccx, arg, abi);
     }
 }
diff --git a/src/librustc_trans/cabi_x86.rs b/src/librustc_trans/cabi_x86.rs
index 8b024b8c97fa0..49634d6e78ce9 100644
--- a/src/librustc_trans/cabi_x86.rs
+++ b/src/librustc_trans/cabi_x86.rs
@@ -11,12 +11,30 @@
 use abi::{ArgAttribute, FnType, LayoutExt, Reg, RegKind};
 use common::CrateContext;
 
+use rustc::ty::layout::{self, Layout, TyLayout};
+
 #[derive(PartialEq)]
 pub enum Flavor {
     General,
     Fastcall
 }
 
+fn is_single_fp_element<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
+                                  layout: TyLayout<'tcx>) -> bool {
+    match *layout {
+        Layout::Scalar { value: layout::F32, .. } |
+        Layout::Scalar { value: layout::F64, .. } => true,
+        Layout::Univariant { .. } => {
+            if layout.field_count() == 1 {
+                is_single_fp_element(ccx, layout.field(ccx, 0))
+            } else {
+                false
+            }
+        }
+        _ => false
+    }
+}
+
 pub fn compute_abi_info<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
                                   fty: &mut FnType<'tcx>,
                                   flavor: Flavor) {
@@ -33,12 +51,23 @@ pub fn compute_abi_info<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
             if t.options.is_like_osx || t.options.is_like_windows
                 || t.options.is_like_openbsd {
                 let size = fty.ret.layout.size(ccx);
-                match size.bytes() {
-                    1 => fty.ret.cast_to(ccx, Reg::i8()),
-                    2 => fty.ret.cast_to(ccx, Reg::i16()),
-                    4 => fty.ret.cast_to(ccx, Reg::i32()),
-                    8 => fty.ret.cast_to(ccx, Reg::i64()),
-                    _ => fty.ret.make_indirect(ccx)
+
+                // According to Clang, everyone but MSVC returns single-element
+                // float aggregates directly in a floating-point register.
+                if !t.options.is_like_msvc && is_single_fp_element(ccx, fty.ret.layout) {
+                    match size.bytes() {
+                        4 => fty.ret.cast_to(ccx, Reg::f32()),
+                        8 => fty.ret.cast_to(ccx, Reg::f64()),
+                        _ => fty.ret.make_indirect(ccx)
+                    }
+                } else {
+                    match size.bytes() {
+                        1 => fty.ret.cast_to(ccx, Reg::i8()),
+                        2 => fty.ret.cast_to(ccx, Reg::i16()),
+                        4 => fty.ret.cast_to(ccx, Reg::i32()),
+                        8 => fty.ret.cast_to(ccx, Reg::i64()),
+                        _ => fty.ret.make_indirect(ccx)
+                    }
                 }
             } else {
                 fty.ret.make_indirect(ccx);
diff --git a/src/librustc_trans/collector.rs b/src/librustc_trans/collector.rs
index c5de3a4ffb0fd..8b864a7fdcfbb 100644
--- a/src/librustc_trans/collector.rs
+++ b/src/librustc_trans/collector.rs
@@ -629,6 +629,8 @@ impl<'a, 'tcx> MirVisitor<'tcx> for MirNeighborCollector<'a, 'tcx> {
             mir::TerminatorKind::Return |
             mir::TerminatorKind::Unreachable |
             mir::TerminatorKind::Assert { .. } => {}
+            mir::TerminatorKind::GeneratorDrop |
+            mir::TerminatorKind::Yield { .. } => bug!(),
         }
 
         self.super_terminator_kind(block, kind, location);
diff --git a/src/librustc_trans/common.rs b/src/librustc_trans/common.rs
index 09aa3d2335a6a..261792735dcab 100644
--- a/src/librustc_trans/common.rs
+++ b/src/librustc_trans/common.rs
@@ -28,12 +28,13 @@ use type_::Type;
 use value::Value;
 use rustc::ty::{self, Ty, TyCtxt};
 use rustc::ty::layout::{Layout, LayoutTyper};
-use rustc::ty::subst::{Subst, Substs};
+use rustc::ty::subst::{Kind, Subst, Substs};
 use rustc::hir;
 
 use libc::{c_uint, c_char};
 use std::iter;
 
+use syntax::abi::Abi;
 use syntax::attr;
 use syntax::symbol::InternedString;
 use syntax_pos::Span;
@@ -91,6 +92,16 @@ pub fn type_pair_fields<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>, ty: Ty<'tcx>)
                 }
             }))
         }
+        ty::TyGenerator(def_id, substs, _) => {
+            let mut tys = substs.field_tys(def_id, ccx.tcx());
+            tys.next().and_then(|first_ty| tys.next().and_then(|second_ty| {
+                if tys.next().is_some() {
+                    None
+                } else {
+                    Some([first_ty, second_ty])
+                }
+            }))
+        }
         ty::TyTuple(tys, _) => {
             if tys.len() != 2 {
                 return None;
@@ -511,6 +522,28 @@ pub fn ty_fn_sig<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
                 sig.abi
             ))
         }
+        ty::TyGenerator(def_id, substs, _) => {
+            let tcx = ccx.tcx();
+            let sig = tcx.generator_sig(def_id).unwrap().subst(tcx, substs.substs);
+
+            let env_region = ty::ReLateBound(ty::DebruijnIndex::new(1), ty::BrEnv);
+            let env_ty = tcx.mk_mut_ref(tcx.mk_region(env_region), ty);
+
+            sig.map_bound(|sig| {
+                let state_did = tcx.lang_items.gen_state().unwrap();
+                let state_adt_ref = tcx.adt_def(state_did);
+                let state_substs = tcx.mk_substs([Kind::from(sig.yield_ty),
+                    Kind::from(sig.return_ty)].iter());
+                let ret_ty = tcx.mk_adt(state_adt_ref, state_substs);
+
+                tcx.mk_fn_sig(iter::once(env_ty),
+                    ret_ty,
+                    false,
+                    hir::Unsafety::Normal,
+                    Abi::Rust
+                )
+            })
+        }
         _ => bug!("unexpected type {:?} to ty_fn_sig", ty)
     }
 }
diff --git a/src/librustc_trans/debuginfo/metadata.rs b/src/librustc_trans/debuginfo/metadata.rs
index 9aba075a20cdb..bcc6aca6149bd 100644
--- a/src/librustc_trans/debuginfo/metadata.rs
+++ b/src/librustc_trans/debuginfo/metadata.rs
@@ -580,6 +580,16 @@ pub fn type_metadata<'a, 'tcx>(cx: &CrateContext<'a, 'tcx>,
                                    unique_type_id,
                                    usage_site_span).finalize(cx)
         }
+        ty::TyGenerator(def_id, substs, _) => {
+            let upvar_tys : Vec<_> = substs.field_tys(def_id, cx.tcx()).map(|t| {
+                cx.tcx().normalize_associated_type(&t)
+            }).collect();
+            prepare_tuple_metadata(cx,
+                                   t,
+                                   &upvar_tys,
+                                   unique_type_id,
+                                   usage_site_span).finalize(cx)
+        }
         ty::TyAdt(def, ..) => match def.adt_kind() {
             AdtKind::Struct => {
                 prepare_struct_metadata(cx,
diff --git a/src/librustc_trans/debuginfo/type_names.rs b/src/librustc_trans/debuginfo/type_names.rs
index 8cb2c2809f4f3..5dd1c15fd2d6e 100644
--- a/src/librustc_trans/debuginfo/type_names.rs
+++ b/src/librustc_trans/debuginfo/type_names.rs
@@ -165,6 +165,9 @@ pub fn push_debuginfo_type_name<'a, 'tcx>(cx: &CrateContext<'a, 'tcx>,
         ty::TyClosure(..) => {
             output.push_str("closure");
         }
+        ty::TyGenerator(..) => {
+            output.push_str("generator");
+        }
         ty::TyError |
         ty::TyInfer(_) |
         ty::TyProjection(..) |
diff --git a/src/librustc_trans/debuginfo/utils.rs b/src/librustc_trans/debuginfo/utils.rs
index 6df509f34a472..7529139c05aac 100644
--- a/src/librustc_trans/debuginfo/utils.rs
+++ b/src/librustc_trans/debuginfo/utils.rs
@@ -49,7 +49,7 @@ pub fn create_DIArray(builder: DIBuilderRef, arr: &[DIDescriptor]) -> DIArray {
 
 /// Return syntax_pos::Loc corresponding to the beginning of the span
 pub fn span_start(cx: &CrateContext, span: Span) -> syntax_pos::Loc {
-    cx.sess().codemap().lookup_char_pos(span.lo)
+    cx.sess().codemap().lookup_char_pos(span.lo())
 }
 
 pub fn size_and_align_of(cx: &CrateContext, llvm_type: Type) -> (u64, u32) {
diff --git a/src/librustc_trans/intrinsic.rs b/src/librustc_trans/intrinsic.rs
index 033ef988571dd..9a3c8a5079a2f 100644
--- a/src/librustc_trans/intrinsic.rs
+++ b/src/librustc_trans/intrinsic.rs
@@ -383,6 +383,18 @@ pub fn trans_intrinsic_call<'a, 'tcx>(bcx: &Builder<'a, 'tcx>,
                 _ => C_null(llret_ty)
             }
         }
+
+        "align_offset" => {
+            // `ptr as usize`
+            let ptr_val = bcx.ptrtoint(llargs[0], bcx.ccx.int_type());
+            // `ptr_val % align`
+            let offset = bcx.urem(ptr_val, llargs[1]);
+            let zero = C_null(bcx.ccx.int_type());
+            // `offset == 0`
+            let is_zero = bcx.icmp(llvm::IntPredicate::IntEQ, offset, zero);
+            // `if offset == 0 { 0 } else { offset - align }`
+            bcx.select(is_zero, zero, bcx.sub(offset, llargs[1]))
+        }
         name if name.starts_with("simd_") => {
             generic_simd_intrinsic(bcx, name,
                                    callee_ty,
diff --git a/src/librustc_trans/mir/analyze.rs b/src/librustc_trans/mir/analyze.rs
index 598af1cda91d4..95b76d32bf848 100644
--- a/src/librustc_trans/mir/analyze.rs
+++ b/src/librustc_trans/mir/analyze.rs
@@ -134,60 +134,61 @@ impl<'mir, 'a, 'tcx> Visitor<'tcx> for LocalAnalyzer<'mir, 'a, 'tcx> {
                     location: Location) {
         debug!("visit_lvalue(lvalue={:?}, context={:?})", lvalue, context);
 
-        // Allow uses of projections of immediate pair fields.
         if let mir::Lvalue::Projection(ref proj) = *lvalue {
-            if let mir::Lvalue::Local(_) = proj.base {
-                let ty = proj.base.ty(self.cx.mir, self.cx.ccx.tcx());
-
-                let ty = self.cx.monomorphize(&ty.to_ty(self.cx.ccx.tcx()));
-                if common::type_is_imm_pair(self.cx.ccx, ty) {
+            // Allow uses of projections of immediate pair fields.
+            if let LvalueContext::Consume = context {
+                if let mir::Lvalue::Local(_) = proj.base {
                     if let mir::ProjectionElem::Field(..) = proj.elem {
-                        if let LvalueContext::Consume = context {
+                        let ty = proj.base.ty(self.cx.mir, self.cx.ccx.tcx());
+
+                        let ty = self.cx.monomorphize(&ty.to_ty(self.cx.ccx.tcx()));
+                        if common::type_is_imm_pair(self.cx.ccx, ty) {
                             return;
                         }
                     }
                 }
             }
-        }
 
-        if let mir::Lvalue::Local(index) = *lvalue {
-            match context {
-                LvalueContext::Call => {
-                    self.mark_assigned(index);
-                }
+            // A deref projection only reads the pointer, never needs the lvalue.
+            if let mir::ProjectionElem::Deref = proj.elem {
+                return self.visit_lvalue(&proj.base, LvalueContext::Consume, location);
+            }
+        }
 
-                LvalueContext::StorageLive |
-                LvalueContext::StorageDead |
-                LvalueContext::Validate |
-                LvalueContext::Inspect |
-                LvalueContext::Consume => {}
+        self.super_lvalue(lvalue, context, location);
+    }
 
-                LvalueContext::Store |
-                LvalueContext::Borrow { .. } |
-                LvalueContext::Projection(..) => {
-                    self.mark_as_lvalue(index);
-                }
+    fn visit_local(&mut self,
+                   &index: &mir::Local,
+                   context: LvalueContext<'tcx>,
+                   _: Location) {
+        match context {
+            LvalueContext::Call => {
+                self.mark_assigned(index);
+            }
 
-                LvalueContext::Drop => {
-                    let ty = lvalue.ty(self.cx.mir, self.cx.ccx.tcx());
-                    let ty = self.cx.monomorphize(&ty.to_ty(self.cx.ccx.tcx()));
+            LvalueContext::StorageLive |
+            LvalueContext::StorageDead |
+            LvalueContext::Validate |
+            LvalueContext::Inspect |
+            LvalueContext::Consume => {}
 
-                    // Only need the lvalue if we're actually dropping it.
-                    if self.cx.ccx.shared().type_needs_drop(ty) {
-                        self.mark_as_lvalue(index);
-                    }
-                }
+            LvalueContext::Store |
+            LvalueContext::Borrow { .. } |
+            LvalueContext::Projection(..) => {
+                self.mark_as_lvalue(index);
             }
-        }
 
-        // A deref projection only reads the pointer, never needs the lvalue.
-        if let mir::Lvalue::Projection(ref proj) = *lvalue {
-            if let mir::ProjectionElem::Deref = proj.elem {
-                return self.visit_lvalue(&proj.base, LvalueContext::Consume, location);
+            LvalueContext::Drop => {
+                let ty = mir::Lvalue::Local(index).ty(self.cx.mir, self.cx.ccx.tcx());
+                let ty = self.cx.monomorphize(&ty.to_ty(self.cx.ccx.tcx()));
+
+                // Only need the lvalue if we're actually dropping it.
+                if self.cx.ccx.shared().type_needs_drop(ty) {
+                    self.mark_as_lvalue(index);
+                }
             }
         }
-
-        self.super_lvalue(lvalue, context, location);
     }
 }
 
@@ -216,8 +217,10 @@ pub fn cleanup_kinds<'a, 'tcx>(mir: &mir::Mir<'tcx>) -> IndexVec<mir::BasicBlock
                 TerminatorKind::Goto { .. } |
                 TerminatorKind::Resume |
                 TerminatorKind::Return |
+                TerminatorKind::GeneratorDrop |
                 TerminatorKind::Unreachable |
-                TerminatorKind::SwitchInt { .. } => {
+                TerminatorKind::SwitchInt { .. } |
+                TerminatorKind::Yield { .. }  => {
                     /* nothing to do */
                 }
                 TerminatorKind::Call { cleanup: unwind, .. } |
diff --git a/src/librustc_trans/mir/block.rs b/src/librustc_trans/mir/block.rs
index 28fe1044e7454..bba3b1fa5baee 100644
--- a/src/librustc_trans/mir/block.rs
+++ b/src/librustc_trans/mir/block.rs
@@ -330,7 +330,7 @@ impl<'a, 'tcx> MirContext<'a, 'tcx> {
                 self.set_debug_loc(&bcx, terminator.source_info);
 
                 // Get the location information.
-                let loc = bcx.sess().codemap().lookup_char_pos(span.lo);
+                let loc = bcx.sess().codemap().lookup_char_pos(span.lo());
                 let filename = Symbol::intern(&loc.file.name).as_str();
                 let filename = C_str_slice(bcx.ccx, filename);
                 let line = C_u32(bcx.ccx, loc.line as u32);
@@ -374,6 +374,27 @@ impl<'a, 'tcx> MirContext<'a, 'tcx> {
                          vec![msg_file_line_col],
                          Some(ErrKind::Math(err.clone())))
                     }
+                    mir::AssertMessage::GeneratorResumedAfterReturn |
+                    mir::AssertMessage::GeneratorResumedAfterPanic => {
+                        let str = if let mir::AssertMessage::GeneratorResumedAfterReturn = *msg {
+                            "generator resumed after completion"
+                        } else {
+                            "generator resumed after panicking"
+                        };
+                        let msg_str = Symbol::intern(str).as_str();
+                        let msg_str = C_str_slice(bcx.ccx, msg_str);
+                        let msg_file_line = C_struct(bcx.ccx,
+                                                     &[msg_str, filename, line],
+                                                     false);
+                        let align = llalign_of_min(bcx.ccx, common::val_ty(msg_file_line));
+                        let msg_file_line = consts::addr_of(bcx.ccx,
+                                                            msg_file_line,
+                                                            align,
+                                                            "panic_loc");
+                        (lang_items::PanicFnLangItem,
+                         vec![msg_file_line],
+                         None)
+                    }
                 };
 
                 // If we know we always panic, and the error message
@@ -557,6 +578,8 @@ impl<'a, 'tcx> MirContext<'a, 'tcx> {
                         destination.as_ref().map(|&(_, target)| (ret_dest, sig.output(), target)),
                         cleanup);
             }
+            mir::TerminatorKind::GeneratorDrop |
+            mir::TerminatorKind::Yield { .. } => bug!("generator ops in trans"),
         }
     }
 
diff --git a/src/librustc_trans/mir/constant.rs b/src/librustc_trans/mir/constant.rs
index 293e6462de279..9987c9c33102d 100644
--- a/src/librustc_trans/mir/constant.rs
+++ b/src/librustc_trans/mir/constant.rs
@@ -336,6 +336,9 @@ impl<'a, 'tcx> MirConstContext<'a, 'tcx> {
                             mir::AssertMessage::Math(ref err) => {
                                 ErrKind::Math(err.clone())
                             }
+                            mir::AssertMessage::GeneratorResumedAfterReturn |
+                            mir::AssertMessage::GeneratorResumedAfterPanic =>
+                                span_bug!(span, "{:?} should not appear in constants?", msg),
                         };
 
                         let err = ConstEvalErr { span: span, kind: err };
@@ -468,7 +471,8 @@ impl<'a, 'tcx> MirConstContext<'a, 'tcx> {
                         };
                         (Base::Value(llprojected), llextra)
                     }
-                    mir::ProjectionElem::Index(ref index) => {
+                    mir::ProjectionElem::Index(index) => {
+                        let index = &mir::Operand::Consume(mir::Lvalue::Local(index));
                         let llindex = self.const_operand(index, span)?.llval;
 
                         let iv = if let Some(iv) = common::const_to_opt_u128(llindex, false) {
@@ -579,6 +583,7 @@ impl<'a, 'tcx> MirConstContext<'a, 'tcx> {
                     }
                     mir::AggregateKind::Adt(..) |
                     mir::AggregateKind::Closure(..) |
+                    mir::AggregateKind::Generator(..) |
                     mir::AggregateKind::Tuple => {
                         Const::new(trans_const(self.ccx, dest_ty, kind, &fields), dest_ty)
                     }
diff --git a/src/librustc_trans/mir/lvalue.rs b/src/librustc_trans/mir/lvalue.rs
index 89c76ccdd27c2..8155303b0d3fc 100644
--- a/src/librustc_trans/mir/lvalue.rs
+++ b/src/librustc_trans/mir/lvalue.rs
@@ -333,7 +333,8 @@ impl<'a, 'tcx> MirContext<'a, 'tcx> {
                         };
                         (tr_base.trans_field_ptr(bcx, field.index()), llextra)
                     }
-                    mir::ProjectionElem::Index(ref index) => {
+                    mir::ProjectionElem::Index(index) => {
+                        let index = &mir::Operand::Consume(mir::Lvalue::Local(index));
                         let index = self.trans_operand(bcx, index);
                         let llindex = self.prepare_index(bcx, index.immediate());
                         ((tr_base.project_index(bcx, llindex), align), ptr::null_mut())
diff --git a/src/librustc_trans/mir/mod.rs b/src/librustc_trans/mir/mod.rs
index a67fa070324c3..5206ad74e2054 100644
--- a/src/librustc_trans/mir/mod.rs
+++ b/src/librustc_trans/mir/mod.rs
@@ -129,23 +129,23 @@ impl<'a, 'tcx> MirContext<'a, 'tcx> {
         // In order to have a good line stepping behavior in debugger, we overwrite debug
         // locations of macro expansions with that of the outermost expansion site
         // (unless the crate is being compiled with `-Z debug-macros`).
-        if source_info.span.ctxt == NO_EXPANSION ||
+        if source_info.span.ctxt() == NO_EXPANSION ||
            self.ccx.sess().opts.debugging_opts.debug_macros {
-            let scope = self.scope_metadata_for_loc(source_info.scope, source_info.span.lo);
+            let scope = self.scope_metadata_for_loc(source_info.scope, source_info.span.lo());
             (scope, source_info.span)
         } else {
             // Walk up the macro expansion chain until we reach a non-expanded span.
             // We also stop at the function body level because no line stepping can occur
             // at the level above that.
             let mut span = source_info.span;
-            while span.ctxt != NO_EXPANSION && span.ctxt != self.mir.span.ctxt {
-                if let Some(info) = span.ctxt.outer().expn_info() {
+            while span.ctxt() != NO_EXPANSION && span.ctxt() != self.mir.span.ctxt() {
+                if let Some(info) = span.ctxt().outer().expn_info() {
                     span = info.call_site;
                 } else {
                     break;
                 }
             }
-            let scope = self.scope_metadata_for_loc(source_info.scope, span.lo);
+            let scope = self.scope_metadata_for_loc(source_info.scope, span.lo());
             // Use span of the outermost expansion site, while keeping the original lexical scope.
             (scope, span)
         }
@@ -524,15 +524,15 @@ fn arg_local_refs<'a, 'tcx>(bcx: &Builder<'a, 'tcx>,
             }
 
             // Or is it the closure environment?
-            let (closure_ty, env_ref) = if let ty::TyRef(_, mt) = arg_ty.sty {
-                (mt.ty, true)
-            } else {
-                (arg_ty, false)
+            let (closure_ty, env_ref) = match arg_ty.sty {
+                ty::TyRef(_, mt) | ty::TyRawPtr(mt) => (mt.ty, true),
+                _ => (arg_ty, false)
             };
-            let upvar_tys = if let ty::TyClosure(def_id, substs) = closure_ty.sty {
-                substs.upvar_tys(def_id, tcx)
-            } else {
-                bug!("upvar_decls with non-closure arg0 type `{}`", closure_ty);
+
+            let upvar_tys = match closure_ty.sty {
+                ty::TyClosure(def_id, substs) |
+                ty::TyGenerator(def_id, substs, _) => substs.upvar_tys(def_id, tcx),
+                _ => bug!("upvar_decls with non-closure arg0 type `{}`", closure_ty)
             };
 
             // Store the pointer to closure data in an alloca for debuginfo
diff --git a/src/librustc_trans/mir/statement.rs b/src/librustc_trans/mir/statement.rs
index 52dfc8dc4de5c..bbf661ae9a735 100644
--- a/src/librustc_trans/mir/statement.rs
+++ b/src/librustc_trans/mir/statement.rs
@@ -67,11 +67,11 @@ impl<'a, 'tcx> MirContext<'a, 'tcx> {
                     variant_index as u64);
                 bcx
             }
-            mir::StatementKind::StorageLive(ref lvalue) => {
-                self.trans_storage_liveness(bcx, lvalue, base::Lifetime::Start)
+            mir::StatementKind::StorageLive(local) => {
+                self.trans_storage_liveness(bcx, local, base::Lifetime::Start)
             }
-            mir::StatementKind::StorageDead(ref lvalue) => {
-                self.trans_storage_liveness(bcx, lvalue, base::Lifetime::End)
+            mir::StatementKind::StorageDead(local) => {
+                self.trans_storage_liveness(bcx, local, base::Lifetime::End)
             }
             mir::StatementKind::InlineAsm { ref asm, ref outputs, ref inputs } => {
                 let outputs = outputs.iter().map(|output| {
@@ -94,13 +94,11 @@ impl<'a, 'tcx> MirContext<'a, 'tcx> {
 
     fn trans_storage_liveness(&self,
                               bcx: Builder<'a, 'tcx>,
-                              lvalue: &mir::Lvalue<'tcx>,
+                              index: mir::Local,
                               intrinsic: base::Lifetime)
                               -> Builder<'a, 'tcx> {
-        if let mir::Lvalue::Local(index) = *lvalue {
-            if let LocalRef::Lvalue(tr_lval) = self.locals[index] {
-                intrinsic.call(&bcx, tr_lval.llval);
-            }
+        if let LocalRef::Lvalue(tr_lval) = self.locals[index] {
+            intrinsic.call(&bcx, tr_lval.llval);
         }
         bcx
     }
diff --git a/src/librustc_trans/monomorphize.rs b/src/librustc_trans/monomorphize.rs
index b0d8be23b0d96..4989ca8cc938c 100644
--- a/src/librustc_trans/monomorphize.rs
+++ b/src/librustc_trans/monomorphize.rs
@@ -125,6 +125,12 @@ fn resolve_associated_item<'a, 'tcx>(
             let substs = tcx.erase_regions(&substs);
             ty::Instance::new(def_id, substs)
         }
+        traits::VtableGenerator(closure_data) => {
+            Instance {
+                def: ty::InstanceDef::Item(closure_data.closure_def_id),
+                substs: closure_data.substs.substs
+            }
+        }
         traits::VtableClosure(closure_data) => {
             let trait_closure_kind = tcx.lang_items.fn_trait_kind(trait_id).unwrap();
             resolve_closure(scx, closure_data.closure_def_id, closure_data.substs,
diff --git a/src/librustc_trans/trans_item.rs b/src/librustc_trans/trans_item.rs
index 38232ed1d113a..672fa32aa8591 100644
--- a/src/librustc_trans/trans_item.rs
+++ b/src/librustc_trans/trans_item.rs
@@ -504,6 +504,7 @@ impl<'a, 'tcx> DefPathBasedNames<'a, 'tcx> {
                     self.push_type_name(sig.output(), output);
                 }
             },
+            ty::TyGenerator(def_id, ref closure_substs, _) |
             ty::TyClosure(def_id, ref closure_substs) => {
                 self.push_def_path(def_id, output);
                 let generics = self.tcx.generics_of(self.tcx.closure_base_def_id(def_id));
diff --git a/src/librustc_trans/type_of.rs b/src/librustc_trans/type_of.rs
index 9f9126ba83a8f..38c49833e0d75 100644
--- a/src/librustc_trans/type_of.rs
+++ b/src/librustc_trans/type_of.rs
@@ -133,6 +133,11 @@ pub fn in_memory_type_of<'a, 'tcx>(cx: &CrateContext<'a, 'tcx>, t: Ty<'tcx>) ->
           // fill it in *after* placing it into the type cache.
           adt::incomplete_type_of(cx, t, "closure")
       }
+      ty::TyGenerator(..) => {
+          // Only create the named struct, but don't fill it in. We
+          // fill it in *after* placing it into the type cache.
+          adt::incomplete_type_of(cx, t, "generator")
+      }
 
       ty::TyRef(_, ty::TypeAndMut{ty, ..}) |
       ty::TyRawPtr(ty::TypeAndMut{ty, ..}) => {
@@ -197,7 +202,7 @@ pub fn in_memory_type_of<'a, 'tcx>(cx: &CrateContext<'a, 'tcx>, t: Ty<'tcx>) ->
 
     // If this was an enum or struct, fill in the type now.
     match t.sty {
-        ty::TyAdt(..) | ty::TyClosure(..) if !t.is_simd() && !t.is_box() => {
+        ty::TyAdt(..) | ty::TyClosure(..) | ty::TyGenerator(..) if !t.is_simd() && !t.is_box() => {
             adt::finish_type_of(cx, t, &mut llty);
         }
         _ => ()
diff --git a/src/librustc_typeck/check/callee.rs b/src/librustc_typeck/check/callee.rs
index 460e2858b22ec..5b9d4af08e069 100644
--- a/src/librustc_typeck/check/callee.rs
+++ b/src/librustc_typeck/check/callee.rs
@@ -38,6 +38,7 @@ pub fn check_legal_trait_for_method_call(tcx: TyCtxt, span: Span, trait_id: DefI
 enum CallStep<'tcx> {
     Builtin(Ty<'tcx>),
     DeferredClosure(ty::FnSig<'tcx>),
+    /// e.g. enum variant constructors
     Overloaded(MethodCallee<'tcx>),
 }
 
diff --git a/src/librustc_typeck/check/closure.rs b/src/librustc_typeck/check/closure.rs
index 61795a7e623d3..a768271f3b825 100644
--- a/src/librustc_typeck/check/closure.rs
+++ b/src/librustc_typeck/check/closure.rs
@@ -70,22 +70,29 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
         // inference phase (`upvar.rs`).
         let base_substs = Substs::identity_for_item(self.tcx,
             self.tcx.closure_base_def_id(expr_def_id));
-        let closure_type = self.tcx.mk_closure(expr_def_id,
-            base_substs.extend_to(self.tcx, expr_def_id,
+        let substs = base_substs.extend_to(self.tcx, expr_def_id,
                 |_, _| span_bug!(expr.span, "closure has region param"),
                 |_, _| self.infcx.next_ty_var(TypeVariableOrigin::TransformedUpvar(expr.span))
-            )
         );
 
-        debug!("check_closure: expr.id={:?} closure_type={:?}", expr.id, closure_type);
-
         let fn_sig = self.liberate_late_bound_regions(expr_def_id, &sig);
         let fn_sig = self.inh.normalize_associated_types_in(body.value.span,
                                                             body.value.id,
                                                             self.param_env,
                                                             &fn_sig);
 
-        check_fn(self, self.param_env, fn_sig, decl, expr.id, body);
+        let interior = check_fn(self, self.param_env, fn_sig, decl, expr.id, body, true).1;
+
+        if let Some(interior) = interior {
+            let closure_substs = ty::ClosureSubsts {
+                substs: substs,
+            };
+            return self.tcx.mk_generator(expr_def_id, closure_substs, interior);
+        }
+
+        let closure_type = self.tcx.mk_closure(expr_def_id, substs);
+
+        debug!("check_closure: expr.id={:?} closure_type={:?}", expr.id, closure_type);
 
         // Tuple up the arguments and insert the resulting function type into
         // the `closures` table.
diff --git a/src/librustc_typeck/check/compare_method.rs b/src/librustc_typeck/check/compare_method.rs
index bf134f9547d38..b21d48886120c 100644
--- a/src/librustc_typeck/check/compare_method.rs
+++ b/src/librustc_typeck/check/compare_method.rs
@@ -11,7 +11,7 @@
 use rustc::hir::{self, ImplItemKind, TraitItemKind};
 use rustc::infer::{self, InferOk};
 use rustc::middle::free_region::FreeRegionMap;
-use rustc::middle::region::RegionMaps;
+use rustc::middle::region;
 use rustc::ty::{self, TyCtxt};
 use rustc::traits::{self, ObligationCause, ObligationCauseCode, Reveal};
 use rustc::ty::error::{ExpectedFound, TypeError};
@@ -340,10 +340,12 @@ fn compare_predicate_entailment<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
             // region obligations that get overlooked.  The right
             // thing to do is the code below. But we keep this old
             // pass around temporarily.
-            let region_maps = RegionMaps::new();
+            let region_scope_tree = region::ScopeTree::default();
             let mut free_regions = FreeRegionMap::new();
             free_regions.relate_free_regions_from_predicates(&param_env.caller_bounds);
-            infcx.resolve_regions_and_report_errors(impl_m.def_id, &region_maps, &free_regions);
+            infcx.resolve_regions_and_report_errors(impl_m.def_id,
+                                                    &region_scope_tree,
+                                                    &free_regions);
         } else {
             let fcx = FnCtxt::new(&inh, param_env, impl_m_node_id);
             fcx.regionck_item(impl_m_node_id, impl_m_span, &[]);
diff --git a/src/librustc_typeck/check/dropck.rs b/src/librustc_typeck/check/dropck.rs
index 72ff9eb6f5b0d..9bee26a52c0d7 100644
--- a/src/librustc_typeck/check/dropck.rs
+++ b/src/librustc_typeck/check/dropck.rs
@@ -13,7 +13,7 @@ use check::regionck::RegionCtxt;
 use hir::def_id::DefId;
 use middle::free_region::FreeRegionMap;
 use rustc::infer::{self, InferOk};
-use rustc::middle::region::{self, RegionMaps};
+use rustc::middle::region;
 use rustc::ty::subst::{Subst, Substs};
 use rustc::ty::{self, Ty, TyCtxt};
 use rustc::traits::{self, ObligationCause};
@@ -114,9 +114,9 @@ fn ensure_drop_params_and_item_params_correspond<'a, 'tcx>(
             return Err(ErrorReported);
         }
 
-        let region_maps = RegionMaps::new();
+        let region_scope_tree = region::ScopeTree::default();
         let free_regions = FreeRegionMap::new();
-        infcx.resolve_regions_and_report_errors(drop_impl_did, &region_maps, &free_regions);
+        infcx.resolve_regions_and_report_errors(drop_impl_did, &region_scope_tree, &free_regions);
         Ok(())
     })
 }
@@ -270,14 +270,14 @@ pub fn check_safety_of_destructor_if_necessary<'a, 'gcx, 'tcx>(
     rcx: &mut RegionCtxt<'a, 'gcx, 'tcx>,
     ty: ty::Ty<'tcx>,
     span: Span,
-    scope: region::CodeExtent)
+    scope: region::Scope)
     -> Result<(), ErrorReported>
 {
     debug!("check_safety_of_destructor_if_necessary typ: {:?} scope: {:?}",
            ty, scope);
 
 
-    let parent_scope = match rcx.region_maps.opt_encl_scope(scope) {
+    let parent_scope = match rcx.region_scope_tree.opt_encl_scope(scope) {
         Some(parent_scope) => parent_scope,
         // If no enclosing scope, then it must be the root scope
         // which cannot be outlived.
diff --git a/src/librustc_typeck/check/generator_interior.rs b/src/librustc_typeck/check/generator_interior.rs
new file mode 100644
index 0000000000000..88219566792b6
--- /dev/null
+++ b/src/librustc_typeck/check/generator_interior.rs
@@ -0,0 +1,111 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! This calculates the types which has storage which lives across a suspension point in a
+//! generator from the perspective of typeck. The actual types used at runtime
+//! is calculated in `rustc_mir::transform::generator` and may be a subset of the
+//! types computed here.
+
+use rustc::hir::def_id::DefId;
+use rustc::hir::intravisit::{self, Visitor, NestedVisitorMap};
+use rustc::hir::{self, Body, Pat, PatKind, Expr};
+use rustc::middle::region;
+use rustc::ty::Ty;
+use std::rc::Rc;
+use super::FnCtxt;
+use util::nodemap::FxHashMap;
+
+struct InteriorVisitor<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
+    fcx: &'a FnCtxt<'a, 'gcx, 'tcx>,
+    types: FxHashMap<Ty<'tcx>, usize>,
+    region_scope_tree: Rc<region::ScopeTree>,
+}
+
+impl<'a, 'gcx, 'tcx> InteriorVisitor<'a, 'gcx, 'tcx> {
+    fn record(&mut self, ty: Ty<'tcx>, scope: Option<region::Scope>, expr: Option<&'tcx Expr>) {
+        use syntax_pos::DUMMY_SP;
+
+        let live_across_yield = scope.map_or(Some(DUMMY_SP), |s| {
+            self.region_scope_tree.yield_in_scope(s)
+        });
+
+        if let Some(span) = live_across_yield {
+            let ty = self.fcx.resolve_type_vars_if_possible(&ty);
+
+            debug!("type in expr = {:?}, scope = {:?}, type = {:?}, span = {:?}",
+                   expr, scope, ty, span);
+
+            // Map the type to the number of types added before it
+            let entries = self.types.len();
+            self.types.entry(&ty).or_insert(entries);
+        } else {
+            debug!("no type in expr = {:?}, span = {:?}", expr, expr.map(|e| e.span));
+        }
+    }
+}
+
+pub fn resolve_interior<'a, 'gcx, 'tcx>(fcx: &'a FnCtxt<'a, 'gcx, 'tcx>,
+                                        def_id: DefId,
+                                        body_id: hir::BodyId,
+                                        witness: Ty<'tcx>) {
+    let body = fcx.tcx.hir.body(body_id);
+    let mut visitor = InteriorVisitor {
+        fcx,
+        types: FxHashMap(),
+        region_scope_tree: fcx.tcx.region_scope_tree(def_id),
+    };
+    intravisit::walk_body(&mut visitor, body);
+
+    let mut types: Vec<_> = visitor.types.drain().collect();
+
+    // Sort types by insertion order
+    types.sort_by_key(|t| t.1);
+
+    // Extract type components
+    let types: Vec<_> = types.into_iter().map(|t| t.0).collect();
+
+    let tuple = fcx.tcx.intern_tup(&types, false);
+
+    debug!("Types in generator {:?}, span = {:?}", tuple, body.value.span);
+
+    // Unify the tuple with the witness
+    match fcx.at(&fcx.misc(body.value.span), fcx.param_env).eq(witness, tuple) {
+        Ok(ok) => fcx.register_infer_ok_obligations(ok),
+        _ => bug!(),
+   }
+}
+
+impl<'a, 'gcx, 'tcx> Visitor<'tcx> for InteriorVisitor<'a, 'gcx, 'tcx> {
+    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+        NestedVisitorMap::None
+    }
+
+    fn visit_body(&mut self, _body: &'tcx Body) {
+        // Closures inside are not considered part of the generator interior
+    }
+
+    fn visit_pat(&mut self, pat: &'tcx Pat) {
+        if let PatKind::Binding(..) = pat.node {
+            let scope = self.region_scope_tree.var_scope(pat.hir_id.local_id);
+            let ty = self.fcx.tables.borrow().pat_ty(pat);
+            self.record(ty, Some(scope), None);
+        }
+
+        intravisit::walk_pat(self, pat);
+    }
+
+    fn visit_expr(&mut self, expr: &'tcx Expr) {
+        let scope = self.region_scope_tree.temporary_scope(expr.hir_id.local_id);
+        let ty = self.fcx.tables.borrow().expr_ty_adjusted(expr);
+        self.record(ty, scope, Some(expr));
+
+        intravisit::walk_expr(self, expr);
+    }
+}
diff --git a/src/librustc_typeck/check/intrinsic.rs b/src/librustc_typeck/check/intrinsic.rs
index 96643ae72abad..6fee7e58633fc 100644
--- a/src/librustc_typeck/check/intrinsic.rs
+++ b/src/librustc_typeck/check/intrinsic.rs
@@ -313,6 +313,11 @@ pub fn check_intrinsic_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                 (0, vec![tcx.mk_fn_ptr(fn_ty), mut_u8, mut_u8], tcx.types.i32)
             }
 
+            "align_offset" => {
+                let ptr_ty = tcx.mk_imm_ptr(tcx.mk_nil());
+                (0, vec![ptr_ty, tcx.types.usize], tcx.types.usize)
+            },
+
             ref other => {
                 struct_span_err!(tcx.sess, it.span, E0093,
                                 "unrecognized intrinsic function: `{}`",
diff --git a/src/librustc_typeck/check/method/confirm.rs b/src/librustc_typeck/check/method/confirm.rs
index db383b6305b4a..08ec3bf74a71d 100644
--- a/src/librustc_typeck/check/method/confirm.rs
+++ b/src/librustc_typeck/check/method/confirm.rs
@@ -232,24 +232,6 @@ impl<'a, 'gcx, 'tcx> ConfirmContext<'a, 'gcx, 'tcx> {
                 })
             }
 
-            probe::ExtensionImplPick(impl_def_id) => {
-                // The method being invoked is the method as defined on the trait,
-                // so return the substitutions from the trait. Consider:
-                //
-                //     impl<A,B,C> Trait<A,B> for Foo<C> { ... }
-                //
-                // If we instantiate A, B, and C with $A, $B, and $C
-                // respectively, then we want to return the type
-                // parameters from the trait ([$A,$B]), not those from
-                // the impl ([$A,$B,$C]) not the receiver type ([$C]).
-                let impl_polytype = self.impl_self_ty(self.span, impl_def_id);
-                let impl_trait_ref =
-                    self.instantiate_type_scheme(self.span,
-                                                 impl_polytype.substs,
-                                                 &self.tcx.impl_trait_ref(impl_def_id).unwrap());
-                impl_trait_ref.substs
-            }
-
             probe::TraitPick => {
                 let trait_def_id = pick.item.container.id();
 
diff --git a/src/librustc_typeck/check/method/mod.rs b/src/librustc_typeck/check/method/mod.rs
index 819f48a1b57e8..31ceed5b965bf 100644
--- a/src/librustc_typeck/check/method/mod.rs
+++ b/src/librustc_typeck/check/method/mod.rs
@@ -52,10 +52,6 @@ pub enum MethodError<'tcx> {
     // Multiple methods might apply.
     Ambiguity(Vec<CandidateSource>),
 
-    // Using a `Fn`/`FnMut`/etc method on a raw closure type before we have inferred its kind.
-    ClosureAmbiguity(// DefId of fn trait
-                     DefId),
-
     // Found an applicable method, but it is not visible. The second argument contains a list of
     // not-in-scope traits which may work.
     PrivateMatch(Def, Vec<DefId>),
@@ -63,6 +59,9 @@ pub enum MethodError<'tcx> {
     // Found a `Self: Sized` bound where `Self` is a trait object, also the caller may have
     // forgotten to import a trait.
     IllegalSizedBound(Vec<DefId>),
+
+    // Found a match, but the return type is wrong
+    BadReturnType,
 }
 
 // Contains a list of static methods that may apply, a list of unsatisfied trait predicates which
@@ -113,9 +112,12 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
             Ok(..) => true,
             Err(NoMatch(..)) => false,
             Err(Ambiguity(..)) => true,
-            Err(ClosureAmbiguity(..)) => true,
             Err(PrivateMatch(..)) => allow_private,
             Err(IllegalSizedBound(..)) => true,
+            Err(BadReturnType) => {
+                bug!("no return type expectations but got BadReturnType")
+            }
+
         }
     }
 
diff --git a/src/librustc_typeck/check/method/probe.rs b/src/librustc_typeck/check/method/probe.rs
index 096b778cab2d3..ba74c902f55e0 100644
--- a/src/librustc_typeck/check/method/probe.rs
+++ b/src/librustc_typeck/check/method/probe.rs
@@ -18,7 +18,7 @@ use hir::def_id::DefId;
 use hir::def::Def;
 use rustc::ty::subst::{Subst, Substs};
 use rustc::traits::{self, ObligationCause};
-use rustc::ty::{self, Ty, ToPolyTraitRef, TraitRef, TypeFoldable};
+use rustc::ty::{self, Ty, ToPolyTraitRef, ToPredicate, TraitRef, TypeFoldable};
 use rustc::infer::type_variable::TypeVariableOrigin;
 use rustc::util::nodemap::FxHashSet;
 use rustc::infer::{self, InferOk};
@@ -32,15 +32,6 @@ use std::rc::Rc;
 use self::CandidateKind::*;
 pub use self::PickKind::*;
 
-pub enum LookingFor<'tcx> {
-    /// looking for methods with the given name; this is the normal case
-    MethodName(ast::Name),
-
-    /// looking for methods that return a given type; this is used to
-    /// assemble suggestions
-    ReturnType(Ty<'tcx>),
-}
-
 /// Boolean flag used to indicate if this search is for a suggestion
 /// or not.  If true, we can allow ambiguity and so forth.
 pub struct IsSuggestion(pub bool);
@@ -49,9 +40,9 @@ struct ProbeContext<'a, 'gcx: 'a + 'tcx, 'tcx: 'a> {
     fcx: &'a FnCtxt<'a, 'gcx, 'tcx>,
     span: Span,
     mode: Mode,
-    looking_for: LookingFor<'tcx>,
+    method_name: Option<ast::Name>,
+    return_type: Option<Ty<'tcx>>,
     steps: Rc<Vec<CandidateStep<'tcx>>>,
-    opt_simplified_steps: Option<Vec<ty::fast_reject::SimplifiedType>>,
     inherent_candidates: Vec<Candidate<'tcx>>,
     extension_candidates: Vec<Candidate<'tcx>>,
     impl_dups: FxHashSet<DefId>,
@@ -85,6 +76,7 @@ struct CandidateStep<'tcx> {
 #[derive(Debug)]
 struct Candidate<'tcx> {
     xform_self_ty: Ty<'tcx>,
+    xform_ret_ty: Option<Ty<'tcx>>,
     item: ty::AssociatedItem,
     kind: CandidateKind<'tcx>,
     import_id: Option<ast::NodeId>,
@@ -95,17 +87,19 @@ enum CandidateKind<'tcx> {
     InherentImplCandidate(&'tcx Substs<'tcx>,
                           // Normalize obligations
                           Vec<traits::PredicateObligation<'tcx>>),
-    ExtensionImplCandidate(// Impl
-                           DefId,
-                           &'tcx Substs<'tcx>,
-                           // Normalize obligations
-                           Vec<traits::PredicateObligation<'tcx>>),
     ObjectCandidate,
-    TraitCandidate,
+    TraitCandidate(ty::TraitRef<'tcx>),
     WhereClauseCandidate(// Trait
                          ty::PolyTraitRef<'tcx>),
 }
 
+#[derive(Debug, PartialEq, Eq, Copy, Clone)]
+enum ProbeResult {
+    NoMatch,
+    BadReturnType,
+    Match,
+}
+
 #[derive(Debug, PartialEq, Eq, Clone)]
 pub struct Pick<'tcx> {
     pub item: ty::AssociatedItem,
@@ -133,8 +127,6 @@ pub struct Pick<'tcx> {
 #[derive(Clone, Debug, PartialEq, Eq)]
 pub enum PickKind<'tcx> {
     InherentImplPick,
-    ExtensionImplPick(// Impl
-                      DefId),
     ObjectPick,
     TraitPick,
     WhereClausePick(// Trait
@@ -183,19 +175,19 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                return_type,
                scope_expr_id);
         let method_names =
-            self.probe_op(span, mode, LookingFor::ReturnType(return_type), IsSuggestion(true),
+            self.probe_op(span, mode, None, Some(return_type), IsSuggestion(true),
                           self_ty, scope_expr_id, ProbeScope::TraitsInScope,
                           |probe_cx| Ok(probe_cx.candidate_method_names()))
                 .unwrap_or(vec![]);
-        method_names
-            .iter()
-            .flat_map(|&method_name| {
-                match self.probe_for_name(span, mode, method_name, IsSuggestion(true), self_ty,
-                                          scope_expr_id, ProbeScope::TraitsInScope) {
-                    Ok(pick) => Some(pick.item),
-                    Err(_) => None,
-                }
-            })
+         method_names
+             .iter()
+             .flat_map(|&method_name| {
+                 self.probe_op(
+                     span, mode, Some(method_name), Some(return_type),
+                     IsSuggestion(true), self_ty, scope_expr_id,
+                     ProbeScope::TraitsInScope, |probe_cx| probe_cx.pick()
+                 ).ok().map(|pick| pick.item)
+             })
             .collect()
     }
 
@@ -214,7 +206,8 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                scope_expr_id);
         self.probe_op(span,
                       mode,
-                      LookingFor::MethodName(item_name),
+                      Some(item_name),
+                      None,
                       is_suggestion,
                       self_ty,
                       scope_expr_id,
@@ -225,7 +218,8 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
     fn probe_op<OP,R>(&'a self,
                       span: Span,
                       mode: Mode,
-                      looking_for: LookingFor<'tcx>,
+                      method_name: Option<ast::Name>,
+                      return_type: Option<Ty<'tcx>>,
                       is_suggestion: IsSuggestion,
                       self_ty: Ty<'tcx>,
                       scope_expr_id: ast::NodeId,
@@ -259,24 +253,6 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                  }]
         };
 
-        // Create a list of simplified self types, if we can.
-        let mut simplified_steps = Vec::new();
-        for step in &steps {
-            match ty::fast_reject::simplify_type(self.tcx, step.self_ty, true) {
-                None => {
-                    break;
-                }
-                Some(simplified_type) => {
-                    simplified_steps.push(simplified_type);
-                }
-            }
-        }
-        let opt_simplified_steps = if simplified_steps.len() < steps.len() {
-            None // failed to convert at least one of the steps
-        } else {
-            Some(simplified_steps)
-        };
-
         debug!("ProbeContext: steps for self_ty={:?} are {:?}",
                self_ty,
                steps);
@@ -285,8 +261,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
         // that we create during the probe process are removed later
         self.probe(|_| {
             let mut probe_cx =
-                ProbeContext::new(self, span, mode, looking_for,
-                                  steps, opt_simplified_steps);
+                ProbeContext::new(self, span, mode, method_name, return_type, steps);
 
             probe_cx.assemble_inherent_candidates();
             match scope {
@@ -356,20 +331,20 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
     fn new(fcx: &'a FnCtxt<'a, 'gcx, 'tcx>,
            span: Span,
            mode: Mode,
-           looking_for: LookingFor<'tcx>,
-           steps: Vec<CandidateStep<'tcx>>,
-           opt_simplified_steps: Option<Vec<ty::fast_reject::SimplifiedType>>)
+           method_name: Option<ast::Name>,
+           return_type: Option<Ty<'tcx>>,
+           steps: Vec<CandidateStep<'tcx>>)
            -> ProbeContext<'a, 'gcx, 'tcx> {
         ProbeContext {
             fcx,
             span,
             mode,
-            looking_for,
+            method_name,
+            return_type,
             inherent_candidates: Vec::new(),
             extension_candidates: Vec::new(),
             impl_dups: FxHashSet(),
             steps: Rc::new(steps),
-            opt_simplified_steps,
             static_candidates: Vec::new(),
             private_candidate: None,
             unsatisfied_predicates: Vec::new(),
@@ -387,33 +362,25 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
     ///////////////////////////////////////////////////////////////////////////
     // CANDIDATE ASSEMBLY
 
-    fn push_inherent_candidate(&mut self, xform_self_ty: Ty<'tcx>, item: ty::AssociatedItem,
-                               kind: CandidateKind<'tcx>, import_id: Option<ast::NodeId>) {
-        let is_accessible = if let LookingFor::MethodName(name) = self.looking_for {
-            let def_scope = self.tcx.adjust(name, item.container.id(), self.body_id).1;
-            item.vis.is_accessible_from(def_scope, self.tcx)
-        } else {
-            true
-        };
-        if is_accessible {
-            self.inherent_candidates.push(Candidate { xform_self_ty, item, kind, import_id });
-        } else if self.private_candidate.is_none() {
-            self.private_candidate = Some(item.def());
-        }
-    }
-
-    fn push_extension_candidate(&mut self, xform_self_ty: Ty<'tcx>, item: ty::AssociatedItem,
-                               kind: CandidateKind<'tcx>, import_id: Option<ast::NodeId>) {
-        let is_accessible = if let LookingFor::MethodName(name) = self.looking_for {
+    fn push_candidate(&mut self,
+                      candidate: Candidate<'tcx>,
+                      is_inherent: bool)
+    {
+        let is_accessible = if let Some(name) = self.method_name {
+            let item = candidate.item;
             let def_scope = self.tcx.adjust(name, item.container.id(), self.body_id).1;
             item.vis.is_accessible_from(def_scope, self.tcx)
         } else {
             true
         };
         if is_accessible {
-            self.extension_candidates.push(Candidate { xform_self_ty, item, kind, import_id });
+            if is_inherent {
+                self.inherent_candidates.push(candidate);
+            } else {
+                self.extension_candidates.push(candidate);
+            }
         } else if self.private_candidate.is_none() {
-            self.private_candidate = Some(item.def());
+            self.private_candidate = Some(candidate.item.def());
         }
     }
 
@@ -551,19 +518,22 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
             let impl_ty = impl_ty.subst(self.tcx, impl_substs);
 
             // Determine the receiver type that the method itself expects.
-            let xform_self_ty = self.xform_self_ty(&item, impl_ty, impl_substs);
+            let xform_tys = self.xform_self_ty(&item, impl_ty, impl_substs);
 
             // We can't use normalize_associated_types_in as it will pollute the
             // fcx's fulfillment context after this probe is over.
             let cause = traits::ObligationCause::misc(self.span, self.body_id);
             let selcx = &mut traits::SelectionContext::new(self.fcx);
-            let traits::Normalized { value: xform_self_ty, obligations } =
-                traits::normalize(selcx, self.param_env, cause, &xform_self_ty);
-            debug!("assemble_inherent_impl_probe: xform_self_ty = {:?}",
-                   xform_self_ty);
-
-            self.push_inherent_candidate(xform_self_ty, item,
-                                         InherentImplCandidate(impl_substs, obligations), None);
+            let traits::Normalized { value: (xform_self_ty, xform_ret_ty), obligations } =
+                traits::normalize(selcx, self.param_env, cause, &xform_tys);
+            debug!("assemble_inherent_impl_probe: xform_self_ty = {:?}/{:?}",
+                   xform_self_ty, xform_ret_ty);
+
+            self.push_candidate(Candidate {
+                xform_self_ty, xform_ret_ty, item,
+                kind: InherentImplCandidate(impl_substs, obligations),
+                import_id: None
+            }, true);
         }
     }
 
@@ -584,10 +554,13 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
         self.elaborate_bounds(&[trait_ref], |this, new_trait_ref, item| {
             let new_trait_ref = this.erase_late_bound_regions(&new_trait_ref);
 
-            let xform_self_ty =
+            let (xform_self_ty, xform_ret_ty) =
                 this.xform_self_ty(&item, new_trait_ref.self_ty(), new_trait_ref.substs);
-
-            this.push_inherent_candidate(xform_self_ty, item, ObjectCandidate, None);
+            this.push_candidate(Candidate {
+                xform_self_ty, xform_ret_ty, item,
+                kind: ObjectCandidate,
+                import_id: None
+            }, true);
         });
     }
 
@@ -624,7 +597,8 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
         self.elaborate_bounds(&bounds, |this, poly_trait_ref, item| {
             let trait_ref = this.erase_late_bound_regions(&poly_trait_ref);
 
-            let xform_self_ty = this.xform_self_ty(&item, trait_ref.self_ty(), trait_ref.substs);
+            let (xform_self_ty, xform_ret_ty) =
+                this.xform_self_ty(&item, trait_ref.self_ty(), trait_ref.substs);
 
             // Because this trait derives from a where-clause, it
             // should not contain any inference variables or other
@@ -633,8 +607,11 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
             // `WhereClausePick`.
             assert!(!trait_ref.substs.needs_infer());
 
-            this.push_inherent_candidate(xform_self_ty, item,
-                                         WhereClauseCandidate(poly_trait_ref), None);
+            this.push_candidate(Candidate {
+                xform_self_ty, xform_ret_ty, item,
+                kind: WhereClauseCandidate(poly_trait_ref),
+                import_id: None
+            }, true);
         });
     }
 
@@ -662,10 +639,14 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
     fn assemble_extension_candidates_for_traits_in_scope(&mut self,
                                                          expr_id: ast::NodeId)
                                                          -> Result<(), MethodError<'tcx>> {
+        if expr_id == ast::DUMMY_NODE_ID {
+            return Ok(())
+        }
         let mut duplicates = FxHashSet();
-        let opt_applicable_traits = self.tcx.trait_map.get(&expr_id);
+        let expr_hir_id = self.tcx.hir.node_to_hir_id(expr_id);
+        let opt_applicable_traits = self.tcx.in_scope_traits(expr_hir_id);
         if let Some(applicable_traits) = opt_applicable_traits {
-            for trait_candidate in applicable_traits {
+            for trait_candidate in applicable_traits.iter() {
                 let trait_did = trait_candidate.def_id;
                 if duplicates.insert(trait_did) {
                     let import_id = trait_candidate.import_id;
@@ -687,17 +668,27 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
         Ok(())
     }
 
-    pub fn matches_return_type(&self, method: &ty::AssociatedItem,
-                               expected: ty::Ty<'tcx>) -> bool {
+    pub fn matches_return_type(&self,
+                               method: &ty::AssociatedItem,
+                               self_ty: Option<Ty<'tcx>>,
+                               expected: Ty<'tcx>) -> bool {
         match method.def() {
             Def::Method(def_id) => {
                 let fty = self.tcx.fn_sig(def_id);
                 self.probe(|_| {
                     let substs = self.fresh_substs_for_item(self.span, method.def_id);
-                    let output = fty.output().subst(self.tcx, substs);
-                    let (output, _) = self.replace_late_bound_regions_with_fresh_var(
-                        self.span, infer::FnCall, &output);
-                    self.can_sub(self.param_env, output, expected).is_ok()
+                    let fty = fty.subst(self.tcx, substs);
+                    let (fty, _) = self.replace_late_bound_regions_with_fresh_var(
+                        self.span, infer::FnCall, &fty);
+
+                    if let Some(self_ty) = self_ty {
+                        if let Err(_) = self.at(&ObligationCause::dummy(), self.param_env)
+                            .sup(fty.inputs()[0], self_ty)
+                        {
+                            return false
+                        }
+                    }
+                    self.can_sub(self.param_env, fty.output(), expected).is_ok()
                 })
             }
             _ => false,
@@ -710,6 +701,8 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
                                                -> Result<(), MethodError<'tcx>> {
         debug!("assemble_extension_candidates_for_trait(trait_def_id={:?})",
                trait_def_id);
+        let trait_substs = self.fresh_item_substs(trait_def_id);
+        let trait_ref = ty::TraitRef::new(trait_def_id, trait_substs);
 
         for item in self.impl_or_trait_item(trait_def_id) {
             // Check whether `trait_def_id` defines a method with suitable name:
@@ -719,282 +712,31 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
                 continue;
             }
 
-            self.assemble_builtin_candidates(import_id, trait_def_id, item.clone());
-
-            self.assemble_extension_candidates_for_trait_impls(import_id, trait_def_id,
-                                                               item.clone());
-
-            self.assemble_closure_candidates(import_id, trait_def_id, item.clone())?;
-
-            self.assemble_projection_candidates(import_id, trait_def_id, item.clone());
-
-            self.assemble_where_clause_candidates(import_id, trait_def_id, item.clone());
-        }
-
-        Ok(())
-    }
-
-    fn assemble_builtin_candidates(&mut self,
-                                   import_id: Option<ast::NodeId>,
-                                   trait_def_id: DefId,
-                                   item: ty::AssociatedItem) {
-        if Some(trait_def_id) == self.tcx.lang_items.clone_trait() {
-            self.assemble_builtin_clone_candidates(import_id, trait_def_id, item);
-        }
-    }
-
-    fn assemble_builtin_clone_candidates(&mut self,
-                                         import_id: Option<ast::NodeId>,
-                                         trait_def_id: DefId,
-                                         item: ty::AssociatedItem) {
-        for step in Rc::clone(&self.steps).iter() {
-            match step.self_ty.sty {
-                ty::TyInfer(ty::IntVar(_)) | ty::TyInfer(ty::FloatVar(_)) |
-                ty::TyUint(_) | ty::TyInt(_) | ty::TyBool | ty::TyFloat(_) |
-                ty::TyFnDef(..) | ty::TyFnPtr(_) | ty::TyChar |
-                ty::TyRawPtr(..) | ty::TyError | ty::TyNever |
-                ty::TyRef(_, ty::TypeAndMut { ty: _, mutbl: hir::MutImmutable }) |
-                ty::TyArray(..) | ty::TyTuple(..) => {
-                    ()
-                }
-
-                _ => continue,
-            };
-
-            let substs = Substs::for_item(self.tcx,
-                                          trait_def_id,
-                                          |def, _| self.region_var_for_def(self.span, def),
-                                          |def, substs| {
-                if def.index == 0 {
-                    step.self_ty
-                } else {
-                    self.type_var_for_def(self.span, def, substs)
-                }
-            });
-
-            let xform_self_ty = self.xform_self_ty(&item, step.self_ty, substs);
-            self.push_inherent_candidate(xform_self_ty, item, TraitCandidate, import_id);
-        }
-    }
-
-    fn assemble_extension_candidates_for_trait_impls(&mut self,
-                                                     import_id: Option<ast::NodeId>,
-                                                     trait_def_id: DefId,
-                                                     item: ty::AssociatedItem) {
-        // FIXME(arielb1): can we use for_each_relevant_impl here?
-        self.tcx.for_each_impl(trait_def_id, |impl_def_id| {
-            debug!("assemble_extension_candidates_for_trait_impl: trait_def_id={:?} \
-                                                                  impl_def_id={:?}",
-                   trait_def_id,
-                   impl_def_id);
-
-            if !self.impl_can_possibly_match(impl_def_id) {
-                return;
-            }
-
-            let (_, impl_substs) = self.impl_ty_and_substs(impl_def_id);
-
-            debug!("impl_substs={:?}", impl_substs);
-
-            let impl_trait_ref = self.tcx.impl_trait_ref(impl_def_id)
-                .unwrap() // we know this is a trait impl
-                .subst(self.tcx, impl_substs);
-
-            debug!("impl_trait_ref={:?}", impl_trait_ref);
-
-            // Determine the receiver type that the method itself expects.
-            let xform_self_ty =
-                self.xform_self_ty(&item, impl_trait_ref.self_ty(), impl_trait_ref.substs);
-
-            // Normalize the receiver. We can't use normalize_associated_types_in
-            // as it will pollute the fcx's fulfillment context after this probe
-            // is over.
-            let cause = traits::ObligationCause::misc(self.span, self.body_id);
-            let selcx = &mut traits::SelectionContext::new(self.fcx);
-            let traits::Normalized { value: xform_self_ty, obligations } =
-                traits::normalize(selcx, self.param_env, cause, &xform_self_ty);
-
-            debug!("xform_self_ty={:?}", xform_self_ty);
-
-            self.push_extension_candidate(xform_self_ty, item,
-                        ExtensionImplCandidate(impl_def_id, impl_substs, obligations), import_id);
-        });
-    }
-
-    fn impl_can_possibly_match(&self, impl_def_id: DefId) -> bool {
-        let simplified_steps = match self.opt_simplified_steps {
-            Some(ref simplified_steps) => simplified_steps,
-            None => {
-                return true;
-            }
-        };
-
-        let impl_type = self.tcx.type_of(impl_def_id);
-        let impl_simplified_type =
-            match ty::fast_reject::simplify_type(self.tcx, impl_type, false) {
-                Some(simplified_type) => simplified_type,
-                None => {
-                    return true;
-                }
-            };
-
-        simplified_steps.contains(&impl_simplified_type)
-    }
-
-    fn assemble_closure_candidates(&mut self,
-                                   import_id: Option<ast::NodeId>,
-                                   trait_def_id: DefId,
-                                   item: ty::AssociatedItem)
-                                   -> Result<(), MethodError<'tcx>> {
-        // Check if this is one of the Fn,FnMut,FnOnce traits.
-        let tcx = self.tcx;
-        let kind = if Some(trait_def_id) == tcx.lang_items.fn_trait() {
-            ty::ClosureKind::Fn
-        } else if Some(trait_def_id) == tcx.lang_items.fn_mut_trait() {
-            ty::ClosureKind::FnMut
-        } else if Some(trait_def_id) == tcx.lang_items.fn_once_trait() {
-            ty::ClosureKind::FnOnce
-        } else {
-            return Ok(());
-        };
-
-        // Check if there is an unboxed-closure self-type in the list of receivers.
-        // If so, add "synthetic impls".
-        let steps = self.steps.clone();
-        for step in steps.iter() {
-            let closure_id = match step.self_ty.sty {
-                ty::TyClosure(def_id, _) => {
-                    if let Some(id) = self.tcx.hir.as_local_node_id(def_id) {
-                        self.tcx.hir.node_to_hir_id(id)
-                    } else {
-                        continue;
-                    }
-                }
-                _ => continue,
-            };
-
-            let closure_kind = {
-                match self.tables.borrow().closure_kinds().get(closure_id) {
-                    Some(&(k, _)) => k,
-                    None => {
-                        return Err(MethodError::ClosureAmbiguity(trait_def_id));
-                    }
-                }
-            };
-
-            // this closure doesn't implement the right kind of `Fn` trait
-            if !closure_kind.extends(kind) {
-                continue;
-            }
-
-            // create some substitutions for the argument/return type;
-            // for the purposes of our method lookup, we only take
-            // receiver type into account, so we can just substitute
-            // fresh types here to use during substitution and subtyping.
-            let substs = Substs::for_item(self.tcx,
-                                          trait_def_id,
-                                          |def, _| self.region_var_for_def(self.span, def),
-                                          |def, substs| {
-                if def.index == 0 {
-                    step.self_ty
-                } else {
-                    self.type_var_for_def(self.span, def, substs)
-                }
-            });
-
-            let xform_self_ty = self.xform_self_ty(&item, step.self_ty, substs);
-            self.push_inherent_candidate(xform_self_ty, item, TraitCandidate, import_id);
+            let (xform_self_ty, xform_ret_ty) =
+                self.xform_self_ty(&item, trait_ref.self_ty(), trait_substs);
+            self.push_candidate(Candidate {
+                xform_self_ty, xform_ret_ty, item, import_id,
+                kind: TraitCandidate(trait_ref),
+            }, false);
         }
-
         Ok(())
     }
 
-    fn assemble_projection_candidates(&mut self,
-                                      import_id: Option<ast::NodeId>,
-                                      trait_def_id: DefId,
-                                      item: ty::AssociatedItem) {
-        debug!("assemble_projection_candidates(\
-               trait_def_id={:?}, \
-               item={:?})",
-               trait_def_id,
-               item);
-
-        for step in Rc::clone(&self.steps).iter() {
-            debug!("assemble_projection_candidates: step={:?}", step);
-
-            let (def_id, substs) = match step.self_ty.sty {
-                ty::TyProjection(ref data) => {
-                    let trait_ref = data.trait_ref(self.tcx);
-                    (trait_ref.def_id, trait_ref.substs)
-                },
-                ty::TyAnon(def_id, substs) => (def_id, substs),
-                _ => continue,
-            };
-
-            debug!("assemble_projection_candidates: def_id={:?} substs={:?}",
-                   def_id,
-                   substs);
-
-            let trait_predicates = self.tcx.predicates_of(def_id);
-            let bounds = trait_predicates.instantiate(self.tcx, substs);
-            let predicates = bounds.predicates;
-            debug!("assemble_projection_candidates: predicates={:?}",
-                   predicates);
-            for poly_bound in traits::elaborate_predicates(self.tcx, predicates)
-                .filter_map(|p| p.to_opt_poly_trait_ref())
-                .filter(|b| b.def_id() == trait_def_id) {
-                let bound = self.erase_late_bound_regions(&poly_bound);
-
-                debug!("assemble_projection_candidates: def_id={:?} substs={:?} bound={:?}",
-                       def_id,
-                       substs,
-                       bound);
-
-                if self.can_eq(self.param_env, step.self_ty, bound.self_ty()).is_ok() {
-                    let xform_self_ty = self.xform_self_ty(&item, bound.self_ty(), bound.substs);
-
-                    debug!("assemble_projection_candidates: bound={:?} xform_self_ty={:?}",
-                           bound,
-                           xform_self_ty);
-
-                    self.push_extension_candidate(xform_self_ty, item, TraitCandidate, import_id);
-                }
-            }
-        }
-    }
-
-    fn assemble_where_clause_candidates(&mut self,
-                                        import_id: Option<ast::NodeId>,
-                                        trait_def_id: DefId,
-                                        item: ty::AssociatedItem) {
-        debug!("assemble_where_clause_candidates(trait_def_id={:?})",
-               trait_def_id);
-
-        let caller_predicates = self.param_env.caller_bounds.to_vec();
-        for poly_bound in traits::elaborate_predicates(self.tcx, caller_predicates)
-            .filter_map(|p| p.to_opt_poly_trait_ref())
-            .filter(|b| b.def_id() == trait_def_id) {
-            let bound = self.erase_late_bound_regions(&poly_bound);
-            let xform_self_ty = self.xform_self_ty(&item, bound.self_ty(), bound.substs);
-
-            debug!("assemble_where_clause_candidates: bound={:?} xform_self_ty={:?}",
-                   bound,
-                   xform_self_ty);
-
-            self.push_extension_candidate(xform_self_ty, item,
-                                          WhereClauseCandidate(poly_bound), import_id);
-        }
-    }
-
     fn candidate_method_names(&self) -> Vec<ast::Name> {
         let mut set = FxHashSet();
-        let mut names: Vec<_> =
-            self.inherent_candidates
-                .iter()
-                .chain(&self.extension_candidates)
-                .map(|candidate| candidate.item.name)
-                .filter(|&name| set.insert(name))
-                .collect();
+        let mut names: Vec<_> = self.inherent_candidates
+            .iter()
+            .chain(&self.extension_candidates)
+            .filter(|candidate| {
+                if let Some(return_ty) = self.return_type {
+                    self.matches_return_type(&candidate.item, None, return_ty)
+                } else {
+                    true
+                }
+            })
+            .map(|candidate| candidate.item.name)
+            .filter(|&name| set.insert(name))
+            .collect();
 
         // sort them by the name so we have a stable result
         names.sort_by_key(|n| n.as_str());
@@ -1005,10 +747,7 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
     // THE ACTUAL SEARCH
 
     fn pick(mut self) -> PickResult<'tcx> {
-        assert!(match self.looking_for {
-            LookingFor::MethodName(_) => true,
-            LookingFor::ReturnType(_) => false,
-        });
+        assert!(self.method_name.is_some());
 
         if let Some(r) = self.pick_core() {
             return r;
@@ -1051,10 +790,6 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
                 assert!(others.is_empty());
                 vec![]
             }
-            Some(Err(MethodError::ClosureAmbiguity(..))) => {
-                // this error only occurs when assembling candidates
-                span_bug!(span, "encountered ClosureAmbiguity from pick_core");
-            }
             _ => vec![],
         };
 
@@ -1072,21 +807,17 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
         let steps = self.steps.clone();
 
         // find the first step that works
-        steps.iter().filter_map(|step| self.pick_step(step)).next()
-    }
-
-    fn pick_step(&mut self, step: &CandidateStep<'tcx>) -> Option<PickResult<'tcx>> {
-        debug!("pick_step: step={:?}", step);
-
-        if step.self_ty.references_error() {
-            return None;
-        }
-
-        if let Some(result) = self.pick_by_value_method(step) {
-            return Some(result);
-        }
-
-        self.pick_autorefd_method(step)
+        steps
+            .iter()
+            .filter(|step| {
+                debug!("pick_core: step={:?}", step);
+                !step.self_ty.references_error()
+            }).flat_map(|step| {
+                self.pick_by_value_method(step).or_else(|| {
+                self.pick_autorefd_method(step, hir::MutImmutable).or_else(|| {
+                self.pick_autorefd_method(step, hir::MutMutable)
+            })})})
+            .next()
     }
 
     fn pick_by_value_method(&mut self, step: &CandidateStep<'tcx>) -> Option<PickResult<'tcx>> {
@@ -1117,36 +848,30 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
         })
     }
 
-    fn pick_autorefd_method(&mut self, step: &CandidateStep<'tcx>) -> Option<PickResult<'tcx>> {
+    fn pick_autorefd_method(&mut self, step: &CandidateStep<'tcx>, mutbl: hir::Mutability)
+                            -> Option<PickResult<'tcx>> {
         let tcx = self.tcx;
 
         // In general, during probing we erase regions. See
         // `impl_self_ty()` for an explanation.
         let region = tcx.types.re_erased;
 
-        // Search through mutabilities in order to find one where pick works:
-        [hir::MutImmutable, hir::MutMutable]
-            .iter()
-            .filter_map(|&m| {
-                let autoref_ty = tcx.mk_ref(region,
-                                            ty::TypeAndMut {
-                                                ty: step.self_ty,
-                                                mutbl: m,
-                                            });
-                self.pick_method(autoref_ty).map(|r| {
-                    r.map(|mut pick| {
-                        pick.autoderefs = step.autoderefs;
-                        pick.autoref = Some(m);
-                        pick.unsize = if step.unsize {
-                            Some(step.self_ty)
-                        } else {
-                            None
-                        };
-                        pick
-                    })
-                })
+        let autoref_ty = tcx.mk_ref(region,
+                                    ty::TypeAndMut {
+                                        ty: step.self_ty, mutbl
+                                    });
+        self.pick_method(autoref_ty).map(|r| {
+            r.map(|mut pick| {
+                pick.autoderefs = step.autoderefs;
+                pick.autoref = Some(mutbl);
+                pick.unsize = if step.unsize {
+                    Some(step.self_ty)
+                } else {
+                    None
+                };
+                pick
             })
-            .nth(0)
+        })
     }
 
     fn pick_method(&mut self, self_ty: Ty<'tcx>) -> Option<PickResult<'tcx>> {
@@ -1177,7 +902,10 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
                            possibly_unsatisfied_predicates: &mut Vec<TraitRef<'tcx>>)
                            -> Option<PickResult<'tcx>> {
         let mut applicable_candidates: Vec<_> = probes.iter()
-            .filter(|&probe| self.consider_probe(self_ty, probe, possibly_unsatisfied_predicates))
+            .map(|probe| {
+                (probe, self.consider_probe(self_ty, probe, possibly_unsatisfied_predicates))
+            })
+            .filter(|&(_, status)| status != ProbeResult::NoMatch)
             .collect();
 
         debug!("applicable_candidates: {:?}", applicable_candidates);
@@ -1192,18 +920,60 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
         }
 
         if applicable_candidates.len() > 1 {
-            let sources = probes.iter().map(|p| p.to_source()).collect();
+            let sources = probes.iter()
+                .map(|p| self.candidate_source(p, self_ty))
+                .collect();
             return Some(Err(MethodError::Ambiguity(sources)));
         }
 
-        applicable_candidates.pop().map(|probe| Ok(probe.to_unadjusted_pick()))
+        applicable_candidates.pop().map(|(probe, status)| {
+            if status == ProbeResult::Match {
+                Ok(probe.to_unadjusted_pick())
+            } else {
+                Err(MethodError::BadReturnType)
+            }
+        })
+    }
+
+    fn select_trait_candidate(&self, trait_ref: ty::TraitRef<'tcx>)
+                              -> traits::SelectionResult<'tcx, traits::Selection<'tcx>>
+    {
+        let cause = traits::ObligationCause::misc(self.span, self.body_id);
+        let predicate =
+            trait_ref.to_poly_trait_ref().to_poly_trait_predicate();
+        let obligation = traits::Obligation::new(cause, self.param_env, predicate);
+        traits::SelectionContext::new(self).select(&obligation)
+    }
+
+    fn candidate_source(&self, candidate: &Candidate<'tcx>, self_ty: Ty<'tcx>)
+                        -> CandidateSource
+    {
+        match candidate.kind {
+            InherentImplCandidate(..) => ImplSource(candidate.item.container.id()),
+            ObjectCandidate |
+            WhereClauseCandidate(_) => TraitSource(candidate.item.container.id()),
+            TraitCandidate(trait_ref) => self.probe(|_| {
+                let _ = self.at(&ObligationCause::dummy(), self.param_env)
+                    .sup(candidate.xform_self_ty, self_ty);
+                match self.select_trait_candidate(trait_ref) {
+                    Ok(Some(traits::Vtable::VtableImpl(ref impl_data))) => {
+                        // If only a single impl matches, make the error message point
+                        // to that impl.
+                        ImplSource(impl_data.impl_def_id)
+                    }
+                    _ => {
+                        TraitSource(candidate.item.container.id())
+                    }
+                }
+            })
+        }
     }
 
     fn consider_probe(&self,
                       self_ty: Ty<'tcx>,
                       probe: &Candidate<'tcx>,
                       possibly_unsatisfied_predicates: &mut Vec<TraitRef<'tcx>>)
-                      -> bool {
+                      -> ProbeResult {
         debug!("consider_probe: self_ty={:?} probe={:?}", self_ty, probe);
 
         self.probe(|_| {
@@ -1213,60 +983,102 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
                 Ok(InferOk { obligations, value: () }) => obligations,
                 Err(_) => {
                     debug!("--> cannot relate self-types");
-                    return false;
+                    return ProbeResult::NoMatch;
                 }
             };
 
+            let mut result = ProbeResult::Match;
+            let selcx = &mut traits::SelectionContext::new(self);
+            let cause = traits::ObligationCause::misc(self.span, self.body_id);
+
             // If so, impls may carry other conditions (e.g., where
             // clauses) that must be considered. Make sure that those
             // match as well (or at least may match, sometimes we
             // don't have enough information to fully evaluate).
-            let (impl_def_id, substs, ref_obligations) = match probe.kind {
+            let candidate_obligations : Vec<_> = match probe.kind {
                 InherentImplCandidate(ref substs, ref ref_obligations) => {
-                    (probe.item.container.id(), substs, ref_obligations)
-                }
-
-                ExtensionImplCandidate(impl_def_id, ref substs, ref ref_obligations) => {
-                    (impl_def_id, substs, ref_obligations)
+                    // Check whether the impl imposes obligations we have to worry about.
+                    let impl_def_id = probe.item.container.id();
+                    let impl_bounds = self.tcx.predicates_of(impl_def_id);
+                    let impl_bounds = impl_bounds.instantiate(self.tcx, substs);
+                    let traits::Normalized { value: impl_bounds, obligations: norm_obligations } =
+                        traits::normalize(selcx, self.param_env, cause.clone(), &impl_bounds);
+
+                    // Convert the bounds into obligations.
+                    let impl_obligations = traits::predicates_for_generics(
+                        cause.clone(), self.param_env, &impl_bounds);
+
+                    debug!("impl_obligations={:?}", impl_obligations);
+                    impl_obligations.into_iter()
+                        .chain(norm_obligations.into_iter())
+                        .chain(ref_obligations.iter().cloned())
+                        .collect()
                 }
 
                 ObjectCandidate |
-                TraitCandidate |
                 WhereClauseCandidate(..) => {
                     // These have no additional conditions to check.
-                    return true;
+                    vec![]
                 }
-            };
-
-            let selcx = &mut traits::SelectionContext::new(self);
-            let cause = traits::ObligationCause::misc(self.span, self.body_id);
 
-            // Check whether the impl imposes obligations we have to worry about.
-            let impl_bounds = self.tcx.predicates_of(impl_def_id);
-            let impl_bounds = impl_bounds.instantiate(self.tcx, substs);
-            let traits::Normalized { value: impl_bounds, obligations: norm_obligations } =
-                traits::normalize(selcx, self.param_env, cause.clone(), &impl_bounds);
+                TraitCandidate(trait_ref) => {
+                    let predicate = trait_ref.to_predicate();
+                    let obligation =
+                        traits::Obligation::new(cause.clone(), self.param_env, predicate);
+                    if !selcx.evaluate_obligation(&obligation) {
+                        if self.probe(|_| self.select_trait_candidate(trait_ref).is_err()) {
+                            // This candidate's primary obligation doesn't even
+                            // select - don't bother registering anything in
+                            // `potentially_unsatisfied_predicates`.
+                            return ProbeResult::NoMatch;
+                        } else {
+                            // Some nested subobligation of this predicate
+                            // failed.
+                            //
+                            // FIXME: try to find the exact nested subobligation
+                            // and point at it rather than reporting the entire
+                            // trait-ref?
+                            result = ProbeResult::NoMatch;
+                            let trait_ref = self.resolve_type_vars_if_possible(&trait_ref);
+                            possibly_unsatisfied_predicates.push(trait_ref);
+                        }
+                    }
+                    vec![]
+                }
+            };
 
-            // Convert the bounds into obligations.
-            let obligations = traits::predicates_for_generics(cause.clone(),
-                                                              self.param_env,
-                                                              &impl_bounds);
-            debug!("impl_obligations={:?}", obligations);
+            debug!("consider_probe - candidate_obligations={:?} sub_obligations={:?}",
+                   candidate_obligations, sub_obligations);
 
             // Evaluate those obligations to see if they might possibly hold.
-            let mut all_true = true;
-            for o in obligations.iter()
-                .chain(sub_obligations.iter())
-                .chain(norm_obligations.iter())
-                .chain(ref_obligations.iter()) {
-                if !selcx.evaluate_obligation(o) {
-                    all_true = false;
+            for o in candidate_obligations.into_iter().chain(sub_obligations) {
+                let o = self.resolve_type_vars_if_possible(&o);
+                if !selcx.evaluate_obligation(&o) {
+                    result = ProbeResult::NoMatch;
                     if let &ty::Predicate::Trait(ref pred) = &o.predicate {
                         possibly_unsatisfied_predicates.push(pred.0.trait_ref);
                     }
                 }
             }
-            all_true
+
+            if let ProbeResult::Match = result {
+                if let (Some(return_ty), Some(xform_ret_ty)) =
+                    (self.return_type, probe.xform_ret_ty)
+                {
+                    let xform_ret_ty = self.resolve_type_vars_if_possible(&xform_ret_ty);
+                    debug!("comparing return_ty {:?} with xform ret ty {:?}",
+                           return_ty,
+                           probe.xform_ret_ty);
+                    if self.at(&ObligationCause::dummy(), self.param_env)
+                        .sup(return_ty, xform_ret_ty)
+                        .is_err()
+                    {
+                        return ProbeResult::BadReturnType;
+                    }
+                }
+            }
+
+            result
         })
     }
 
@@ -1287,22 +1099,25 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
     ///
     /// Now imagine the receiver is `Vec<_>`. It doesn't really matter at this time which impl we
     /// use, so it's ok to just commit to "using the method from the trait Foo".
-    fn collapse_candidates_to_trait_pick(&self, probes: &[&Candidate<'tcx>]) -> Option<Pick<'tcx>> {
+    fn collapse_candidates_to_trait_pick(&self, probes: &[(&Candidate<'tcx>, ProbeResult)])
+                                         -> Option<Pick<'tcx>>
+    {
         // Do all probes correspond to the same trait?
-        let container = probes[0].item.container;
+        let container = probes[0].0.item.container;
         match container {
             ty::TraitContainer(_) => {}
             ty::ImplContainer(_) => return None,
         }
-        if probes[1..].iter().any(|p| p.item.container != container) {
+        if probes[1..].iter().any(|&(p, _)| p.item.container != container) {
             return None;
         }
 
+        // FIXME: check the return type here somehow.
         // If so, just use this trait and call it a day.
         Some(Pick {
-            item: probes[0].item.clone(),
+            item: probes[0].0.item.clone(),
             kind: TraitPick,
-            import_id: probes[0].import_id,
+            import_id: probes[0].0.import_id,
             autoderefs: 0,
             autoref: None,
             unsize: None,
@@ -1340,23 +1155,23 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
                      item: &ty::AssociatedItem,
                      impl_ty: Ty<'tcx>,
                      substs: &Substs<'tcx>)
-                     -> Ty<'tcx> {
+                     -> (Ty<'tcx>, Option<Ty<'tcx>>) {
         if item.kind == ty::AssociatedKind::Method && self.mode == Mode::MethodCall {
-            self.xform_method_self_ty(item.def_id, impl_ty, substs)
+            let sig = self.xform_method_sig(item.def_id, substs);
+            (sig.inputs()[0], Some(sig.output()))
         } else {
-            impl_ty
+            (impl_ty, None)
         }
     }
 
-    fn xform_method_self_ty(&self,
-                            method: DefId,
-                            impl_ty: Ty<'tcx>,
-                            substs: &Substs<'tcx>)
-                            -> Ty<'tcx> {
-        let self_ty = self.tcx.fn_sig(method).input(0);
-        debug!("xform_self_ty(impl_ty={:?}, self_ty={:?}, substs={:?})",
-               impl_ty,
-               self_ty,
+    fn xform_method_sig(&self,
+                        method: DefId,
+                        substs: &Substs<'tcx>)
+                        -> ty::FnSig<'tcx>
+    {
+        let fn_sig = self.tcx.fn_sig(method);
+        debug!("xform_self_ty(fn_sig={:?}, substs={:?})",
+               fn_sig,
                substs);
 
         assert!(!substs.has_escaping_regions());
@@ -1372,10 +1187,10 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
 
         // Erase any late-bound regions from the method and substitute
         // in the values from the substitution.
-        let xform_self_ty = self.erase_late_bound_regions(&self_ty);
+        let xform_fn_sig = self.erase_late_bound_regions(&fn_sig);
 
         if generics.types.is_empty() && generics.regions.is_empty() {
-            xform_self_ty.subst(self.tcx, substs)
+            xform_fn_sig.subst(self.tcx, substs)
         } else {
             let substs = Substs::for_item(self.tcx, method, |def, _| {
                 let i = def.index as usize;
@@ -1394,22 +1209,22 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
                     self.type_var_for_def(self.span, def, cur_substs)
                 }
             });
-            xform_self_ty.subst(self.tcx, substs)
+            xform_fn_sig.subst(self.tcx, substs)
         }
     }
 
     /// Get the type of an impl and generate substitutions with placeholders.
     fn impl_ty_and_substs(&self, impl_def_id: DefId) -> (Ty<'tcx>, &'tcx Substs<'tcx>) {
-        let impl_ty = self.tcx.type_of(impl_def_id);
-
-        let substs = Substs::for_item(self.tcx,
-                                      impl_def_id,
-                                      |_, _| self.tcx.types.re_erased,
-                                      |_, _| self.next_ty_var(
-                                        TypeVariableOrigin::SubstitutionPlaceholder(
-                                            self.tcx.def_span(impl_def_id))));
+        (self.tcx.type_of(impl_def_id), self.fresh_item_substs(impl_def_id))
+    }
 
-        (impl_ty, substs)
+    fn fresh_item_substs(&self, def_id: DefId) -> &'tcx Substs<'tcx> {
+        Substs::for_item(self.tcx,
+                         def_id,
+                         |_, _| self.tcx.types.re_erased,
+                         |_, _| self.next_ty_var(
+                             TypeVariableOrigin::SubstitutionPlaceholder(
+                                 self.tcx.def_span(def_id))))
     }
 
     /// Replace late-bound-regions bound by `value` with `'static` using
@@ -1438,17 +1253,10 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
 
     /// Find the method with the appropriate name (or return type, as the case may be).
     fn impl_or_trait_item(&self, def_id: DefId) -> Vec<ty::AssociatedItem> {
-        match self.looking_for {
-            LookingFor::MethodName(name) => {
-                self.fcx.associated_item(def_id, name).map_or(Vec::new(), |x| vec![x])
-            }
-            LookingFor::ReturnType(return_ty) => {
-                self.tcx
-                    .associated_items(def_id)
-                    .map(|did| self.tcx.associated_item(did.def_id))
-                    .filter(|m| self.matches_return_type(m, return_ty))
-                    .collect()
-            }
+        if let Some(name) = self.method_name {
+            self.fcx.associated_item(def_id, name).map_or(Vec::new(), |x| vec![x])
+        } else {
+            self.tcx.associated_items(def_id).collect()
         }
     }
 }
@@ -1459,9 +1267,8 @@ impl<'tcx> Candidate<'tcx> {
             item: self.item.clone(),
             kind: match self.kind {
                 InherentImplCandidate(..) => InherentImplPick,
-                ExtensionImplCandidate(def_id, ..) => ExtensionImplPick(def_id),
                 ObjectCandidate => ObjectPick,
-                TraitCandidate => TraitPick,
+                TraitCandidate(_) => TraitPick,
                 WhereClauseCandidate(ref trait_ref) => {
                     // Only trait derived from where-clauses should
                     // appear here, so they should not contain any
@@ -1479,14 +1286,4 @@ impl<'tcx> Candidate<'tcx> {
             unsize: None,
         }
     }
-
-    fn to_source(&self) -> CandidateSource {
-        match self.kind {
-            InherentImplCandidate(..) => ImplSource(self.item.container.id()),
-            ExtensionImplCandidate(def_id, ..) => ImplSource(def_id),
-            ObjectCandidate |
-            TraitCandidate |
-            WhereClauseCandidate(_) => TraitSource(self.item.container.id()),
-        }
-    }
 }
diff --git a/src/librustc_typeck/check/method/suggest.rs b/src/librustc_typeck/check/method/suggest.rs
index c8b828f3a434d..f2d7842e473f6 100644
--- a/src/librustc_typeck/check/method/suggest.rs
+++ b/src/librustc_typeck/check/method/suggest.rs
@@ -296,22 +296,6 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                 err.emit();
             }
 
-            MethodError::ClosureAmbiguity(trait_def_id) => {
-                let msg = format!("the `{}` method from the `{}` trait cannot be explicitly \
-                                   invoked on this closure as we have not yet inferred what \
-                                   kind of closure it is",
-                                  item_name,
-                                  self.tcx.item_path_str(trait_def_id));
-                let msg = if let Some(callee) = rcvr_expr {
-                    format!("{}; use overloaded call notation instead (e.g., `{}()`)",
-                            msg,
-                            self.tcx.hir.node_to_pretty_string(callee.id))
-                } else {
-                    msg
-                };
-                self.sess().span_err(span, &msg);
-            }
-
             MethodError::PrivateMatch(def, out_of_scope_traits) => {
                 let mut err = struct_span_err!(self.tcx.sess, span, E0624,
                                                "{} `{}` is private", def.kind_name(), item_name);
@@ -337,6 +321,10 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                 }
                 err.emit();
             }
+
+            MethodError::BadReturnType => {
+                bug!("no return type expectations but got BadReturnType")
+            }
         }
     }
 
diff --git a/src/librustc_typeck/check/mod.rs b/src/librustc_typeck/check/mod.rs
index 955171203e13a..3f210ea1737b7 100644
--- a/src/librustc_typeck/check/mod.rs
+++ b/src/librustc_typeck/check/mod.rs
@@ -85,13 +85,12 @@ use self::method::MethodCallee;
 use self::TupleArgumentsFlag::*;
 
 use astconv::AstConv;
-use fmt_macros::{Parser, Piece, Position};
 use hir::def::{Def, CtorKind};
 use hir::def_id::{CrateNum, DefId, LOCAL_CRATE};
 use rustc_back::slice::ref_slice;
 use rustc::infer::{self, InferCtxt, InferOk, RegionVariableOrigin};
 use rustc::infer::type_variable::{TypeVariableOrigin};
-use rustc::middle::region::CodeExtent;
+use rustc::middle::region;
 use rustc::ty::subst::{Kind, Subst, Substs};
 use rustc::traits::{self, FulfillmentContext, ObligationCause, ObligationCauseCode};
 use rustc::ty::{ParamTy, LvaluePreference, NoPreference, PreferMutLvalue};
@@ -146,6 +145,7 @@ mod cast;
 mod closure;
 mod callee;
 mod compare_method;
+mod generator_interior;
 mod intrinsic;
 mod op;
 
@@ -205,6 +205,8 @@ pub struct Inherited<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
 
     deferred_cast_checks: RefCell<Vec<cast::CastCheck<'tcx>>>,
 
+    deferred_generator_interiors: RefCell<Vec<(hir::BodyId, Ty<'tcx>)>>,
+
     // Anonymized types found in explicit return types and their
     // associated fresh inference variable. Writeback resolves these
     // variables to get the concrete type, which can be used to
@@ -503,6 +505,8 @@ pub struct FnCtxt<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
 
     ret_coercion: Option<RefCell<DynamicCoerceMany<'gcx, 'tcx>>>,
 
+    yield_ty: Option<Ty<'tcx>>,
+
     ps: RefCell<UnsafetyState>,
 
     /// Whether the last checked node generates a divergence (e.g.,
@@ -601,8 +605,9 @@ impl<'a, 'gcx, 'tcx> Inherited<'a, 'gcx, 'tcx> {
         let tcx = infcx.tcx;
         let item_id = tcx.hir.as_local_node_id(def_id);
         let body_id = item_id.and_then(|id| tcx.hir.maybe_body_owned_by(id));
-        let implicit_region_bound = body_id.map(|body| {
-            tcx.mk_region(ty::ReScope(CodeExtent::CallSiteScope(body)))
+        let implicit_region_bound = body_id.map(|body_id| {
+            let body = tcx.hir.body(body_id);
+            tcx.mk_region(ty::ReScope(region::Scope::CallSite(body.value.hir_id.local_id)))
         });
 
         Inherited {
@@ -614,6 +619,7 @@ impl<'a, 'gcx, 'tcx> Inherited<'a, 'gcx, 'tcx> {
             locals: RefCell::new(NodeMap()),
             deferred_call_resolutions: RefCell::new(DefIdMap()),
             deferred_cast_checks: RefCell::new(Vec::new()),
+            deferred_generator_interiors: RefCell::new(Vec::new()),
             anon_types: RefCell::new(NodeMap()),
             implicit_region_bound,
             body_id,
@@ -734,11 +740,20 @@ pub fn provide(providers: &mut Providers) {
         typeck_tables_of,
         has_typeck_tables,
         closure_kind,
+        generator_sig,
         adt_destructor,
         ..*providers
     };
 }
 
+fn generator_sig<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
+                          def_id: DefId)
+                          -> Option<ty::PolyGenSig<'tcx>> {
+    let node_id = tcx.hir.as_local_node_id(def_id).unwrap();
+    let hir_id = tcx.hir.node_to_hir_id(node_id);
+    tcx.typeck_tables_of(def_id).generator_sigs()[hir_id].map(|s| ty::Binder(s))
+}
+
 fn closure_kind<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                           def_id: DefId)
                           -> ty::ClosureKind {
@@ -865,7 +880,7 @@ fn typeck_tables_of<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                                                   param_env,
                                                   &fn_sig);
 
-            check_fn(&inh, param_env, fn_sig, decl, id, body)
+            check_fn(&inh, param_env, fn_sig, decl, id, body, false).0
         } else {
             let fcx = FnCtxt::new(&inh, param_env, body.value.id);
             let expected_type = tcx.type_of(def_id);
@@ -887,6 +902,7 @@ fn typeck_tables_of<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
         fcx.closure_analyze(body);
         fcx.select_obligations_where_possible();
         fcx.check_casts();
+        fcx.resolve_generator_interiors(def_id);
         fcx.select_all_obligations_or_error();
 
         if fn_decl.is_some() {
@@ -986,8 +1002,9 @@ fn check_fn<'a, 'gcx, 'tcx>(inherited: &'a Inherited<'a, 'gcx, 'tcx>,
                             fn_sig: ty::FnSig<'tcx>,
                             decl: &'gcx hir::FnDecl,
                             fn_id: ast::NodeId,
-                            body: &'gcx hir::Body)
-                            -> FnCtxt<'a, 'gcx, 'tcx>
+                            body: &'gcx hir::Body,
+                            can_be_generator: bool)
+                            -> (FnCtxt<'a, 'gcx, 'tcx>, Option<ty::GeneratorInterior<'tcx>>)
 {
     let mut fn_sig = fn_sig.clone();
 
@@ -1010,6 +1027,12 @@ fn check_fn<'a, 'gcx, 'tcx>(inherited: &'a Inherited<'a, 'gcx, 'tcx>,
         fn_sig.abi
     );
 
+    let span = body.value.span;
+
+    if body.is_generator && can_be_generator {
+        fcx.yield_ty = Some(fcx.next_ty_var(TypeVariableOrigin::TypeInference(span)));
+    }
+
     GatherLocalsVisitor { fcx: &fcx, }.visit_body(body);
 
     // Add formal parameters.
@@ -1029,6 +1052,24 @@ fn check_fn<'a, 'gcx, 'tcx>(inherited: &'a Inherited<'a, 'gcx, 'tcx>,
     }
 
     let fn_hir_id = fcx.tcx.hir.node_to_hir_id(fn_id);
+    let gen_ty = if can_be_generator && body.is_generator {
+        let gen_sig = ty::GenSig {
+            yield_ty: fcx.yield_ty.unwrap(),
+            return_ty: ret_ty,
+        };
+        inherited.tables.borrow_mut().generator_sigs_mut().insert(fn_hir_id, Some(gen_sig));
+
+        let witness = fcx.next_ty_var(TypeVariableOrigin::MiscVariable(span));
+        fcx.deferred_generator_interiors.borrow_mut().push((body.id(), witness));
+        let interior = ty::GeneratorInterior::new(witness);
+
+        inherited.tables.borrow_mut().generator_interiors_mut().insert(fn_hir_id, interior);
+
+        Some(interior)
+    } else {
+        inherited.tables.borrow_mut().generator_sigs_mut().insert(fn_hir_id, None);
+        None
+    };
     inherited.tables.borrow_mut().liberated_fn_sigs_mut().insert(fn_hir_id, fn_sig);
 
     fcx.check_return_expr(&body.value);
@@ -1060,11 +1101,11 @@ fn check_fn<'a, 'gcx, 'tcx>(inherited: &'a Inherited<'a, 'gcx, 'tcx>,
     let mut actual_return_ty = coercion.complete(&fcx);
     if actual_return_ty.is_never() {
         actual_return_ty = fcx.next_diverging_ty_var(
-            TypeVariableOrigin::DivergingFn(body.value.span));
+            TypeVariableOrigin::DivergingFn(span));
     }
-    fcx.demand_suptype(body.value.span, ret_ty, actual_return_ty);
+    fcx.demand_suptype(span, ret_ty, actual_return_ty);
 
-    fcx
+    (fcx, gen_ty)
 }
 
 fn check_struct<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
@@ -1173,55 +1214,11 @@ pub fn check_item_type<'a,'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, it: &'tcx hir::Item
 }
 
 fn check_on_unimplemented<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
-                                    def_id: DefId,
+                                    trait_def_id: DefId,
                                     item: &hir::Item) {
-    let generics = tcx.generics_of(def_id);
-    if let Some(ref attr) = item.attrs.iter().find(|a| {
-        a.check_name("rustc_on_unimplemented")
-    }) {
-        if let Some(istring) = attr.value_str() {
-            let istring = istring.as_str();
-            let name = tcx.item_name(def_id).as_str();
-            let parser = Parser::new(&istring);
-            let types = &generics.types;
-            for token in parser {
-                match token {
-                    Piece::String(_) => (), // Normal string, no need to check it
-                    Piece::NextArgument(a) => match a.position {
-                        // `{Self}` is allowed
-                        Position::ArgumentNamed(s) if s == "Self" => (),
-                        // `{ThisTraitsName}` is allowed
-                        Position::ArgumentNamed(s) if s == name => (),
-                        // So is `{A}` if A is a type parameter
-                        Position::ArgumentNamed(s) => match types.iter().find(|t| {
-                            t.name == s
-                        }) {
-                            Some(_) => (),
-                            None => {
-                                span_err!(tcx.sess, attr.span, E0230,
-                                                 "there is no type parameter \
-                                                          {} on trait {}",
-                                                           s, name);
-                            }
-                        },
-                        // `{:1}` and `{}` are not to be used
-                        Position::ArgumentIs(_) => {
-                            span_err!(tcx.sess, attr.span, E0231,
-                                                  "only named substitution \
-                                                   parameters are allowed");
-                        }
-                    }
-                }
-            }
-        } else {
-            struct_span_err!(
-                tcx.sess, attr.span, E0232,
-                "this attribute must have a value")
-                .span_label(attr.span, "attribute requires a value")
-                .note(&format!("eg `#[rustc_on_unimplemented = \"foo\"]`"))
-                .emit();
-        }
-    }
+    let item_def_id = tcx.hir.local_def_id(item.id);
+    // an error would be reported if this fails.
+    let _ = traits::OnUnimplementedDirective::of_item(tcx, trait_def_id, item_def_id);
 }
 
 fn report_forbidden_specialization<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
@@ -1700,6 +1697,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
             param_env,
             err_count_on_creation: inh.tcx.sess.err_count(),
             ret_coercion: None,
+            yield_ty: None,
             ps: RefCell::new(UnsafetyState::function(hir::Unsafety::Normal,
                                                      ast::CRATE_NODE_ID)),
             diverges: Cell::new(Diverges::Maybe),
@@ -2089,6 +2087,13 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
         }
     }
 
+    fn resolve_generator_interiors(&self, def_id: DefId) {
+        let mut deferred_generator_interiors = self.deferred_generator_interiors.borrow_mut();
+        for (body_id, witness) in deferred_generator_interiors.drain(..) {
+            generator_interior::resolve_interior(self, def_id, body_id, witness);
+        }
+    }
+
     /// Apply "fallbacks" to some types
     /// unconstrained types get replaced with ! or  () (depending on whether
     /// feature(never_type) is enabled), unconstrained ints with i32, and
@@ -2423,7 +2428,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
 
         fn parameter_count_error<'tcx>(sess: &Session, sp: Span, expected_count: usize,
                                        arg_count: usize, error_code: &str, variadic: bool,
-                                       def_span: Option<Span>) {
+                                       def_span: Option<Span>, sugg_unit: bool) {
             let mut err = sess.struct_span_err_with_code(sp,
                 &format!("this function takes {}{} parameter{} but {} parameter{} supplied",
                     if variadic {"at least "} else {""},
@@ -2433,13 +2438,23 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                     if arg_count == 1 {" was"} else {"s were"}),
                 error_code);
 
-            err.span_label(sp, format!("expected {}{} parameter{}",
-                                        if variadic {"at least "} else {""},
-                                        expected_count,
-                                        if expected_count == 1 {""} else {"s"}));
             if let Some(def_s) = def_span {
                 err.span_label(def_s, "defined here");
             }
+            if sugg_unit {
+                let sugg_span = sp.end_point();
+                // remove closing `)` from the span
+                let sugg_span = sugg_span.with_hi(sugg_span.lo());
+                err.span_suggestion(
+                    sugg_span,
+                    "expected the unit value `()`. You can create one with a pair of parenthesis",
+                    String::from("()"));
+            } else {
+                err.span_label(sp, format!("expected {}{} parameter{}",
+                                            if variadic {"at least "} else {""},
+                                            expected_count,
+                                            if expected_count == 1 {""} else {"s"}));
+            }
             err.emit();
         }
 
@@ -2448,7 +2463,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
             match tuple_type.sty {
                 ty::TyTuple(arg_types, _) if arg_types.len() != args.len() => {
                     parameter_count_error(tcx.sess, sp_args, arg_types.len(), args.len(),
-                                          "E0057", false, def_span);
+                                          "E0057", false, def_span, false);
                     expected_arg_tys = &[];
                     self.err_args(args.len())
                 }
@@ -2477,13 +2492,21 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                 fn_inputs.to_vec()
             } else {
                 parameter_count_error(tcx.sess, sp_args, expected_arg_count,
-                                      supplied_arg_count, "E0060", true, def_span);
+                                      supplied_arg_count, "E0060", true, def_span, false);
                 expected_arg_tys = &[];
                 self.err_args(supplied_arg_count)
             }
         } else {
+            // is the missing argument of type `()`?
+            let sugg_unit = if expected_arg_tys.len() == 1 && supplied_arg_count == 0 {
+                self.resolve_type_vars_if_possible(&expected_arg_tys[0]).is_nil()
+            } else if fn_inputs.len() == 1 && supplied_arg_count == 0 {
+                self.resolve_type_vars_if_possible(&fn_inputs[0]).is_nil()
+            } else {
+                false
+            };
             parameter_count_error(tcx.sess, sp_args, expected_arg_count,
-                                  supplied_arg_count, "E0061", false, def_span);
+                                  supplied_arg_count, "E0061", false, def_span, sugg_unit);
             expected_arg_tys = &[];
             self.err_args(supplied_arg_count)
         };
@@ -2751,6 +2774,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                                            formal_ret: Ty<'tcx>,
                                            formal_args: &[Ty<'tcx>])
                                            -> Vec<Ty<'tcx>> {
+        let formal_ret = self.resolve_type_vars_with_obligations(formal_ret);
         let expected_args = expected_ret.only_has_type(self).and_then(|ret_ty| {
             self.fudge_regions_if_ok(&RegionVariableOrigin::Coercion(call_span), || {
                 // Attempt to apply a subtyping relationship between the formal
@@ -3070,7 +3094,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                     debug!("tuple struct named {:?}",  base_t);
                     let ident = ast::Ident {
                         name: Symbol::intern(&idx.node.to_string()),
-                        ctxt: idx.span.ctxt.modern(),
+                        ctxt: idx.span.ctxt().modern(),
                     };
                     let (ident, def_scope) =
                         self.tcx.adjust_ident(ident, base_def.did, self.body_id);
@@ -3114,8 +3138,8 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
 
         if tuple_like {
             type_error_struct!(self.tcx().sess, expr.span, expr_t, E0612,
-                               "attempted out-of-bounds tuple index `{}` on type `{}`",
-                               idx.node, expr_t).emit();
+                "attempted out-of-bounds tuple index `{}` on type `{}`",
+                idx.node, expr_t).emit();
         } else {
             self.no_such_field_err(expr.span, idx.node, expr_t).emit();
         }
@@ -3193,7 +3217,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
 
         let adt_ty_hint =
             self.expected_inputs_for_expected_output(span, expected, adt_ty, &[adt_ty])
-            .get(0).cloned().unwrap_or(adt_ty);
+                .get(0).cloned().unwrap_or(adt_ty);
         // re-link the regions that EIfEO can erase.
         self.demand_eqtype(span, adt_ty_hint, adt_ty);
 
@@ -3231,10 +3255,10 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                 error_happened = true;
                 if let Some(_) = variant.find_field_named(field.name.node) {
                     let mut err = struct_span_err!(self.tcx.sess,
-                                                   field.name.span,
-                                                   E0062,
-                                                   "field `{}` specified more than once",
-                                                   field.name.node);
+                                                field.name.span,
+                                                E0062,
+                                                "field `{}` specified more than once",
+                                                field.name.node);
 
                     err.span_label(field.name.span, "used more than once");
 
@@ -3287,10 +3311,10 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                              remaining_fields_names,
                              truncated_fields_error,
                              adt_ty)
-                            .span_label(span, format!("missing {}{}",
-                                        remaining_fields_names,
-                                        truncated_fields_error))
-                            .emit();
+                .span_label(span, format!("missing {}{}",
+                                          remaining_fields_names,
+                                          truncated_fields_error))
+                .emit();
         }
     }
 
@@ -3725,13 +3749,10 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                     // Only check this if not in an `if` condition, as the
                     // mistyped comparison help is more appropriate.
                     if !self.tcx.expr_is_lval(&lhs) {
-                        struct_span_err!(
-                            self.tcx.sess, expr.span, E0070,
-                            "invalid left-hand side expression")
-                        .span_label(
-                            expr.span,
-                            "left-hand of expression not valid")
-                        .emit();
+                        struct_span_err!(self.tcx.sess, expr.span, E0070,
+                                         "invalid left-hand side expression")
+                            .span_label(expr.span, "left-hand of expression not valid")
+                            .emit();
                     }
                 }
             }
@@ -3806,7 +3827,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
           hir::ExprMatch(ref discrim, ref arms, match_src) => {
             self.check_match(expr, &discrim, arms, expected, match_src)
           }
-          hir::ExprClosure(capture, ref decl, body_id, _) => {
+          hir::ExprClosure(capture, ref decl, body_id, _, _) => {
               self.check_expr_closure(expr, capture, &decl, body_id, expected)
           }
           hir::ExprBlock(ref body) => {
@@ -3914,6 +3935,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
           }
           hir::ExprTup(ref elts) => {
             let flds = expected.only_has_type(self).and_then(|ty| {
+                let ty = self.resolve_type_vars_with_obligations(ty);
                 match ty.sty {
                     ty::TyTuple(ref flds, _) => Some(&flds[..]),
                     _ => None
@@ -3997,6 +4019,18 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                   }
               }
            }
+          hir::ExprYield(ref value) => {
+            match self.yield_ty {
+                Some(ty) => {
+                    self.check_expr_coercable_to_type(&value, ty);
+                }
+                None => {
+                    struct_span_err!(self.tcx.sess, expr.span, E0627,
+                                 "yield statement outside of generator literal").emit();
+                }
+            }
+            tcx.mk_nil()
+          }
         }
     }
 
@@ -4448,11 +4482,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
             return;
         }
         let original_span = original_sp(last_stmt.span, blk.span);
-        let span_semi = Span {
-            lo: original_span.hi - BytePos(1),
-            hi: original_span.hi,
-            ctxt: original_span.ctxt,
-        };
+        let span_semi = original_span.with_lo(original_span.hi() - BytePos(1));
         err.span_suggestion(span_semi, "consider removing this semicolon", "".to_string());
     }
 
diff --git a/src/librustc_typeck/check/regionck.rs b/src/librustc_typeck/check/regionck.rs
index fdbdf925e4cfe..d475c37ed8c94 100644
--- a/src/librustc_typeck/check/regionck.rs
+++ b/src/librustc_typeck/check/regionck.rs
@@ -87,7 +87,7 @@ use check::FnCtxt;
 use middle::free_region::FreeRegionMap;
 use middle::mem_categorization as mc;
 use middle::mem_categorization::Categorization;
-use middle::region::{CodeExtent, RegionMaps};
+use middle::region;
 use rustc::hir::def_id::DefId;
 use rustc::ty::subst::Substs;
 use rustc::traits;
@@ -179,7 +179,7 @@ pub struct RegionCtxt<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
 
     region_bound_pairs: Vec<(ty::Region<'tcx>, GenericKind<'tcx>)>,
 
-    pub region_maps: Rc<RegionMaps>,
+    pub region_scope_tree: Rc<region::ScopeTree>,
 
     free_region_map: FreeRegionMap<'tcx>,
 
@@ -187,7 +187,7 @@ pub struct RegionCtxt<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
     body_id: ast::NodeId,
 
     // call_site scope of innermost fn
-    call_site_scope: Option<CodeExtent>,
+    call_site_scope: Option<region::Scope>,
 
     // id of innermost fn or loop
     repeating_scope: ast::NodeId,
@@ -230,10 +230,10 @@ impl<'a, 'gcx, 'tcx> RegionCtxt<'a, 'gcx, 'tcx> {
                RepeatingScope(initial_repeating_scope): RepeatingScope,
                initial_body_id: ast::NodeId,
                Subject(subject): Subject) -> RegionCtxt<'a, 'gcx, 'tcx> {
-        let region_maps = fcx.tcx.region_maps(subject);
+        let region_scope_tree = fcx.tcx.region_scope_tree(subject);
         RegionCtxt {
             fcx,
-            region_maps,
+            region_scope_tree,
             repeating_scope: initial_repeating_scope,
             body_id: initial_body_id,
             call_site_scope: None,
@@ -243,8 +243,8 @@ impl<'a, 'gcx, 'tcx> RegionCtxt<'a, 'gcx, 'tcx> {
         }
     }
 
-    fn set_call_site_scope(&mut self, call_site_scope: Option<CodeExtent>)
-                           -> Option<CodeExtent> {
+    fn set_call_site_scope(&mut self, call_site_scope: Option<region::Scope>)
+                           -> Option<region::Scope> {
         mem::replace(&mut self.call_site_scope, call_site_scope)
     }
 
@@ -305,7 +305,7 @@ impl<'a, 'gcx, 'tcx> RegionCtxt<'a, 'gcx, 'tcx> {
 
         let body_id = body.id();
 
-        let call_site = CodeExtent::CallSiteScope(body_id);
+        let call_site = region::Scope::CallSite(body.value.hir_id.local_id);
         let old_call_site_scope = self.set_call_site_scope(Some(call_site));
 
         let fn_sig = {
@@ -330,7 +330,7 @@ impl<'a, 'gcx, 'tcx> RegionCtxt<'a, 'gcx, 'tcx> {
 
         let old_body_id = self.set_body_id(body_id.node_id);
         self.relate_free_regions(&fn_sig_tys[..], body_id.node_id, span);
-        self.link_fn_args(CodeExtent::Misc(body_id.node_id), &body.arguments);
+        self.link_fn_args(region::Scope::Node(body.value.hir_id.local_id), &body.arguments);
         self.visit_body(body);
         self.visit_region_obligations(body_id.node_id);
 
@@ -580,7 +580,7 @@ impl<'a, 'gcx, 'tcx> RegionCtxt<'a, 'gcx, 'tcx> {
 
     fn resolve_regions_and_report_errors(&self) {
         self.fcx.resolve_regions_and_report_errors(self.subject_def_id,
-                                                   &self.region_maps,
+                                                   &self.region_scope_tree,
                                                    &self.free_region_map);
     }
 
@@ -610,11 +610,11 @@ impl<'a, 'gcx, 'tcx> RegionCtxt<'a, 'gcx, 'tcx> {
             // that the lifetime of any regions that appear in a
             // variable's type enclose at least the variable's scope.
 
-            let var_scope = self.region_maps.var_scope(id);
+            let hir_id = self.tcx.hir.node_to_hir_id(id);
+            let var_scope = self.region_scope_tree.var_scope(hir_id.local_id);
             let var_region = self.tcx.mk_region(ty::ReScope(var_scope));
 
             let origin = infer::BindingTypeIsNotValidAtDecl(span);
-            let hir_id = self.tcx.hir.node_to_hir_id(id);
             self.type_of_node_must_outlive(origin, hir_id, var_region);
 
             let typ = self.resolve_node_type(hir_id);
@@ -668,7 +668,8 @@ impl<'a, 'gcx, 'tcx> Visitor<'gcx> for RegionCtxt<'a, 'gcx, 'tcx> {
         // scope of that expression. This also guarantees basic WF.
         let expr_ty = self.resolve_node_type(expr.hir_id);
         // the region corresponding to this expression
-        let expr_region = self.tcx.node_scope_region(expr.id);
+        let expr_region = self.tcx.mk_region(ty::ReScope(
+            region::Scope::Node(expr.hir_id.local_id)));
         self.type_must_outlive(infer::ExprTypeIsNotInScope(expr_ty, expr.span),
                                expr_ty, expr_region);
 
@@ -825,7 +826,7 @@ impl<'a, 'gcx, 'tcx> Visitor<'gcx> for RegionCtxt<'a, 'gcx, 'tcx> {
                 intravisit::walk_expr(self, expr);
             }
 
-            hir::ExprClosure(.., body_id, _) => {
+            hir::ExprClosure(.., body_id, _, _) => {
                 self.check_expr_fn_block(expr, body_id);
             }
 
@@ -950,7 +951,7 @@ impl<'a, 'gcx, 'tcx> RegionCtxt<'a, 'gcx, 'tcx> {
         // call occurs.
         //
         // FIXME(#6268) to support nested method calls, should be callee_id
-        let callee_scope = CodeExtent::Misc(call_expr.id);
+        let callee_scope = region::Scope::Node(call_expr.hir_id.local_id);
         let callee_region = self.tcx.mk_region(ty::ReScope(callee_scope));
 
         debug!("callee_region={:?}", callee_region);
@@ -979,7 +980,7 @@ impl<'a, 'gcx, 'tcx> RegionCtxt<'a, 'gcx, 'tcx> {
         where F: for<'b> FnOnce(mc::MemCategorizationContext<'b, 'gcx, 'tcx>) -> R
     {
         f(mc::MemCategorizationContext::with_infer(&self.infcx,
-                                                   &self.region_maps,
+                                                   &self.region_scope_tree,
                                                    &self.tables.borrow()))
     }
 
@@ -1002,7 +1003,8 @@ impl<'a, 'gcx, 'tcx> RegionCtxt<'a, 'gcx, 'tcx> {
         // expression.
         self.check_safety_of_rvalue_destructor_if_necessary(cmt.clone(), expr.span);
 
-        let expr_region = self.tcx.node_scope_region(expr.id);
+        let expr_region = self.tcx.mk_region(ty::ReScope(
+            region::Scope::Node(expr.hir_id.local_id)));
         for adjustment in adjustments {
             debug!("constrain_adjustments: adjustment={:?}, cmt={:?}",
                    adjustment, cmt);
@@ -1095,7 +1097,7 @@ impl<'a, 'gcx, 'tcx> RegionCtxt<'a, 'gcx, 'tcx> {
         debug!("constrain_index(index_expr=?, indexed_ty={}",
                self.ty_to_string(indexed_ty));
 
-        let r_index_expr = ty::ReScope(CodeExtent::Misc(index_expr.id));
+        let r_index_expr = ty::ReScope(region::Scope::Node(index_expr.hir_id.local_id));
         if let ty::TyRef(r_ptr, mt) = indexed_ty.sty {
             match mt.ty.sty {
                 ty::TySlice(_) | ty::TyStr => {
@@ -1176,7 +1178,7 @@ impl<'a, 'gcx, 'tcx> RegionCtxt<'a, 'gcx, 'tcx> {
     /// Computes the guarantors for any ref bindings in a match and
     /// then ensures that the lifetime of the resulting pointer is
     /// linked to the lifetime of its guarantor (if any).
-    fn link_fn_args(&self, body_scope: CodeExtent, args: &[hir::Arg]) {
+    fn link_fn_args(&self, body_scope: region::Scope, args: &[hir::Arg]) {
         debug!("regionck::link_fn_args(body_scope={:?})", body_scope);
         for arg in args {
             let arg_ty = self.node_ty(arg.hir_id);
@@ -1232,7 +1234,7 @@ impl<'a, 'gcx, 'tcx> RegionCtxt<'a, 'gcx, 'tcx> {
             }
 
             adjustment::AutoBorrow::RawPtr(m) => {
-                let r = self.tcx.node_scope_region(expr.id);
+                let r = self.tcx.mk_region(ty::ReScope(region::Scope::Node(expr.hir_id.local_id)));
                 self.link_region(expr.span, r, ty::BorrowKind::from_mutbl(m), expr_cmt);
             }
         }
diff --git a/src/librustc_typeck/check/upvar.rs b/src/librustc_typeck/check/upvar.rs
index 6db5c5b1cb0af..82d1210f42b2e 100644
--- a/src/librustc_typeck/check/upvar.rs
+++ b/src/librustc_typeck/check/upvar.rs
@@ -76,10 +76,14 @@ impl<'a, 'gcx, 'tcx> Visitor<'gcx> for InferBorrowKindVisitor<'a, 'gcx, 'tcx> {
 
     fn visit_expr(&mut self, expr: &'gcx hir::Expr) {
         match expr.node {
-            hir::ExprClosure(cc, _, body_id, _) => {
+            hir::ExprClosure(cc, _, body_id, _, is_generator) => {
                 let body = self.fcx.tcx.hir.body(body_id);
                 self.visit_body(body);
-                self.fcx.analyze_closure((expr.id, expr.hir_id), expr.span, body, cc);
+                self.fcx.analyze_closure((expr.id, expr.hir_id),
+                                         expr.span,
+                                         body,
+                                         cc,
+                                         is_generator);
             }
 
             _ => { }
@@ -94,22 +98,27 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                        (closure_node_id, closure_hir_id): (ast::NodeId, hir::HirId),
                        span: Span,
                        body: &hir::Body,
-                       capture_clause: hir::CaptureClause) {
+                       capture_clause: hir::CaptureClause,
+                       gen: bool) {
         /*!
          * Analysis starting point.
          */
 
         debug!("analyze_closure(id={:?}, body.id={:?})", closure_node_id, body.id());
 
-        let infer_kind = match self.tables
-                                   .borrow_mut()
-                                   .closure_kinds_mut()
-                                   .entry(closure_hir_id) {
-            Entry::Occupied(_) => false,
-            Entry::Vacant(entry) => {
-                debug!("check_closure: adding closure {:?} as Fn", closure_node_id);
-                entry.insert((ty::ClosureKind::Fn, None));
-                true
+        let infer_kind = if gen {
+            false
+        } else {
+            match self.tables
+                      .borrow_mut()
+                      .closure_kinds_mut()
+                      .entry(closure_hir_id) {
+                Entry::Occupied(_) => false,
+                Entry::Vacant(entry) => {
+                    debug!("check_closure: adding closure {:?} as Fn", closure_node_id);
+                    entry.insert((ty::ClosureKind::Fn, None));
+                    true
+                }
             }
         };
 
@@ -143,7 +152,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
 
         {
             let body_owner_def_id = self.tcx.hir.body_owner_def_id(body.id());
-            let region_maps = &self.tcx.region_maps(body_owner_def_id);
+            let region_scope_tree = &self.tcx.region_scope_tree(body_owner_def_id);
             let mut delegate = InferBorrowKind {
                 fcx: self,
                 adjust_closure_kinds: FxHashMap(),
@@ -152,7 +161,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
             euv::ExprUseVisitor::with_infer(&mut delegate,
                                             &self.infcx,
                                             self.param_env,
-                                            region_maps,
+                                            region_scope_tree,
                                             &self.tables.borrow())
                 .consume_body(body);
 
@@ -184,7 +193,8 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
 
         // Extract the type variables UV0...UVn.
         let (def_id, closure_substs) = match self.node_ty(closure_hir_id).sty {
-            ty::TyClosure(def_id, substs) => (def_id, substs),
+            ty::TyClosure(def_id, substs) |
+            ty::TyGenerator(def_id, substs, _) => (def_id, substs),
             ref t => {
                 span_bug!(
                     span,
diff --git a/src/librustc_typeck/check/writeback.rs b/src/librustc_typeck/check/writeback.rs
index 36c72fc4b19d6..7810d9049e10e 100644
--- a/src/librustc_typeck/check/writeback.rs
+++ b/src/librustc_typeck/check/writeback.rs
@@ -45,6 +45,8 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
         wbcx.visit_anon_types();
         wbcx.visit_cast_types();
         wbcx.visit_free_region_map();
+        wbcx.visit_generator_sigs();
+        wbcx.visit_generator_interiors();
 
         let used_trait_imports = mem::replace(&mut self.tables.borrow_mut().used_trait_imports,
                                               DefIdSet());
@@ -164,7 +166,7 @@ impl<'cx, 'gcx, 'tcx> Visitor<'gcx> for WritebackCx<'cx, 'gcx, 'tcx> {
 
         self.visit_node_id(e.span, e.hir_id);
 
-        if let hir::ExprClosure(_, _, body, _) = e.node {
+        if let hir::ExprClosure(_, _, body, _, _) = e.node {
             let body = self.fcx.tcx.hir.body(body);
             for arg in &body.arguments {
                 self.visit_node_id(e.span, arg.hir_id);
@@ -357,6 +359,33 @@ impl<'cx, 'gcx, 'tcx> WritebackCx<'cx, 'gcx, 'tcx> {
         }
     }
 
+    fn visit_generator_interiors(&mut self) {
+        let common_local_id_root = self.fcx.tables.borrow().local_id_root.unwrap();
+        for (&id, interior) in self.fcx.tables.borrow().generator_interiors().iter() {
+            let hir_id = hir::HirId {
+                owner: common_local_id_root.index,
+                local_id: id,
+            };
+            let interior = self.resolve(interior, &hir_id);
+            self.tables.generator_interiors_mut().insert(hir_id, interior);
+        }
+    }
+
+    fn visit_generator_sigs(&mut self) {
+        let common_local_id_root = self.fcx.tables.borrow().local_id_root.unwrap();
+        for (&id, gen_sig) in self.fcx.tables.borrow().generator_sigs().iter() {
+            let hir_id = hir::HirId {
+                owner: common_local_id_root.index,
+                local_id: id,
+            };
+            let gen_sig = gen_sig.map(|s| ty::GenSig {
+                yield_ty: self.resolve(&s.yield_ty, &hir_id),
+                return_ty: self.resolve(&s.return_ty, &hir_id),
+            });
+            self.tables.generator_sigs_mut().insert(hir_id, gen_sig);
+        }
+    }
+
     fn visit_liberated_fn_sigs(&mut self) {
         let fcx_tables = self.fcx.tables.borrow();
         debug_assert_eq!(fcx_tables.local_id_root, self.tables.local_id_root);
diff --git a/src/librustc_typeck/coherence/builtin.rs b/src/librustc_typeck/coherence/builtin.rs
index 9305eff143652..b421fdfe8d813 100644
--- a/src/librustc_typeck/coherence/builtin.rs
+++ b/src/librustc_typeck/coherence/builtin.rs
@@ -12,7 +12,7 @@
 //! up data structures required by type-checking/translation.
 
 use rustc::middle::free_region::FreeRegionMap;
-use rustc::middle::region::RegionMaps;
+use rustc::middle::region;
 use rustc::middle::lang_items::UnsizeTraitLangItem;
 
 use rustc::traits::{self, ObligationCause};
@@ -390,10 +390,10 @@ pub fn coerce_unsized_info<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
         }
 
         // Finally, resolve all regions.
-        let region_maps = RegionMaps::new();
+        let region_scope_tree = region::ScopeTree::default();
         let mut free_regions = FreeRegionMap::new();
         free_regions.relate_free_regions_from_predicates(&param_env.caller_bounds);
-        infcx.resolve_regions_and_report_errors(impl_did, &region_maps, &free_regions);
+        infcx.resolve_regions_and_report_errors(impl_did, &region_scope_tree, &free_regions);
 
         CoerceUnsizedInfo {
             custom_kind: kind
diff --git a/src/librustc_typeck/collect.rs b/src/librustc_typeck/collect.rs
index ea86c570c8296..c177623af48fb 100644
--- a/src/librustc_typeck/collect.rs
+++ b/src/librustc_typeck/collect.rs
@@ -1153,7 +1153,12 @@ fn type_of<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 
         NodeField(field) => icx.to_ty(&field.ty),
 
-        NodeExpr(&hir::Expr { node: hir::ExprClosure(..), .. }) => {
+        NodeExpr(&hir::Expr { node: hir::ExprClosure(.., is_generator), .. }) => {
+            if is_generator {
+                let hir_id = tcx.hir.node_to_hir_id(node_id);
+                return tcx.typeck_tables_of(def_id).node_id_to_type(hir_id);
+            }
+
             tcx.mk_closure(def_id, Substs::for_item(
                 tcx, def_id,
                 |def, _| {
diff --git a/src/librustc_typeck/diagnostics.rs b/src/librustc_typeck/diagnostics.rs
index cb430efd9508f..6bbe2233ff1fa 100644
--- a/src/librustc_typeck/diagnostics.rs
+++ b/src/librustc_typeck/diagnostics.rs
@@ -2505,50 +2505,6 @@ fn baz<I>(x: &<I as Foo>::A) where I: Foo<A=Bar> {}
 ```
 "##,
 
-E0230: r##"
-The trait has more type parameters specified than appear in its definition.
-
-Erroneous example code:
-
-```compile_fail,E0230
-#![feature(on_unimplemented)]
-#[rustc_on_unimplemented = "Trait error on `{Self}` with `<{A},{B},{C}>`"]
-// error: there is no type parameter C on trait TraitWithThreeParams
-trait TraitWithThreeParams<A,B>
-{}
-```
-
-Include the correct number of type parameters and the compilation should
-proceed:
-
-```
-#![feature(on_unimplemented)]
-#[rustc_on_unimplemented = "Trait error on `{Self}` with `<{A},{B},{C}>`"]
-trait TraitWithThreeParams<A,B,C> // ok!
-{}
-```
-"##,
-
-E0232: r##"
-The attribute must have a value. Erroneous code example:
-
-```compile_fail,E0232
-#![feature(on_unimplemented)]
-
-#[rustc_on_unimplemented] // error: this attribute must have a value
-trait Bar {}
-```
-
-Please supply the missing value of the attribute. Example:
-
-```
-#![feature(on_unimplemented)]
-
-#[rustc_on_unimplemented = "foo"] // ok!
-trait Bar {}
-```
-"##,
-
 E0243: r##"
 This error indicates that not enough type parameters were found in a type or
 trait.
@@ -4690,7 +4646,6 @@ register_diagnostics! {
     E0224, // at least one non-builtin train is required for an object type
     E0227, // ambiguous lifetime bound, explicit lifetime bound required
     E0228, // explicit lifetime bound required
-    E0231, // only named substitution parameters are allowed
 //  E0233,
 //  E0234,
 //  E0235, // structure constructor specifies a structure of type but
@@ -4721,4 +4676,5 @@ register_diagnostics! {
     E0588, // packed struct cannot transitively contain a `[repr(align)]` struct
     E0592, // duplicate definitions with name `{}`
 //  E0613, // Removed (merged with E0609)
+    E0627, // yield statement outside of generator literal
 }
diff --git a/src/librustc_typeck/lib.rs b/src/librustc_typeck/lib.rs
index 86feea13b1723..7a6ee73b9b9e9 100644
--- a/src/librustc_typeck/lib.rs
+++ b/src/librustc_typeck/lib.rs
@@ -84,7 +84,6 @@ This API is completely unstable and subject to change.
 extern crate syntax_pos;
 
 extern crate arena;
-extern crate fmt_macros;
 #[macro_use] extern crate rustc;
 extern crate rustc_platform_intrinsics as intrinsics;
 extern crate rustc_back;
diff --git a/src/librustc_typeck/variance/constraints.rs b/src/librustc_typeck/variance/constraints.rs
index 40474a7933f80..70b989b6ab21c 100644
--- a/src/librustc_typeck/variance/constraints.rs
+++ b/src/librustc_typeck/variance/constraints.rs
@@ -294,6 +294,7 @@ impl<'a, 'tcx> ConstraintContext<'a, 'tcx> {
             }
 
             ty::TyFnDef(..) |
+            ty::TyGenerator(..) |
             ty::TyClosure(..) => {
                 bug!("Unexpected closure type in variance computation");
             }
diff --git a/src/librustdoc/Cargo.toml b/src/librustdoc/Cargo.toml
index f9400e68a16c5..00050bc357827 100644
--- a/src/librustdoc/Cargo.toml
+++ b/src/librustdoc/Cargo.toml
@@ -12,6 +12,7 @@ path = "lib.rs"
 env_logger = { version = "0.4", default-features = false }
 log = "0.3"
 pulldown-cmark = { version = "0.0.14", default-features = false }
+html-diff = "0.0.4"
 
 [build-dependencies]
 build_helper = { path = "../build_helper" }
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index 7d6ad5286d111..aab44ddce0e6a 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -457,8 +457,8 @@ impl Clean<Item> for doctree::Module {
         // the outer `mod` item for the source code.
         let whence = {
             let cm = cx.sess().codemap();
-            let outer = cm.lookup_char_pos(self.where_outer.lo);
-            let inner = cm.lookup_char_pos(self.where_inner.lo);
+            let outer = cm.lookup_char_pos(self.where_outer.lo());
+            let inner = cm.lookup_char_pos(self.where_inner.lo());
             if outer.file.start_pos == inner.file.start_pos {
                 // mod foo { ... }
                 self.where_outer
@@ -1984,7 +1984,7 @@ impl<'tcx> Clean<Type> for ty::Ty<'tcx> {
                 }).collect())
             }
 
-            ty::TyClosure(..) => Tuple(vec![]), // FIXME(pcwalton)
+            ty::TyClosure(..) | ty::TyGenerator(..) => Tuple(vec![]), // FIXME(pcwalton)
 
             ty::TyInfer(..) => panic!("TyInfer"),
             ty::TyError => panic!("TyError"),
@@ -2251,8 +2251,8 @@ impl Clean<Span> for syntax_pos::Span {
 
         let cm = cx.sess().codemap();
         let filename = cm.span_to_filename(*self);
-        let lo = cm.lookup_char_pos(self.lo);
-        let hi = cm.lookup_char_pos(self.hi);
+        let lo = cm.lookup_char_pos(self.lo());
+        let hi = cm.lookup_char_pos(self.hi());
         Span {
             filename: filename.to_string(),
             loline: lo.line,
diff --git a/src/librustdoc/html/format.rs b/src/librustdoc/html/format.rs
index 988890ffedcdd..10a3878073e97 100644
--- a/src/librustdoc/html/format.rs
+++ b/src/librustdoc/html/format.rs
@@ -228,7 +228,7 @@ impl<'a> fmt::Display for WhereClause<'a> {
         }
 
         if end_newline {
-            //add a space so stripping <br> tags and breaking spaces still renders properly
+            // add a space so stripping <br> tags and breaking spaces still renders properly
             if f.alternate() {
                 clause.push(' ');
             } else {
diff --git a/src/librustdoc/html/highlight.rs b/src/librustdoc/html/highlight.rs
index eb27fa3abfa19..e6b236deac4ee 100644
--- a/src/librustdoc/html/highlight.rs
+++ b/src/librustdoc/html/highlight.rs
@@ -172,6 +172,21 @@ impl<'a> Classifier<'a> {
         }
     }
 
+    /// Gets the next token out of the lexer, emitting fatal errors if lexing fails.
+    fn try_next_token(&mut self) -> io::Result<TokenAndSpan> {
+        match self.lexer.try_next_token() {
+            Ok(tas) => Ok(tas),
+            Err(_) => {
+                self.lexer.emit_fatal_errors();
+                self.lexer.sess.span_diagnostic
+                    .struct_warn("Backing out of syntax highlighting")
+                    .note("You probably did not intend to render this as a rust code-block")
+                    .emit();
+                Err(io::Error::new(io::ErrorKind::Other, ""))
+            }
+        }
+    }
+
     /// Exhausts the `lexer` writing the output into `out`.
     ///
     /// The general structure for this method is to iterate over each token,
@@ -183,18 +198,7 @@ impl<'a> Classifier<'a> {
                                    out: &mut W)
                                    -> io::Result<()> {
         loop {
-            let next = match self.lexer.try_next_token() {
-                Ok(tas) => tas,
-                Err(_) => {
-                    self.lexer.emit_fatal_errors();
-                    self.lexer.sess.span_diagnostic
-                        .struct_warn("Backing out of syntax highlighting")
-                        .note("You probably did not intend to render this as a rust code-block")
-                        .emit();
-                    return Err(io::Error::new(io::ErrorKind::Other, ""));
-                }
-            };
-
+            let next = self.try_next_token()?;
             if next.tok == token::Eof {
                 break;
             }
@@ -255,13 +259,37 @@ impl<'a> Classifier<'a> {
                 }
             }
 
-            // This is the start of an attribute. We're going to want to
+            // This might be the start of an attribute. We're going to want to
             // continue highlighting it as an attribute until the ending ']' is
             // seen, so skip out early. Down below we terminate the attribute
             // span when we see the ']'.
             token::Pound => {
-                self.in_attribute = true;
-                out.enter_span(Class::Attribute)?;
+                // We can't be sure that our # begins an attribute (it could
+                // just be appearing in a macro) until we read either `#![` or
+                // `#[` from the input stream.
+                //
+                // We don't want to start highlighting as an attribute until
+                // we're confident there is going to be a ] coming up, as
+                // otherwise # tokens in macros highlight the rest of the input
+                // as an attribute.
+
+                // Case 1: #![inner_attribute]
+                if self.lexer.peek().tok == token::Not {
+                    self.try_next_token()?; // NOTE: consumes `!` token!
+                    if self.lexer.peek().tok == token::OpenDelim(token::Bracket) {
+                        self.in_attribute = true;
+                        out.enter_span(Class::Attribute)?;
+                    }
+                    out.string("#", Class::None, None)?;
+                    out.string("!", Class::None, None)?;
+                    return Ok(());
+                }
+
+                // Case 2: #[outer_attribute]
+                if self.lexer.peek().tok == token::OpenDelim(token::Bracket) {
+                    self.in_attribute = true;
+                    out.enter_span(Class::Attribute)?;
+                }
                 out.string("#", Class::None, None)?;
                 return Ok(());
             }
diff --git a/src/librustdoc/html/render.rs b/src/librustdoc/html/render.rs
index 5457f69cb6dab..cc84e340c74f8 100644
--- a/src/librustdoc/html/render.rs
+++ b/src/librustdoc/html/render.rs
@@ -63,7 +63,7 @@ use rustc::util::nodemap::{FxHashMap, FxHashSet};
 use rustc::session::config::nightly_options::is_nightly_build;
 use rustc_data_structures::flock;
 
-use clean::{self, AttributesExt, GetDefId, SelfTy, Mutability};
+use clean::{self, AttributesExt, GetDefId, SelfTy, Mutability, Span};
 use doctree;
 use fold::DocFolder;
 use html::escape::Escape;
@@ -75,6 +75,8 @@ use html::item_type::ItemType;
 use html::markdown::{self, Markdown, MarkdownHtml, MarkdownSummaryLine, RenderType};
 use html::{highlight, layout};
 
+use html_diff;
+
 /// A pair of name and its optional document.
 pub type NameDoc = (String, Option<String>);
 
@@ -122,6 +124,9 @@ pub struct SharedContext {
     /// The given user css file which allow to customize the generated
     /// documentation theme.
     pub css_file_extension: Option<PathBuf>,
+    /// Warnings for the user if rendering would differ using different markdown
+    /// parsers.
+    pub markdown_warnings: RefCell<Vec<(Span, String, Vec<html_diff::Difference>)>>,
 }
 
 /// Indicates where an external crate can be found.
@@ -455,6 +460,7 @@ pub fn run(mut krate: clean::Crate,
             krate: krate.name.clone(),
         },
         css_file_extension: css_file_extension.clone(),
+        markdown_warnings: RefCell::new(vec![]),
     };
 
     // If user passed in `--playground-url` arg, we fill in crate name here
@@ -577,8 +583,102 @@ pub fn run(mut krate: clean::Crate,
 
     write_shared(&cx, &krate, &*cache, index)?;
 
+    let scx = cx.shared.clone();
+
     // And finally render the whole crate's documentation
-    cx.krate(krate)
+    let result = cx.krate(krate);
+
+    let markdown_warnings = scx.markdown_warnings.borrow();
+    if !markdown_warnings.is_empty() {
+        println!("WARNING: documentation for this crate may be rendered \
+                  differently using the new Pulldown renderer.");
+        println!("    See https://github.com/rust-lang/rust/issues/44229 for details.");
+        for &(ref span, ref text, ref diffs) in &*markdown_warnings {
+            println!("WARNING: rendering difference in `{}`", concise_str(text));
+            println!("   --> {}:{}:{}", span.filename, span.loline, span.locol);
+            for d in diffs {
+                render_difference(d);
+            }
+        }
+    }
+
+    result
+}
+
+// A short, single-line view of `s`.
+fn concise_str(s: &str) -> String {
+    if s.contains('\n') {
+        return format!("{}...", s.lines().next().expect("Impossible! We just found a newline"));
+    }
+    if s.len() > 70 {
+        return format!("{} ... {}", &s[..50], &s[s.len()-20..]);
+    }
+    s.to_owned()
+}
+
+// Returns short versions of s1 and s2, starting from where the strings differ.
+fn concise_compared_strs(s1: &str, s2: &str) -> (String, String) {
+    let s1 = s1.trim();
+    let s2 = s2.trim();
+    if !s1.contains('\n') && !s2.contains('\n') && s1.len() <= 70 && s2.len() <= 70 {
+        return (s1.to_owned(), s2.to_owned());
+    }
+
+    let mut start_byte = 0;
+    for (c1, c2) in s1.chars().zip(s2.chars()) {
+        if c1 != c2 {
+            break;
+        }
+
+        start_byte += c1.len_utf8();
+    }
+
+    if start_byte == 0 {
+        return (concise_str(s1), concise_str(s2));
+    }
+
+    let s1 = &s1[start_byte..];
+    let s2 = &s2[start_byte..];
+    (format!("...{}", concise_str(s1)), format!("...{}", concise_str(s2)))
+}
+
+fn render_difference(diff: &html_diff::Difference) {
+    match *diff {
+        html_diff::Difference::NodeType { ref elem, ref opposite_elem } => {
+            println!("    {} Types differ: expected: `{}`, found: `{}`",
+                     elem.path, elem.element_name, opposite_elem.element_name);
+        }
+        html_diff::Difference::NodeName { ref elem, ref opposite_elem } => {
+            println!("    {} Tags differ: expected: `{}`, found: `{}`",
+                     elem.path, elem.element_name, opposite_elem.element_name);
+        }
+        html_diff::Difference::NodeAttributes { ref elem,
+                                     ref elem_attributes,
+                                     ref opposite_elem_attributes,
+                                     .. } => {
+            println!("    {} Attributes differ in `{}`: expected: `{:?}`, found: `{:?}`",
+                     elem.path, elem.element_name, elem_attributes, opposite_elem_attributes);
+        }
+        html_diff::Difference::NodeText { ref elem, ref elem_text, ref opposite_elem_text, .. } => {
+            let (s1, s2) = concise_compared_strs(elem_text, opposite_elem_text);
+            println!("    {} Text differs:\n        expected: `{}`\n        found:    `{}`",
+                     elem.path, s1, s2);
+        }
+        html_diff::Difference::NotPresent { ref elem, ref opposite_elem } => {
+            if let Some(ref elem) = *elem {
+                println!("    {} One element is missing: expected: `{}`",
+                         elem.path, elem.element_name);
+            } else if let Some(ref elem) = *opposite_elem {
+                if elem.element_name.is_empty() {
+                    println!("    {} Unexpected element: `{}`",
+                             elem.path, concise_str(&elem.element_content));
+                } else {
+                    println!("    {} Unexpected element `{}`: found: `{}`",
+                             elem.path, elem.element_name, concise_str(&elem.element_content));
+                }
+            }
+        }
+    }
 }
 
 /// Build the search index from the collected metadata
@@ -1523,8 +1623,7 @@ impl<'a> fmt::Display for Item<'a> {
                 } else {
                     write!(fmt, "Module ")?;
                 },
-            clean::FunctionItem(..) | clean::ForeignFunctionItem(..) =>
-                write!(fmt, "Function ")?,
+            clean::FunctionItem(..) | clean::ForeignFunctionItem(..) => write!(fmt, "Function ")?,
             clean::TraitItem(..) => write!(fmt, "Trait ")?,
             clean::StructItem(..) => write!(fmt, "Struct ")?,
             clean::UnionItem(..) => write!(fmt, "Union ")?,
@@ -1532,8 +1631,7 @@ impl<'a> fmt::Display for Item<'a> {
             clean::TypedefItem(..) => write!(fmt, "Type Definition ")?,
             clean::MacroItem(..) => write!(fmt, "Macro ")?,
             clean::PrimitiveItem(..) => write!(fmt, "Primitive Type ")?,
-            clean::StaticItem(..) | clean::ForeignStaticItem(..) =>
-                write!(fmt, "Static ")?,
+            clean::StaticItem(..) | clean::ForeignStaticItem(..) => write!(fmt, "Static ")?,
             clean::ConstantItem(..) => write!(fmt, "Constant ")?,
             _ => {
                 // We don't generate pages for any other type.
@@ -1641,12 +1739,84 @@ fn plain_summary_line(s: Option<&str>) -> String {
 fn document(w: &mut fmt::Formatter, cx: &Context, item: &clean::Item) -> fmt::Result {
     document_stability(w, cx, item)?;
     let prefix = render_assoc_const_value(item);
-    document_full(w, item, cx.render_type, &prefix)?;
+    document_full(w, item, cx, &prefix)?;
     Ok(())
 }
 
+/// Render md_text as markdown. Warns the user if there are difference in
+/// rendering between Pulldown and Hoedown.
+fn render_markdown(w: &mut fmt::Formatter,
+                   md_text: &str,
+                   span: Span,
+                   render_type: RenderType,
+                   prefix: &str,
+                   scx: &SharedContext)
+                   -> fmt::Result {
+    let hoedown_output = format!("{}", Markdown(md_text, RenderType::Hoedown));
+    // We only emit warnings if the user has opted-in to Pulldown rendering.
+    let output = if render_type == RenderType::Pulldown {
+        let pulldown_output = format!("{}", Markdown(md_text, RenderType::Pulldown));
+        let differences = html_diff::get_differences(&pulldown_output, &hoedown_output);
+        let differences = differences.into_iter()
+            .filter(|s| {
+                match *s {
+                    html_diff::Difference::NodeText { ref elem_text,
+                                                      ref opposite_elem_text,
+                                                      .. }
+                        if match_non_whitespace(elem_text, opposite_elem_text) => false,
+                    _ => true,
+                }
+            })
+            .collect::<Vec<_>>();
+
+        if !differences.is_empty() {
+            scx.markdown_warnings.borrow_mut().push((span, md_text.to_owned(), differences));
+        }
+
+        pulldown_output
+    } else {
+        hoedown_output
+    };
+
+    write!(w, "<div class='docblock'>{}{}</div>", prefix, output)
+}
+
+// Returns true iff s1 and s2 match, ignoring whitespace.
+fn match_non_whitespace(s1: &str, s2: &str) -> bool {
+    let s1 = s1.trim();
+    let s2 = s2.trim();
+    let mut cs1 = s1.chars();
+    let mut cs2 = s2.chars();
+    while let Some(c1) = cs1.next() {
+        if c1.is_whitespace() {
+            continue;
+        }
+
+        loop {
+            if let Some(c2) = cs2.next() {
+                if !c2.is_whitespace() {
+                    if c1 != c2 {
+                        return false;
+                    }
+                    break;
+                }
+            } else {
+                return false;
+            }
+        }
+    }
+
+    while let Some(c2) = cs2.next() {
+        if !c2.is_whitespace() {
+            return false;
+        }
+    }
+
+    true
+}
+
 fn document_short(w: &mut fmt::Formatter, item: &clean::Item, link: AssocItemLink,
-                  render_type: RenderType, prefix: &str) -> fmt::Result {
+                  cx: &Context, prefix: &str) -> fmt::Result {
     if let Some(s) = item.doc_value() {
         let markdown = if s.contains('\n') {
             format!("{} [Read more]({})",
@@ -1654,7 +1824,7 @@ fn document_short(w: &mut fmt::Formatter, item: &clean::Item, link: AssocItemLin
         } else {
             format!("{}", &plain_summary_line(Some(s)))
         };
-        write!(w, "<div class='docblock'>{}{}</div>", prefix, Markdown(&markdown, render_type))?;
+        render_markdown(w, &markdown, item.source.clone(), cx.render_type, prefix, &cx.shared)?;
     } else if !prefix.is_empty() {
         write!(w, "<div class='docblock'>{}</div>", prefix)?;
     }
@@ -1676,9 +1846,9 @@ fn render_assoc_const_value(item: &clean::Item) -> String {
 }
 
 fn document_full(w: &mut fmt::Formatter, item: &clean::Item,
-                 render_type: RenderType, prefix: &str) -> fmt::Result {
+                 cx: &Context, prefix: &str) -> fmt::Result {
     if let Some(s) = item.doc_value() {
-        write!(w, "<div class='docblock'>{}{}</div>", prefix, Markdown(s, render_type))?;
+        render_markdown(w, s, item.source.clone(), cx.render_type, prefix, &cx.shared)?;
     } else if !prefix.is_empty() {
         write!(w, "<div class='docblock'>{}</div>", prefix)?;
     }
@@ -3077,20 +3247,20 @@ fn render_impl(w: &mut fmt::Formatter, cx: &Context, i: &Impl, link: AssocItemLi
                         // because impls can't have a stability.
                         document_stability(w, cx, it)?;
                         if item.doc_value().is_some() {
-                            document_full(w, item, cx.render_type, &prefix)?;
+                            document_full(w, item, cx, &prefix)?;
                         } else {
                             // In case the item isn't documented,
                             // provide short documentation from the trait.
-                            document_short(w, it, link, cx.render_type, &prefix)?;
+                            document_short(w, it, link, cx, &prefix)?;
                         }
                     }
                 } else {
                     document_stability(w, cx, item)?;
-                    document_full(w, item, cx.render_type, &prefix)?;
+                    document_full(w, item, cx, &prefix)?;
                 }
             } else {
                 document_stability(w, cx, item)?;
-                document_short(w, item, link, cx.render_type, &prefix)?;
+                document_short(w, item, link, cx, &prefix)?;
             }
         }
         Ok(())
@@ -3559,3 +3729,35 @@ fn test_name_sorting() {
     sorted.sort_by_key(|&s| name_key(s));
     assert_eq!(names, sorted);
 }
+
+#[cfg(test)]
+#[test]
+fn test_match_non_whitespace() {
+    assert!(match_non_whitespace("", ""));
+    assert!(match_non_whitespace("  ", ""));
+    assert!(match_non_whitespace("", "  "));
+
+    assert!(match_non_whitespace("a", "a"));
+    assert!(match_non_whitespace(" a ", "a"));
+    assert!(match_non_whitespace("a", "  a"));
+    assert!(match_non_whitespace("abc", "abc"));
+    assert!(match_non_whitespace("abc", " abc "));
+    assert!(match_non_whitespace("abc  ", "abc"));
+    assert!(match_non_whitespace("abc xyz", "abc xyz"));
+    assert!(match_non_whitespace("abc xyz", "abc\nxyz"));
+    assert!(match_non_whitespace("abc xyz", "abcxyz"));
+    assert!(match_non_whitespace("abcxyz", "abc xyz"));
+    assert!(match_non_whitespace("abc    xyz ", " abc xyz\n"));
+
+    assert!(!match_non_whitespace("a", "b"));
+    assert!(!match_non_whitespace(" a ", "c"));
+    assert!(!match_non_whitespace("a", "  aa"));
+    assert!(!match_non_whitespace("abc", "ac"));
+    assert!(!match_non_whitespace("abc", " adc "));
+    assert!(!match_non_whitespace("abc  ", "abca"));
+    assert!(!match_non_whitespace("abc xyz", "abc xy"));
+    assert!(!match_non_whitespace("abc xyz", "bc\nxyz"));
+    assert!(!match_non_whitespace("abc xyz", "abc.xyz"));
+    assert!(!match_non_whitespace("abcxyz", "abc.xyz"));
+    assert!(!match_non_whitespace("abc    xyz ", " abc xyz w"));
+}
diff --git a/src/librustdoc/html/static/rustdoc.css b/src/librustdoc/html/static/rustdoc.css
index 4a3286b421ae9..ca55d0e5d2a8e 100644
--- a/src/librustdoc/html/static/rustdoc.css
+++ b/src/librustdoc/html/static/rustdoc.css
@@ -329,6 +329,10 @@ h4 > code, h3 > code, .invisible > code {
 	display: inline-block;
 }
 
+.in-band > code {
+	display: inline-block;
+}
+
 #main { position: relative; }
 #main > .since {
 	top: inherit;
@@ -447,7 +451,8 @@ a {
 }
 
 .in-band:hover > .anchor {
-	display: initial;
+	display: inline-block;
+	position: absolute;
 }
 .anchor {
 	display: none;
@@ -653,11 +658,13 @@ h3 > .collapse-toggle, h4 > .collapse-toggle {
 
 .toggle-wrapper {
 	position: relative;
+	margin-top: 5px;
 }
 
 .toggle-wrapper.collapsed {
-	height: 1em;
+	height: 25px;
 	transition: height .2s;
+	margin-bottom: .6em;
 }
 
 .collapse-toggle > .inner {
@@ -699,14 +706,16 @@ span.since {
 	margin-top: 5px;
 }
 
-.variant + .toggle-wrapper > a {
-	margin-top: 5px;
-}
-
 .sub-variant, .sub-variant > h3 {
 	margin-top: 0 !important;
 }
 
+.toggle-label {
+	display: inline-block;
+	margin-left: 4px;
+	margin-top: 3px;
+}
+
 .enum > .toggle-wrapper + .docblock, .struct > .toggle-wrapper + .docblock {
 	margin-left: 30px;
 	margin-bottom: 20px;
diff --git a/src/librustdoc/lib.rs b/src/librustdoc/lib.rs
index 61a8165d26af1..d04b6d3417a5a 100644
--- a/src/librustdoc/lib.rs
+++ b/src/librustdoc/lib.rs
@@ -28,6 +28,7 @@
 extern crate arena;
 extern crate getopts;
 extern crate env_logger;
+extern crate html_diff;
 extern crate libc;
 extern crate rustc;
 extern crate rustc_data_structures;
diff --git a/src/librustdoc/test.rs b/src/librustdoc/test.rs
index 47e8d63f80aa0..5d74cbdf56a19 100644
--- a/src/librustdoc/test.rs
+++ b/src/librustdoc/test.rs
@@ -532,7 +532,7 @@ impl Collector {
 
     pub fn get_line(&self) -> usize {
         if let Some(ref codemap) = self.codemap {
-            let line = self.position.lo.to_usize();
+            let line = self.position.lo().to_usize();
             let line = codemap.lookup_char_pos(BytePos(line as u32)).line;
             if line > 0 { line - 1 } else { line }
         } else {
diff --git a/src/librustdoc/visit_ast.rs b/src/librustdoc/visit_ast.rs
index e3426fba1bca1..1f33cd7765164 100644
--- a/src/librustdoc/visit_ast.rs
+++ b/src/librustdoc/visit_ast.rs
@@ -199,8 +199,9 @@ impl<'a, 'tcx> RustdocVisitor<'a, 'tcx> {
             self.visit_item(item, None, &mut om);
         }
         self.inside_public_path = orig_inside_public_path;
-        if let Some(exports) = self.cx.tcx.export_map.get(&id) {
-            for export in exports {
+        let hir_id = self.cx.tcx.hir.node_to_hir_id(id);
+        if let Some(exports) = self.cx.tcx.module_exports(hir_id) {
+            for export in exports.iter() {
                 if let Def::Macro(def_id, ..) = export.def {
                     if def_id.krate == LOCAL_CRATE || self.reexported_macros.contains(&def_id) {
                         continue // These are `krate.exported_macros`, handled in `self.visit()`.
diff --git a/src/libstd/lib.rs b/src/libstd/lib.rs
index b57067e35e9d9..33bf0d68126d4 100644
--- a/src/libstd/lib.rs
+++ b/src/libstd/lib.rs
@@ -322,14 +322,12 @@
 // if the user has disabled jemalloc in `./configure`).
 // `force_alloc_system` is *only* intended as a workaround for local rebuilds
 // with a rustc without jemalloc.
-// The not(stage0+msvc) gates will only last until the next stage0 bump
-#![cfg_attr(all(
-        not(all(stage0, target_env = "msvc")),
-        any(stage0, feature = "force_alloc_system")),
-    feature(global_allocator))]
-#[cfg(all(
-    not(all(stage0, target_env = "msvc")),
-    any(stage0, feature = "force_alloc_system")))]
+// FIXME(#44236) shouldn't need MSVC logic
+#![cfg_attr(all(not(target_env = "msvc"),
+                any(stage0, feature = "force_alloc_system")),
+            feature(global_allocator))]
+#[cfg(all(not(target_env = "msvc"),
+          any(stage0, feature = "force_alloc_system")))]
 #[global_allocator]
 static ALLOC: alloc_system::System = alloc_system::System;
 
diff --git a/src/libstd/macros.rs b/src/libstd/macros.rs
index c426bf8086eef..72d561fae3bd9 100644
--- a/src/libstd/macros.rs
+++ b/src/libstd/macros.rs
@@ -14,25 +14,35 @@
 //! library. Each macro is available for use when linking against the standard
 //! library.
 
-#[macro_export]
-// This stability attribute is totally useless.
-#[stable(feature = "rust1", since = "1.0.0")]
-#[cfg(stage0)]
-macro_rules! __rust_unstable_column {
-    () => {
-        column!()
-    }
-}
-
 /// The entry point for panic of Rust threads.
 ///
+/// This allows a program to to terminate immediately and provide feedback
+/// to the caller of the program. `panic!` should be used when a program reaches
+/// an unrecoverable problem.
+///
+/// This macro is the perfect way to assert conditions in example code and in
+/// tests.  `panic!` is closely tied with the `unwrap` method of both [`Option`]
+/// and [`Result`][runwrap] enums.  Both implementations call `panic!` when they are set
+/// to None or Err variants.
+///
 /// This macro is used to inject panic into a Rust thread, causing the thread to
 /// panic entirely. Each thread's panic can be reaped as the `Box<Any>` type,
 /// and the single-argument form of the `panic!` macro will be the value which
 /// is transmitted.
 ///
+/// [`Result`] enum is often a better solution for recovering from errors than
+/// using the `panic!` macro.  This macro should be used to avoid proceeding using
+/// incorrect values, such as from external sources.  Detailed information about
+/// error handling is found in the [book].
+///
 /// The multi-argument form of this macro panics with a string and has the
-/// `format!` syntax for building a string.
+/// [`format!`] syntax for building a string.
+///
+/// [runwrap]: ../std/result/enum.Result.html#method.unwrap
+/// [`Option`]: ../std/option/enum.Option.html#method.unwrap
+/// [`Result`]: ../std/result/enum.Result.html
+/// [`format!`]: ../std/macro.format.html
+/// [book]: ../book/second-edition/ch09-01-unrecoverable-errors-with-panic.html
 ///
 /// # Current implementation
 ///
@@ -78,15 +88,19 @@ macro_rules! panic {
 
 /// Macro for printing to the standard output.
 ///
-/// Equivalent to the `println!` macro except that a newline is not printed at
+/// Equivalent to the [`println!`] macro except that a newline is not printed at
 /// the end of the message.
 ///
 /// Note that stdout is frequently line-buffered by default so it may be
-/// necessary to use `io::stdout().flush()` to ensure the output is emitted
+/// necessary to use [`io::stdout().flush()`][flush] to ensure the output is emitted
 /// immediately.
 ///
 /// Use `print!` only for the primary output of your program.  Use
-/// `eprint!` instead to print error and progress messages.
+/// [`eprint!`] instead to print error and progress messages.
+///
+/// [`println!`]: ../std/macro.println.html
+/// [flush]: ../std/io/trait.Write.html#tymethod.flush
+/// [`eprint!`]: ../std/macro.eprint.html
 ///
 /// # Panics
 ///
@@ -118,16 +132,20 @@ macro_rules! print {
     ($($arg:tt)*) => ($crate::io::_print(format_args!($($arg)*)));
 }
 
-/// Macro for printing to the standard output, with a newline. On all
-/// platforms, the newline is the LINE FEED character (`\n`/`U+000A`) alone
+/// Macro for printing to the standard output, with a newline.
+///
+/// On all platforms, the newline is the LINE FEED character (`\n`/`U+000A`) alone
 /// (no additional CARRIAGE RETURN (`\r`/`U+000D`).
 ///
-/// Use the `format!` syntax to write data to the standard output.
-/// See `std::fmt` for more information.
+/// Use the [`format!`] syntax to write data to the standard output.
+/// See [`std::fmt`] for more information.
 ///
 /// Use `println!` only for the primary output of your program.  Use
-/// `eprintln!` instead to print error and progress messages.
+/// [`eprintln!`] instead to print error and progress messages.
 ///
+/// [`format!`]: ../std/macro.format.html
+/// [`std::fmt`]: ../std/fmt/index.html
+/// [`eprintln!`]: ../std/macro.eprint.html
 /// # Panics
 ///
 /// Panics if writing to `io::stdout` fails.
@@ -149,16 +167,25 @@ macro_rules! println {
 
 /// Macro for printing to the standard error.
 ///
-/// Equivalent to the `print!` macro, except that output goes to
-/// `io::stderr` instead of `io::stdout`.  See `print!` for
+/// Equivalent to the [`print!`] macro, except that output goes to
+/// [`io::stderr`] instead of `io::stdout`.  See [`print!`] for
 /// example usage.
 ///
 /// Use `eprint!` only for error and progress messages.  Use `print!`
 /// instead for the primary output of your program.
 ///
+/// [`io::stderr`]: ../std/io/struct.Stderr.html
+/// [`print!`]: ../std/macro.print.html
+///
 /// # Panics
 ///
 /// Panics if writing to `io::stderr` fails.
+///
+/// # Examples
+///
+/// ```
+/// eprint!("Error: Could not complete task");
+/// ```
 #[macro_export]
 #[stable(feature = "eprint", since = "1.19.0")]
 #[allow_internal_unstable]
@@ -168,16 +195,25 @@ macro_rules! eprint {
 
 /// Macro for printing to the standard error, with a newline.
 ///
-/// Equivalent to the `println!` macro, except that output goes to
-/// `io::stderr` instead of `io::stdout`.  See `println!` for
+/// Equivalent to the [`println!`] macro, except that output goes to
+/// [`io::stderr`] instead of `io::stdout`.  See [`println!`] for
 /// example usage.
 ///
 /// Use `eprintln!` only for error and progress messages.  Use `println!`
 /// instead for the primary output of your program.
 ///
+/// [`io::stderr`]: ../std/io/struct.Stderr.html
+/// [`println!`]: ../std/macro.println.html
+///
 /// # Panics
 ///
 /// Panics if writing to `io::stderr` fails.
+///
+/// # Examples
+///
+/// ```
+/// eprintln!("Error: Could not complete task");
+/// ```
 #[macro_export]
 #[stable(feature = "eprint", since = "1.19.0")]
 macro_rules! eprintln {
@@ -267,13 +303,23 @@ pub mod builtin {
 
     /// The core macro for formatted string creation & output.
     ///
+    /// This macro functions by taking a formatting string literal containing
+    /// `{}` for each additional argument passed.  `format_args!` prepares the
+    /// additional parameters to ensure the output can be interpreted as a string
+    /// and canonicalizes the arguments into a single type.  Any value that implements
+    /// the [`Display`] trait can be passed to `format_args!`, as can any
+    /// [`Debug`] implementation be passed to a `{:?}` within the formatting string.
+    ///
     /// This macro produces a value of type [`fmt::Arguments`]. This value can be
-    /// passed to the functions in [`std::fmt`] for performing useful functions.
+    /// passed to the macros within [`std::fmt`] for performing useful redirection.
     /// All other formatting macros ([`format!`], [`write!`], [`println!`], etc) are
-    /// proxied through this one.
+    /// proxied through this one.  `format_args!`, unlike its derived macros, avoids
+    /// heap allocations.
     ///
     /// For more information, see the documentation in [`std::fmt`].
     ///
+    /// [`Display`]: ../std/fmt/trait.Display.html
+    /// [`Debug`]: ../std/fmt/trait.Debug.html
     /// [`fmt::Arguments`]: ../std/fmt/struct.Arguments.html
     /// [`std::fmt`]: ../std/fmt/index.html
     /// [`format!`]: ../std/macro.format.html
@@ -301,9 +347,11 @@ pub mod builtin {
     /// compile time, yielding an expression of type `&'static str`.
     ///
     /// If the environment variable is not defined, then a compilation error
-    /// will be emitted.  To not emit a compile error, use the `option_env!`
+    /// will be emitted.  To not emit a compile error, use the [`option_env!`]
     /// macro instead.
     ///
+    /// [`option_env!`]: ../std/macro.option_env.html
+    ///
     /// # Examples
     ///
     /// ```
@@ -319,11 +367,14 @@ pub mod builtin {
     /// If the named environment variable is present at compile time, this will
     /// expand into an expression of type `Option<&'static str>` whose value is
     /// `Some` of the value of the environment variable. If the environment
-    /// variable is not present, then this will expand to `None`.
+    /// variable is not present, then this will expand to `None`.  See
+    /// [`Option<T>`][option] for more information on this type.
     ///
     /// A compile time error is never emitted when using this macro regardless
     /// of whether the environment variable is present or not.
     ///
+    /// [option]: ../std/option/enum.Option.html
+    ///
     /// # Examples
     ///
     /// ```
@@ -385,10 +436,16 @@ pub mod builtin {
 
     /// A macro which expands to the line number on which it was invoked.
     ///
+    /// With [`column!`] and [`file!`], these macros provide debugging information for
+    /// developers about the location within the source.
+    ///
     /// The expanded expression has type `u32`, and the returned line is not
     /// the invocation of the `line!()` macro itself, but rather the first macro
     /// invocation leading up to the invocation of the `line!()` macro.
     ///
+    /// [`column!`]: macro.column.html
+    /// [`file!`]: macro.file.html
+    ///
     /// # Examples
     ///
     /// ```
@@ -401,9 +458,15 @@ pub mod builtin {
 
     /// A macro which expands to the column number on which it was invoked.
     ///
+    /// With [`line!`] and [`file!`], these macros provide debugging information for
+    /// developers about the location within the source.
+    ///
     /// The expanded expression has type `u32`, and the returned column is not
-    /// the invocation of the `column!()` macro itself, but rather the first macro
-    /// invocation leading up to the invocation of the `column!()` macro.
+    /// the invocation of the `column!` macro itself, but rather the first macro
+    /// invocation leading up to the invocation of the `column!` macro.
+    ///
+    /// [`line!`]: macro.line.html
+    /// [`file!`]: macro.file.html
     ///
     /// # Examples
     ///
@@ -417,11 +480,18 @@ pub mod builtin {
 
     /// A macro which expands to the file name from which it was invoked.
     ///
+    /// With [`line!`] and [`column!`], these macros provide debugging information for
+    /// developers about the location within the source.
+    ///
+    ///
     /// The expanded expression has type `&'static str`, and the returned file
-    /// is not the invocation of the `file!()` macro itself, but rather the
-    /// first macro invocation leading up to the invocation of the `file!()`
+    /// is not the invocation of the `file!` macro itself, but rather the
+    /// first macro invocation leading up to the invocation of the `file!`
     /// macro.
     ///
+    /// [`line!`]: macro.line.html
+    /// [`column!`]: macro.column.html
+    ///
     /// # Examples
     ///
     /// ```
diff --git a/src/libstd/net/addr.rs b/src/libstd/net/addr.rs
index 36c06dc0b58d0..e1d7a2531b6c9 100644
--- a/src/libstd/net/addr.rs
+++ b/src/libstd/net/addr.rs
@@ -705,30 +705,74 @@ impl hash::Hash for SocketAddrV6 {
 ///
 /// # Examples
 ///
+/// Creating a [`SocketAddr`] iterator that yields one item:
+///
+/// ```
+/// use std::net::{ToSocketAddrs, SocketAddr};
+///
+/// let addr = SocketAddr::from(([127, 0, 0, 1], 443));
+/// let mut addrs_iter = addr.to_socket_addrs().unwrap();
+///
+/// assert_eq!(Some(addr), addrs_iter.next());
+/// assert!(addrs_iter.next().is_none());
+/// ```
+///
+/// Creating a [`SocketAddr`] iterator from a hostname:
+///
 /// ```no_run
-/// use std::net::{SocketAddrV4, TcpStream, UdpSocket, TcpListener, Ipv4Addr};
-///
-/// fn main() {
-///     let ip = Ipv4Addr::new(127, 0, 0, 1);
-///     let port = 12345;
-///
-///     // The following lines are equivalent modulo possible "localhost" name
-///     // resolution differences
-///     let tcp_s = TcpStream::connect(SocketAddrV4::new(ip, port));
-///     let tcp_s = TcpStream::connect((ip, port));
-///     let tcp_s = TcpStream::connect(("127.0.0.1", port));
-///     let tcp_s = TcpStream::connect(("localhost", port));
-///     let tcp_s = TcpStream::connect("127.0.0.1:12345");
-///     let tcp_s = TcpStream::connect("localhost:12345");
-///
-///     // TcpListener::bind(), UdpSocket::bind() and UdpSocket::send_to()
-///     // behave similarly
-///     let tcp_l = TcpListener::bind("localhost:12345");
-///
-///     let mut udp_s = UdpSocket::bind(("127.0.0.1", port)).unwrap();
-///     udp_s.send_to(&[7], (ip, 23451)).unwrap();
-/// }
+/// use std::net::{SocketAddr, ToSocketAddrs};
+///
+/// // assuming 'localhost' resolves to 127.0.0.1
+/// let mut addrs_iter = "localhost:443".to_socket_addrs().unwrap();
+/// assert_eq!(addrs_iter.next(), Some(SocketAddr::from(([127, 0, 0, 1], 443))));
+/// assert!(addrs_iter.next().is_none());
+///
+/// // assuming 'foo' does not resolve
+/// assert!("foo:443".to_socket_addrs().is_err());
 /// ```
+///
+/// Creating a [`SocketAddr`] iterator that yields multiple items:
+///
+/// ```
+/// use std::net::{SocketAddr, ToSocketAddrs};
+///
+/// let addr1 = SocketAddr::from(([0, 0, 0, 0], 80));
+/// let addr2 = SocketAddr::from(([127, 0, 0, 1], 443));
+/// let addrs = vec![addr1, addr2];
+///
+/// let mut addrs_iter = (&addrs[..]).to_socket_addrs().unwrap();
+///
+/// assert_eq!(Some(addr1), addrs_iter.next());
+/// assert_eq!(Some(addr2), addrs_iter.next());
+/// assert!(addrs_iter.next().is_none());
+/// ```
+///
+/// Attempting to create a [`SocketAddr`] iterator from an improperly formatted
+/// socket address `&str` (missing the port):
+///
+/// ```
+/// use std::io;
+/// use std::net::ToSocketAddrs;
+///
+/// let err = "127.0.0.1".to_socket_addrs().unwrap_err();
+/// assert_eq!(err.kind(), io::ErrorKind::InvalidInput);
+/// ```
+///
+/// [`TcpStream::connect`] is an example of an function that utilizes
+/// `ToSocketsAddr` as a trait bound on its parameter in order to accept
+/// different types:
+///
+/// ```no_run
+/// use std::net::{TcpStream, Ipv4Addr};
+///
+/// let stream = TcpStream::connect(("127.0.0.1", 443));
+/// // or
+/// let stream = TcpStream::connect("127.0.0.1:443");
+/// // or
+/// let stream = TcpStream::connect((Ipv4Addr::new(127, 0, 0, 1), 443));
+/// ```
+///
+/// [`TcpStream::connect`]: ../../std/net/struct.TcpStream.html#method.connect
 #[stable(feature = "rust1", since = "1.0.0")]
 pub trait ToSocketAddrs {
     /// Returned iterator over socket addresses which this type may correspond
diff --git a/src/libstd/net/tcp.rs b/src/libstd/net/tcp.rs
index 2eabb46441b32..5467eff202b02 100644
--- a/src/libstd/net/tcp.rs
+++ b/src/libstd/net/tcp.rs
@@ -111,15 +111,18 @@ impl TcpStream {
     /// `addr` is an address of the remote host. Anything which implements
     /// [`ToSocketAddrs`] trait can be supplied for the address; see this trait
     /// documentation for concrete examples.
-    /// In case [`ToSocketAddrs::to_socket_addrs()`] returns more than one entry,
-    /// then the first valid and reachable address is used.
+    ///
+    /// If `addr` yields multiple addresses, `connect` will be attempted with
+    /// each of the addresses until a connection is successful. If none of
+    /// the addresses result in a successful connection, the error returned from
+    /// the last connection attempt (the last address) is returned.
     ///
     /// [`ToSocketAddrs`]: ../../std/net/trait.ToSocketAddrs.html
-    /// [`ToSocketAddrs::to_socket_addrs()`]:
-    /// ../../std/net/trait.ToSocketAddrs.html#tymethod.to_socket_addrs
     ///
     /// # Examples
     ///
+    /// Open a TCP connection to `127.0.0.1:8080`:
+    ///
     /// ```no_run
     /// use std::net::TcpStream;
     ///
@@ -129,6 +132,23 @@ impl TcpStream {
     ///     println!("Couldn't connect to server...");
     /// }
     /// ```
+    ///
+    /// Open a TCP connection to `127.0.0.1:8080`. If the connection fails, open
+    /// a TCP connection to `127.0.0.1:8081`:
+    ///
+    /// ```no_run
+    /// use std::net::{SocketAddr, TcpStream};
+    ///
+    /// let addrs = [
+    ///     SocketAddr::from(([127, 0, 0, 1], 8080)),
+    ///     SocketAddr::from(([127, 0, 0, 1], 8081)),
+    /// ];
+    /// if let Ok(stream) = TcpStream::connect(&addrs[..]) {
+    ///     println!("Connected to the server!");
+    /// } else {
+    ///     println!("Couldn't connect to server...");
+    /// }
+    /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn connect<A: ToSocketAddrs>(addr: A) -> io::Result<TcpStream> {
         super::each_addr(addr, net_imp::TcpStream::connect).map(TcpStream)
@@ -557,16 +577,36 @@ impl TcpListener {
     /// The address type can be any implementor of [`ToSocketAddrs`] trait. See
     /// its documentation for concrete examples.
     ///
+    /// If `addr` yields multiple addresses, `bind` will be attempted with
+    /// each of the addresses until one succeeds and returns the listener. If
+    /// none of the addresses succeed in creating a listener, the error returned
+    /// from the last attempt (the last address) is returned.
+    ///
     /// [`local_addr`]: #method.local_addr
     /// [`ToSocketAddrs`]: ../../std/net/trait.ToSocketAddrs.html
     ///
     /// # Examples
     ///
+    /// Create a TCP listener bound to `127.0.0.1:80`:
+    ///
     /// ```no_run
     /// use std::net::TcpListener;
     ///
     /// let listener = TcpListener::bind("127.0.0.1:80").unwrap();
     /// ```
+    ///
+    /// Create a TCP listener bound to `127.0.0.1:80`. If that fails, create a
+    /// TCP listener bound to `127.0.0.1:443`:
+    ///
+    /// ```no_run
+    /// use std::net::{SocketAddr, TcpListener};
+    ///
+    /// let addrs = [
+    ///     SocketAddr::from(([127, 0, 0, 1], 80)),
+    ///     SocketAddr::from(([127, 0, 0, 1], 443)),
+    /// ];
+    /// let listener = TcpListener::bind(&addrs[..]).unwrap();
+    /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn bind<A: ToSocketAddrs>(addr: A) -> io::Result<TcpListener> {
         super::each_addr(addr, net_imp::TcpListener::bind).map(TcpListener)
diff --git a/src/libstd/net/udp.rs b/src/libstd/net/udp.rs
index 9aff989788536..35001833383c0 100644
--- a/src/libstd/net/udp.rs
+++ b/src/libstd/net/udp.rs
@@ -69,14 +69,34 @@ impl UdpSocket {
     /// The address type can be any implementor of [`ToSocketAddrs`] trait. See
     /// its documentation for concrete examples.
     ///
+    /// If `addr` yields multiple addresses, `bind` will be attempted with
+    /// each of the addresses until one succeeds and returns the socket. If none
+    /// of the addresses succeed in creating a socket, the error returned from
+    /// the last attempt (the last address) is returned.
+    ///
     /// [`ToSocketAddrs`]: ../../std/net/trait.ToSocketAddrs.html
     ///
     /// # Examples
     ///
+    /// Create a UDP socket bound to `127.0.0.1:3400`:
+    ///
     /// ```no_run
     /// use std::net::UdpSocket;
     ///
-    /// let socket = UdpSocket::bind("127.0.0.1:34254").expect("couldn't bind to address");
+    /// let socket = UdpSocket::bind("127.0.0.1:3400").expect("couldn't bind to address");
+    /// ```
+    ///
+    /// Create a UDP socket bound to `127.0.0.1:3400`. If the socket cannot be
+    /// bound to that address, create a UDP socket bound to `127.0.0.1:3401`:
+    ///
+    /// ```no_run
+    /// use std::net::{SocketAddr, UdpSocket};
+    ///
+    /// let addrs = [
+    ///     SocketAddr::from(([127, 0, 0, 1], 3400)),
+    ///     SocketAddr::from(([127, 0, 0, 1], 3401)),
+    /// ];
+    /// let socket = UdpSocket::bind(&addrs[..]).expect("couldn't bind to address");
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn bind<A: ToSocketAddrs>(addr: A) -> io::Result<UdpSocket> {
@@ -130,6 +150,9 @@ impl UdpSocket {
     /// Address type can be any implementor of [`ToSocketAddrs`] trait. See its
     /// documentation for concrete examples.
     ///
+    /// It is possible for `addr` to yield multiple addresses, but `send_to`
+    /// will only send data to the first address yielded by `addr`.
+    ///
     /// This will return an error when the IP version of the local socket
     /// does not match that returned from [`ToSocketAddrs`].
     ///
@@ -562,14 +585,37 @@ impl UdpSocket {
     /// `recv` syscalls to be used to send data and also applies filters to only
     /// receive data from the specified address.
     ///
+    /// If `addr` yields multiple addresses, `connect` will be attempted with
+    /// each of the addresses until a connection is successful. If none of
+    /// the addresses are able to be connected, the error returned from the
+    /// last connection attempt (the last address) is returned.
+    ///
     /// # Examples
     ///
+    /// Create a UDP socket bound to `127.0.0.1:3400` and connect the socket to
+    /// `127.0.0.1:8080`:
+    ///
     /// ```no_run
     /// use std::net::UdpSocket;
     ///
-    /// let socket = UdpSocket::bind("127.0.0.1:34254").expect("couldn't bind to address");
+    /// let socket = UdpSocket::bind("127.0.0.1:3400").expect("couldn't bind to address");
     /// socket.connect("127.0.0.1:8080").expect("connect function failed");
     /// ```
+    ///
+    /// Create a UDP socket bound to `127.0.0.1:3400` and connect the socket to
+    /// `127.0.0.1:8080`. If that connection fails, then the UDP socket will
+    /// connect to `127.0.0.1:8081`:
+    ///
+    /// ```no_run
+    /// use std::net::{SocketAddr, UdpSocket};
+    ///
+    /// let socket = UdpSocket::bind("127.0.0.1:3400").expect("couldn't bind to address");
+    /// let connect_addrs = [
+    ///     SocketAddr::from(([127, 0, 0, 1], 8080)),
+    ///     SocketAddr::from(([127, 0, 0, 1], 8081)),
+    /// ];
+    /// socket.connect(&connect_addrs[..]).expect("connect function failed");
+    /// ```
     #[stable(feature = "net2_mutators", since = "1.9.0")]
     pub fn connect<A: ToSocketAddrs>(&self, addr: A) -> io::Result<()> {
         super::each_addr(addr, |addr| self.0.connect(addr))
diff --git a/src/libstd/os/raw.rs b/src/libstd/os/raw.rs
index c34491941d690..fe0427d4e5f9c 100644
--- a/src/libstd/os/raw.rs
+++ b/src/libstd/os/raw.rs
@@ -14,8 +14,7 @@
 
 use fmt;
 
-#[cfg(any(target_os = "emscripten",
-          all(target_os = "linux", any(target_arch = "aarch64",
+#[cfg(any(all(target_os = "linux", any(target_arch = "aarch64",
                                        target_arch = "arm",
                                        target_arch = "powerpc",
                                        target_arch = "powerpc64",
@@ -24,8 +23,7 @@ use fmt;
                                          target_arch = "arm")),
           all(target_os = "fuchsia", target_arch = "aarch64")))]
 #[stable(feature = "raw_os", since = "1.1.0")] pub type c_char = u8;
-#[cfg(not(any(target_os = "emscripten",
-              all(target_os = "linux", any(target_arch = "aarch64",
+#[cfg(not(any(all(target_os = "linux", any(target_arch = "aarch64",
                                            target_arch = "arm",
                                            target_arch = "powerpc",
                                            target_arch = "powerpc64",
diff --git a/src/libstd/panicking.rs b/src/libstd/panicking.rs
index 739dc4163feb3..80ce15944a5c3 100644
--- a/src/libstd/panicking.rs
+++ b/src/libstd/panicking.rs
@@ -522,40 +522,6 @@ pub fn begin_panic_fmt(msg: &fmt::Arguments,
     begin_panic(s, file_line_col)
 }
 
-// FIXME: In PR #42938, we have added the column as info passed to the panic
-// handling code. For this, we want to break the ABI of begin_panic.
-// This is not possible to do directly, as the stage0 compiler is hardcoded
-// to emit a call to begin_panic in src/libsyntax/ext/build.rs, only
-// with the file and line number being passed, but not the colum number.
-// By changing the compiler source, we can only affect behaviour of higher
-// stages. We need to perform the switch over two stage0 replacements, using
-// a temporary function begin_panic_new while performing the switch:
-// 0. Before the current switch, we told stage1 onward to emit a call
-//    to begin_panic_new.
-// 1. Right now, stage0 calls begin_panic_new with the new ABI,
-//    begin_panic stops being used. We have changed begin_panic to
-//    the new ABI, and started to emit calls to begin_panic in higher
-//    stages again, this time with the new ABI.
-// 2. After the second SNAP, stage0 calls begin_panic with the new ABI,
-//    and we can remove the temporary begin_panic_new function.
-
-/// This is the entry point of panicking for panic!() and assert!().
-#[cfg(stage0)]
-#[unstable(feature = "libstd_sys_internals",
-           reason = "used by the panic! macro",
-           issue = "0")]
-#[inline(never)] #[cold] // avoid code bloat at the call sites as much as possible
-pub fn begin_panic_new<M: Any + Send>(msg: M, file_line_col: &(&'static str, u32, u32)) -> ! {
-    // Note that this should be the only allocation performed in this code path.
-    // Currently this means that panic!() on OOM will invoke this code path,
-    // but then again we're not really ready for panic on OOM anyway. If
-    // we do start doing this, then we should propagate this allocation to
-    // be performed in the parent of this thread instead of the thread that's
-    // panicking.
-
-    rust_panic_with_hook(Box::new(msg), file_line_col)
-}
-
 /// This is the entry point of panicking for panic!() and assert!().
 #[unstable(feature = "libstd_sys_internals",
            reason = "used by the panic! macro",
diff --git a/src/libstd/rt.rs b/src/libstd/rt.rs
index 2aa23ea043b5b..06fd838ea06d9 100644
--- a/src/libstd/rt.rs
+++ b/src/libstd/rt.rs
@@ -25,8 +25,6 @@
 
 
 // Reexport some of our utilities which are expected by other crates.
-#[cfg(stage0)]
-pub use panicking::begin_panic_new;
 pub use panicking::{begin_panic, begin_panic_fmt, update_panic_count};
 
 #[cfg(not(test))]
diff --git a/src/libstd/sys/unix/fd.rs b/src/libstd/sys/unix/fd.rs
index 138087f165142..f50b093acc848 100644
--- a/src/libstd/sys/unix/fd.rs
+++ b/src/libstd/sys/unix/fd.rs
@@ -71,13 +71,21 @@ impl FileDesc {
         #[cfg(target_os = "android")]
         use super::android::cvt_pread64;
 
-        #[cfg(not(target_os = "android"))]
+        #[cfg(target_os = "emscripten")]
         unsafe fn cvt_pread64(fd: c_int, buf: *mut c_void, count: usize, offset: i64)
             -> io::Result<isize>
         {
-            #[cfg(any(target_os = "linux", target_os = "emscripten"))]
             use libc::pread64;
-            #[cfg(not(any(target_os = "linux", target_os = "emscripten")))]
+            cvt(pread64(fd, buf, count, offset as i32))
+        }
+
+        #[cfg(not(any(target_os = "android", target_os = "emscripten")))]
+        unsafe fn cvt_pread64(fd: c_int, buf: *mut c_void, count: usize, offset: i64)
+            -> io::Result<isize>
+        {
+            #[cfg(target_os = "linux")]
+            use libc::pread64;
+            #[cfg(not(target_os = "linux"))]
             use libc::pread as pread64;
             cvt(pread64(fd, buf, count, offset))
         }
@@ -104,13 +112,21 @@ impl FileDesc {
         #[cfg(target_os = "android")]
         use super::android::cvt_pwrite64;
 
-        #[cfg(not(target_os = "android"))]
+        #[cfg(target_os = "emscripten")]
+        unsafe fn cvt_pwrite64(fd: c_int, buf: *const c_void, count: usize, offset: i64)
+            -> io::Result<isize>
+        {
+            use libc::pwrite64;
+            cvt(pwrite64(fd, buf, count, offset as i32))
+        }
+
+        #[cfg(not(any(target_os = "android", target_os = "emscripten")))]
         unsafe fn cvt_pwrite64(fd: c_int, buf: *const c_void, count: usize, offset: i64)
             -> io::Result<isize>
         {
-            #[cfg(any(target_os = "linux", target_os = "emscripten"))]
+            #[cfg(target_os = "linux")]
             use libc::pwrite64;
-            #[cfg(not(any(target_os = "linux", target_os = "emscripten")))]
+            #[cfg(not(target_os = "linux"))]
             use libc::pwrite as pwrite64;
             cvt(pwrite64(fd, buf, count, offset))
         }
diff --git a/src/libstd/sys/unix/fs.rs b/src/libstd/sys/unix/fs.rs
index cb0f687e0721c..f94af4913324f 100644
--- a/src/libstd/sys/unix/fs.rs
+++ b/src/libstd/sys/unix/fs.rs
@@ -514,6 +514,8 @@ impl File {
             SeekFrom::End(off) => (libc::SEEK_END, off),
             SeekFrom::Current(off) => (libc::SEEK_CUR, off),
         };
+        #[cfg(target_os = "emscripten")]
+        let pos = pos as i32;
         let n = cvt(unsafe { lseek64(self.0.raw(), pos, whence) })?;
         Ok(n as u64)
     }
diff --git a/src/libstd/sys/unix/process/process_unix.rs b/src/libstd/sys/unix/process/process_unix.rs
index edd322ca6fa07..ae24021fb6c3a 100644
--- a/src/libstd/sys/unix/process/process_unix.rs
+++ b/src/libstd/sys/unix/process/process_unix.rs
@@ -10,7 +10,6 @@
 
 use io::{self, Error, ErrorKind};
 use libc::{self, c_int, gid_t, pid_t, uid_t};
-use mem;
 use ptr;
 
 use sys::cvt;
@@ -184,7 +183,9 @@ impl Command {
         }
 
         // NaCl has no signal support.
-        if cfg!(not(any(target_os = "nacl", target_os = "emscripten"))) {
+        #[cfg(not(any(target_os = "nacl", target_os = "emscripten")))]
+        {
+            use mem;
             // Reset signal handling so the child process starts in a
             // standardized state. libstd ignores SIGPIPE, and signal-handling
             // libraries often set a mask. Child processes inherit ignored
diff --git a/src/libstd/thread/local.rs b/src/libstd/thread/local.rs
index 7a9b642350fa6..02347bf4906a6 100644
--- a/src/libstd/thread/local.rs
+++ b/src/libstd/thread/local.rs
@@ -157,7 +157,7 @@ macro_rules! thread_local {
            issue = "0")]
 #[macro_export]
 #[allow_internal_unstable]
-#[cfg_attr(not(stage0), allow_internal_unsafe)]
+#[allow_internal_unsafe]
 macro_rules! __thread_local_inner {
     ($(#[$attr:meta])* $vis:vis $name:ident, $t:ty, $init:expr) => {
         $(#[$attr])* $vis static $name: $crate::thread::LocalKey<$t> = {
@@ -394,9 +394,6 @@ pub mod fast {
         }
     }
 
-    #[cfg(stage0)]
-    unsafe impl<T> ::marker::Sync for Key<T> { }
-
     impl<T> Key<T> {
         pub const fn new() -> Key<T> {
             Key {
diff --git a/src/libsyntax/ast.rs b/src/libsyntax/ast.rs
index fa4df2196a3c5..720f6cd32bdf8 100644
--- a/src/libsyntax/ast.rs
+++ b/src/libsyntax/ast.rs
@@ -134,7 +134,7 @@ impl PathSegment {
     }
     pub fn crate_root(span: Span) -> Self {
         PathSegment {
-            identifier: Ident { ctxt: span.ctxt, ..keywords::CrateRoot.ident() },
+            identifier: Ident { ctxt: span.ctxt(), ..keywords::CrateRoot.ident() },
             span,
             parameters: None,
         }
@@ -810,6 +810,7 @@ pub struct Arm {
     pub pats: Vec<P<Pat>>,
     pub guard: Option<P<Expr>>,
     pub body: P<Expr>,
+    pub beginning_vert: Option<Span>, // For RFC 1925 feature gate
 }
 
 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
@@ -1016,6 +1017,9 @@ pub enum ExprKind {
 
     /// `expr?`
     Try(P<Expr>),
+
+    /// A `yield`, with an optional value to be yielded
+    Yield(Option<P<Expr>>),
 }
 
 /// The explicit Self type in a "qualified path". The actual
diff --git a/src/libsyntax/attr.rs b/src/libsyntax/attr.rs
index ca87c807103fd..adbbc1b0ac588 100644
--- a/src/libsyntax/attr.rs
+++ b/src/libsyntax/attr.rs
@@ -490,6 +490,10 @@ pub fn contains_name(attrs: &[Attribute], name: &str) -> bool {
     })
 }
 
+pub fn find_by_name<'a>(attrs: &'a [Attribute], name: &str) -> Option<&'a Attribute> {
+    attrs.iter().find(|attr| attr.check_name(name))
+}
+
 pub fn first_attr_value_str_by_name(attrs: &[Attribute], name: &str) -> Option<Symbol> {
     attrs.iter()
         .find(|at| at.check_name(name))
@@ -581,6 +585,20 @@ pub fn requests_inline(attrs: &[Attribute]) -> bool {
 
 /// Tests if a cfg-pattern matches the cfg set
 pub fn cfg_matches(cfg: &ast::MetaItem, sess: &ParseSess, features: Option<&Features>) -> bool {
+    eval_condition(cfg, sess, &mut |cfg| {
+        if let (Some(feats), Some(gated_cfg)) = (features, GatedCfg::gate(cfg)) {
+            gated_cfg.check_and_emit(sess, feats);
+        }
+        sess.config.contains(&(cfg.name(), cfg.value_str()))
+    })
+}
+
+/// Evaluate a cfg-like condition (with `any` and `all`), using `eval` to
+/// evaluate individual items.
+pub fn eval_condition<F>(cfg: &ast::MetaItem, sess: &ParseSess, eval: &mut F)
+                         -> bool
+    where F: FnMut(&ast::MetaItem) -> bool
+{
     match cfg.node {
         ast::MetaItemKind::List(ref mis) => {
             for mi in mis.iter() {
@@ -594,10 +612,10 @@ pub fn cfg_matches(cfg: &ast::MetaItem, sess: &ParseSess, features: Option<&Feat
             // that they won't fail with the loop above.
             match &*cfg.name.as_str() {
                 "any" => mis.iter().any(|mi| {
-                    cfg_matches(mi.meta_item().unwrap(), sess, features)
+                    eval_condition(mi.meta_item().unwrap(), sess, eval)
                 }),
                 "all" => mis.iter().all(|mi| {
-                    cfg_matches(mi.meta_item().unwrap(), sess, features)
+                    eval_condition(mi.meta_item().unwrap(), sess, eval)
                 }),
                 "not" => {
                     if mis.len() != 1 {
@@ -605,7 +623,7 @@ pub fn cfg_matches(cfg: &ast::MetaItem, sess: &ParseSess, features: Option<&Feat
                         return false;
                     }
 
-                    !cfg_matches(mis[0].meta_item().unwrap(), sess, features)
+                    !eval_condition(mis[0].meta_item().unwrap(), sess, eval)
                 },
                 p => {
                     span_err!(sess.span_diagnostic, cfg.span, E0537, "invalid predicate `{}`", p);
@@ -614,10 +632,7 @@ pub fn cfg_matches(cfg: &ast::MetaItem, sess: &ParseSess, features: Option<&Feat
             }
         },
         ast::MetaItemKind::Word | ast::MetaItemKind::NameValue(..) => {
-            if let (Some(feats), Some(gated_cfg)) = (features, GatedCfg::gate(cfg)) {
-                gated_cfg.check_and_emit(sess, feats);
-            }
-            sess.config.contains(&(cfg.name(), cfg.value_str()))
+            eval(cfg)
         }
     }
 }
@@ -1055,7 +1070,7 @@ impl MetaItem {
     fn from_tokens<I>(tokens: &mut iter::Peekable<I>) -> Option<MetaItem>
         where I: Iterator<Item = TokenTree>,
     {
-        let (mut span, name) = match tokens.next() {
+        let (span, name) = match tokens.next() {
             Some(TokenTree::Token(span, Token::Ident(ident))) => (span, ident.name),
             Some(TokenTree::Token(_, Token::Interpolated(ref nt))) => match nt.0 {
                 token::Nonterminal::NtIdent(ident) => (ident.span, ident.node.name),
@@ -1064,17 +1079,17 @@ impl MetaItem {
             },
             _ => return None,
         };
-        let list_closing_paren_pos = tokens.peek().map(|tt| tt.span().hi);
+        let list_closing_paren_pos = tokens.peek().map(|tt| tt.span().hi());
         let node = match MetaItemKind::from_tokens(tokens) {
             Some(node) => node,
             _ => return None,
         };
-        span.hi = match node {
-            MetaItemKind::NameValue(ref lit) => lit.span.hi,
-            MetaItemKind::List(..) => list_closing_paren_pos.unwrap_or(span.hi),
-            _ => span.hi,
+        let hi = match node {
+            MetaItemKind::NameValue(ref lit) => lit.span.hi(),
+            MetaItemKind::List(..) => list_closing_paren_pos.unwrap_or(span.hi()),
+            _ => span.hi(),
         };
-        Some(MetaItem { name: name, span: span, node: node })
+        Some(MetaItem { name, node, span: span.with_hi(hi) })
     }
 }
 
diff --git a/src/libsyntax/codemap.rs b/src/libsyntax/codemap.rs
index 30ae7df93532e..cd4a6f921fe6f 100644
--- a/src/libsyntax/codemap.rs
+++ b/src/libsyntax/codemap.rs
@@ -34,8 +34,8 @@ use errors::CodeMapper;
 /// otherwise return the call site span up to the `enclosing_sp` by
 /// following the `expn_info` chain.
 pub fn original_sp(sp: Span, enclosing_sp: Span) -> Span {
-    let call_site1 = sp.ctxt.outer().expn_info().map(|ei| ei.call_site);
-    let call_site2 = enclosing_sp.ctxt.outer().expn_info().map(|ei| ei.call_site);
+    let call_site1 = sp.ctxt().outer().expn_info().map(|ei| ei.call_site);
+    let call_site2 = enclosing_sp.ctxt().outer().expn_info().map(|ei| ei.call_site);
     match (call_site1, call_site2) {
         (None, _) => sp,
         (Some(call_site1), Some(call_site2)) if call_site1 == call_site2 => sp,
@@ -232,7 +232,7 @@ impl CodeMap {
     }
 
     pub fn mk_substr_filename(&self, sp: Span) -> String {
-        let pos = self.lookup_char_pos(sp.lo);
+        let pos = self.lookup_char_pos(sp.lo());
         (format!("<{}:{}:{}>",
                  pos.file.name,
                  pos.line,
@@ -299,18 +299,16 @@ impl CodeMap {
     ///    * the lhs span needs to end on the same line the rhs span begins
     ///    * the lhs span must start at or before the rhs span
     pub fn merge_spans(&self, sp_lhs: Span, sp_rhs: Span) -> Option<Span> {
-        use std::cmp;
-
         // make sure we're at the same expansion id
-        if sp_lhs.ctxt != sp_rhs.ctxt {
+        if sp_lhs.ctxt() != sp_rhs.ctxt() {
             return None;
         }
 
-        let lhs_end = match self.lookup_line(sp_lhs.hi) {
+        let lhs_end = match self.lookup_line(sp_lhs.hi()) {
             Ok(x) => x,
             Err(_) => return None
         };
-        let rhs_begin = match self.lookup_line(sp_rhs.lo) {
+        let rhs_begin = match self.lookup_line(sp_rhs.lo()) {
             Ok(x) => x,
             Err(_) => return None
         };
@@ -321,12 +319,8 @@ impl CodeMap {
         }
 
         // ensure these follow the expected order and we don't overlap
-        if (sp_lhs.lo <= sp_rhs.lo) && (sp_lhs.hi <= sp_rhs.lo) {
-            Some(Span {
-                lo: cmp::min(sp_lhs.lo, sp_rhs.lo),
-                hi: cmp::max(sp_lhs.hi, sp_rhs.hi),
-                ctxt: sp_lhs.ctxt,
-            })
+        if (sp_lhs.lo() <= sp_rhs.lo()) && (sp_lhs.hi() <= sp_rhs.lo()) {
+            Some(sp_lhs.to(sp_rhs))
         } else {
             None
         }
@@ -337,8 +331,8 @@ impl CodeMap {
             return "no-location".to_string();
         }
 
-        let lo = self.lookup_char_pos_adj(sp.lo);
-        let hi = self.lookup_char_pos_adj(sp.hi);
+        let lo = self.lookup_char_pos_adj(sp.lo());
+        let hi = self.lookup_char_pos_adj(sp.hi());
         return (format!("{}:{}:{}: {}:{}",
                         lo.filename,
                         lo.line,
@@ -348,19 +342,19 @@ impl CodeMap {
     }
 
     pub fn span_to_filename(&self, sp: Span) -> FileName {
-        self.lookup_char_pos(sp.lo).file.name.to_string()
+        self.lookup_char_pos(sp.lo()).file.name.to_string()
     }
 
     pub fn span_to_lines(&self, sp: Span) -> FileLinesResult {
         debug!("span_to_lines(sp={:?})", sp);
 
-        if sp.lo > sp.hi {
+        if sp.lo() > sp.hi() {
             return Err(SpanLinesError::IllFormedSpan(sp));
         }
 
-        let lo = self.lookup_char_pos(sp.lo);
+        let lo = self.lookup_char_pos(sp.lo());
         debug!("span_to_lines: lo={:?}", lo);
-        let hi = self.lookup_char_pos(sp.hi);
+        let hi = self.lookup_char_pos(sp.hi());
         debug!("span_to_lines: hi={:?}", hi);
 
         if lo.file.start_pos != hi.file.start_pos {
@@ -400,12 +394,12 @@ impl CodeMap {
     }
 
     pub fn span_to_snippet(&self, sp: Span) -> Result<String, SpanSnippetError> {
-        if sp.lo > sp.hi {
+        if sp.lo() > sp.hi() {
             return Err(SpanSnippetError::IllFormedSpan(sp));
         }
 
-        let local_begin = self.lookup_byte_offset(sp.lo);
-        let local_end = self.lookup_byte_offset(sp.hi);
+        let local_begin = self.lookup_byte_offset(sp.lo());
+        let local_end = self.lookup_byte_offset(sp.hi());
 
         if local_begin.fm.start_pos != local_end.fm.start_pos {
             return Err(SpanSnippetError::DistinctSources(DistinctSources {
@@ -450,7 +444,7 @@ impl CodeMap {
             Ok(snippet) => {
                 let snippet = snippet.split(c).nth(0).unwrap_or("").trim_right();
                 if !snippet.is_empty() && !snippet.contains('\n') {
-                    Span { hi: BytePos(sp.lo.0 + snippet.len() as u32), ..sp }
+                    sp.with_hi(BytePos(sp.lo().0 + snippet.len() as u32))
                 } else {
                     sp
                 }
@@ -752,7 +746,7 @@ mod tests {
     fn t7() {
         // Test span_to_lines for a span ending at the end of filemap
         let cm = init_code_map();
-        let span = Span {lo: BytePos(12), hi: BytePos(23), ctxt: NO_EXPANSION};
+        let span = Span::new(BytePos(12), BytePos(23), NO_EXPANSION);
         let file_lines = cm.span_to_lines(span).unwrap();
 
         assert_eq!(file_lines.file.name, "blork.rs");
@@ -768,7 +762,7 @@ mod tests {
         assert_eq!(input.len(), selection.len());
         let left_index = selection.find('~').unwrap() as u32;
         let right_index = selection.rfind('~').map(|x|x as u32).unwrap_or(left_index);
-        Span { lo: BytePos(left_index), hi: BytePos(right_index + 1), ctxt: NO_EXPANSION }
+        Span::new(BytePos(left_index), BytePos(right_index + 1), NO_EXPANSION)
     }
 
     /// Test span_to_snippet and span_to_lines for a span converting 3
@@ -798,7 +792,7 @@ mod tests {
     fn t8() {
         // Test span_to_snippet for a span ending at the end of filemap
         let cm = init_code_map();
-        let span = Span {lo: BytePos(12), hi: BytePos(23), ctxt: NO_EXPANSION};
+        let span = Span::new(BytePos(12), BytePos(23), NO_EXPANSION);
         let snippet = cm.span_to_snippet(span);
 
         assert_eq!(snippet, Ok("second line".to_string()));
@@ -808,7 +802,7 @@ mod tests {
     fn t9() {
         // Test span_to_str for a span ending at the end of filemap
         let cm = init_code_map();
-        let span = Span {lo: BytePos(12), hi: BytePos(23), ctxt: NO_EXPANSION};
+        let span = Span::new(BytePos(12), BytePos(23), NO_EXPANSION);
         let sstr =  cm.span_to_string(span);
 
         assert_eq!(sstr, "blork.rs:2:1: 2:12");
@@ -859,11 +853,11 @@ mod tests {
                 let lo = hi + offset;
                 hi = lo + substring.len();
                 if i == n {
-                    let span = Span {
-                        lo: BytePos(lo as u32 + file.start_pos.0),
-                        hi: BytePos(hi as u32 + file.start_pos.0),
-                        ctxt: NO_EXPANSION,
-                    };
+                    let span = Span::new(
+                        BytePos(lo as u32 + file.start_pos.0),
+                        BytePos(hi as u32 + file.start_pos.0),
+                        NO_EXPANSION,
+                    );
                     assert_eq!(&self.span_to_snippet(span).unwrap()[..],
                             substring);
                     return span;
diff --git a/src/libsyntax/config.rs b/src/libsyntax/config.rs
index 14f1f8fbf8cb0..0909eec62691b 100644
--- a/src/libsyntax/config.rs
+++ b/src/libsyntax/config.rs
@@ -14,7 +14,6 @@ use {fold, attr};
 use ast;
 use codemap::Spanned;
 use parse::{token, ParseSess};
-use syntax_pos::Span;
 
 use ptr::P;
 use util::small_vector::SmallVector;
@@ -89,10 +88,10 @@ impl<'a> StripUnconfigured<'a> {
             parser.expect(&token::OpenDelim(token::Paren))?;
             let cfg = parser.parse_meta_item()?;
             parser.expect(&token::Comma)?;
-            let lo = parser.span.lo;
+            let lo = parser.span.lo();
             let (path, tokens) = parser.parse_path_and_tokens()?;
             parser.expect(&token::CloseDelim(token::Paren))?;
-            Ok((cfg, path, tokens, Span { lo: lo, ..parser.prev_span }))
+            Ok((cfg, path, tokens, parser.prev_span.with_lo(lo)))
         }) {
             Ok(result) => result,
             Err(mut e) => {
diff --git a/src/libsyntax/diagnostics/metadata.rs b/src/libsyntax/diagnostics/metadata.rs
index 5bbd18bd9ee2e..daa7112235f47 100644
--- a/src/libsyntax/diagnostics/metadata.rs
+++ b/src/libsyntax/diagnostics/metadata.rs
@@ -47,7 +47,7 @@ pub struct ErrorLocation {
 impl ErrorLocation {
     /// Create an error location from a span.
     pub fn from_span(ecx: &ExtCtxt, sp: Span) -> ErrorLocation {
-        let loc = ecx.codemap().lookup_char_pos_adj(sp.lo);
+        let loc = ecx.codemap().lookup_char_pos_adj(sp.lo());
         ErrorLocation {
             filename: loc.filename,
             line: loc.line
diff --git a/src/libsyntax/ext/base.rs b/src/libsyntax/ext/base.rs
index e57d9c6fe896a..cac2ff975d64b 100644
--- a/src/libsyntax/ext/base.rs
+++ b/src/libsyntax/ext/base.rs
@@ -731,7 +731,7 @@ impl<'a> ExtCtxt<'a> {
                     // Stop going up the backtrace once include! is encountered
                     return None;
                 }
-                ctxt = info.call_site.ctxt;
+                ctxt = info.call_site.ctxt();
                 last_macro = Some(info.call_site);
                 Some(())
             }).is_none() {
@@ -837,7 +837,7 @@ pub fn expr_to_spanned_string(cx: &mut ExtCtxt, expr: P<ast::Expr>, err_msg: &st
                               -> Option<Spanned<(Symbol, ast::StrStyle)>> {
     // Update `expr.span`'s ctxt now in case expr is an `include!` macro invocation.
     let expr = expr.map(|mut expr| {
-        expr.span.ctxt = expr.span.ctxt.apply_mark(cx.current_expansion.mark);
+        expr.span = expr.span.with_ctxt(expr.span.ctxt().apply_mark(cx.current_expansion.mark));
         expr
     });
 
diff --git a/src/libsyntax/ext/build.rs b/src/libsyntax/ext/build.rs
index cbdd00135930e..48d789372a07b 100644
--- a/src/libsyntax/ext/build.rs
+++ b/src/libsyntax/ext/build.rs
@@ -755,7 +755,7 @@ impl<'a> AstBuilder for ExtCtxt<'a> {
     }
 
     fn expr_fail(&self, span: Span, msg: Symbol) -> P<ast::Expr> {
-        let loc = self.codemap().lookup_char_pos(span.lo);
+        let loc = self.codemap().lookup_char_pos(span.lo());
         let expr_file = self.expr_str(span, Symbol::intern(&loc.file.name));
         let expr_line = self.expr_u32(span, loc.line as u32);
         let expr_col = self.expr_u32(span, loc.col.to_usize() as u32 + 1);
@@ -878,7 +878,8 @@ impl<'a> AstBuilder for ExtCtxt<'a> {
             attrs: vec![],
             pats,
             guard: None,
-            body: expr
+            body: expr,
+            beginning_vert: None,
         }
     }
 
diff --git a/src/libsyntax/ext/derive.rs b/src/libsyntax/ext/derive.rs
index 38715f7275de5..2e70962cad6f8 100644
--- a/src/libsyntax/ext/derive.rs
+++ b/src/libsyntax/ext/derive.rs
@@ -68,7 +68,7 @@ pub fn add_derived_markers<T>(cx: &mut ExtCtxt, span: Span, traits: &[ast::Path]
         },
     });
 
-    let span = Span { ctxt: cx.backtrace(), ..span };
+    let span = span.with_ctxt(cx.backtrace());
     item.map_attrs(|mut attrs| {
         if names.contains(&Symbol::intern("Eq")) && names.contains(&Symbol::intern("PartialEq")) {
             let meta = cx.meta_word(span, Symbol::intern("structural_match"));
diff --git a/src/libsyntax/ext/expand.rs b/src/libsyntax/ext/expand.rs
index d1172b1b2ce94..2f7d5685b6efe 100644
--- a/src/libsyntax/ext/expand.rs
+++ b/src/libsyntax/ext/expand.rs
@@ -598,7 +598,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
         match *ext {
             ProcMacroDerive(ref ext, _) => {
                 invoc.expansion_data.mark.set_expn_info(expn_info);
-                let span = Span { ctxt: self.cx.backtrace(), ..span };
+                let span = span.with_ctxt(self.cx.backtrace());
                 let dummy = ast::MetaItem { // FIXME(jseyfried) avoid this
                     name: keywords::Invalid.name(),
                     span: DUMMY_SP,
@@ -609,7 +609,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
             BuiltinDerive(func) => {
                 expn_info.callee.allow_internal_unstable = true;
                 invoc.expansion_data.mark.set_expn_info(expn_info);
-                let span = Span { ctxt: self.cx.backtrace(), ..span };
+                let span = span.with_ctxt(self.cx.backtrace());
                 let mut items = Vec::new();
                 func(self.cx, span, &attr.meta().unwrap(), &item, &mut |a| items.push(a));
                 kind.expect_from_annotatables(items)
@@ -684,8 +684,8 @@ impl<'a> Parser<'a> {
         if self.token != token::Eof {
             let msg = format!("macro expansion ignores token `{}` and any following",
                               self.this_token_to_string());
-            let mut def_site_span = self.span;
-            def_site_span.ctxt = SyntaxContext::empty(); // Avoid emitting backtrace info twice.
+            // Avoid emitting backtrace info twice.
+            let def_site_span = self.span.with_ctxt(SyntaxContext::empty());
             let mut err = self.diagnostic().struct_span_err(def_site_span, &msg);
             let msg = format!("caused by the macro expansion here; the usage \
                                of `{}!` is likely invalid in {} context",
@@ -1069,9 +1069,8 @@ impl Folder for Marker {
         ident
     }
 
-    fn new_span(&mut self, mut span: Span) -> Span {
-        span.ctxt = span.ctxt.apply_mark(self.0);
-        span
+    fn new_span(&mut self, span: Span) -> Span {
+        span.with_ctxt(span.ctxt().apply_mark(self.0))
     }
 
     fn fold_mac(&mut self, mac: ast::Mac) -> ast::Mac {
diff --git a/src/libsyntax/ext/source_util.rs b/src/libsyntax/ext/source_util.rs
index 95fe41be12254..18a262d139a27 100644
--- a/src/libsyntax/ext/source_util.rs
+++ b/src/libsyntax/ext/source_util.rs
@@ -36,7 +36,7 @@ pub fn expand_line(cx: &mut ExtCtxt, sp: Span, tts: &[tokenstream::TokenTree])
     base::check_zero_tts(cx, sp, tts, "line!");
 
     let topmost = cx.expansion_cause().unwrap_or(sp);
-    let loc = cx.codemap().lookup_char_pos(topmost.lo);
+    let loc = cx.codemap().lookup_char_pos(topmost.lo());
 
     base::MacEager::expr(cx.expr_u32(topmost, loc.line as u32))
 }
@@ -47,7 +47,7 @@ pub fn expand_column(cx: &mut ExtCtxt, sp: Span, tts: &[tokenstream::TokenTree])
     base::check_zero_tts(cx, sp, tts, "column!");
 
     let topmost = cx.expansion_cause().unwrap_or(sp);
-    let loc = cx.codemap().lookup_char_pos(topmost.lo);
+    let loc = cx.codemap().lookup_char_pos(topmost.lo());
 
     base::MacEager::expr(cx.expr_u32(topmost, loc.col.to_usize() as u32))
 }
@@ -70,7 +70,7 @@ pub fn expand_file(cx: &mut ExtCtxt, sp: Span, tts: &[tokenstream::TokenTree])
     base::check_zero_tts(cx, sp, tts, "file!");
 
     let topmost = cx.expansion_cause().unwrap_or(sp);
-    let loc = cx.codemap().lookup_char_pos(topmost.lo);
+    let loc = cx.codemap().lookup_char_pos(topmost.lo());
     base::MacEager::expr(cx.expr_str(topmost, Symbol::intern(&loc.file.name)))
 }
 
diff --git a/src/libsyntax/ext/tt/macro_parser.rs b/src/libsyntax/ext/tt/macro_parser.rs
index 405d06dafbfda..2167b64e6103d 100644
--- a/src/libsyntax/ext/tt/macro_parser.rs
+++ b/src/libsyntax/ext/tt/macro_parser.rs
@@ -329,7 +329,8 @@ fn inner_parse_loop(sess: &ParseSess,
                     // Only touch the binders we have actually bound
                     for idx in item.match_lo..item.match_hi {
                         let sub = item.matches[idx].clone();
-                        new_pos.push_match(idx, MatchedSeq(sub, Span { lo: item.sp_lo, ..span }));
+                        let span = span.with_lo(item.sp_lo);
+                        new_pos.push_match(idx, MatchedSeq(sub, span));
                     }
 
                     new_pos.match_cur = item.match_hi;
@@ -379,7 +380,7 @@ fn inner_parse_loop(sess: &ParseSess,
                         match_cur: item.match_cur,
                         match_hi: item.match_cur + seq.num_captures,
                         up: Some(item),
-                        sp_lo: sp.lo,
+                        sp_lo: sp.lo(),
                         top_elts: Tt(TokenTree::Sequence(sp, seq)),
                     }));
                 }
@@ -424,7 +425,7 @@ pub fn parse(sess: &ParseSess,
              recurse_into_modules: bool)
              -> NamedParseResult {
     let mut parser = Parser::new(sess, tts, directory, recurse_into_modules, true);
-    let mut cur_items = SmallVector::one(initial_matcher_pos(ms.to_owned(), parser.span.lo));
+    let mut cur_items = SmallVector::one(initial_matcher_pos(ms.to_owned(), parser.span.lo()));
     let mut next_items = Vec::new(); // or proceed normally
 
     loop {
diff --git a/src/libsyntax/ext/tt/macro_rules.rs b/src/libsyntax/ext/tt/macro_rules.rs
index 983b19c5bf073..6d58af497f091 100644
--- a/src/libsyntax/ext/tt/macro_rules.rs
+++ b/src/libsyntax/ext/tt/macro_rules.rs
@@ -130,7 +130,7 @@ fn generic_extension<'cx>(cx: &'cx mut ExtCtxt,
                     tts = tts.map_enumerated(|i, tt| {
                         let mut tt = tt.clone();
                         let mut sp = rhs_spans[i];
-                        sp.ctxt = tt.span().ctxt;
+                        sp = sp.with_ctxt(tt.span().ctxt());
                         tt.set_span(sp);
                         tt
                     });
@@ -161,7 +161,7 @@ fn generic_extension<'cx>(cx: &'cx mut ExtCtxt,
                     macro_ident: name
                 })
             }
-            Failure(sp, tok) => if sp.lo >= best_fail_spot.lo {
+            Failure(sp, tok) => if sp.lo() >= best_fail_spot.lo() {
                 best_fail_spot = sp;
                 best_fail_tok = Some(tok);
             },
diff --git a/src/libsyntax/ext/tt/quoted.rs b/src/libsyntax/ext/tt/quoted.rs
index 012d4a54b36f7..0e21e3f6b0010 100644
--- a/src/libsyntax/ext/tt/quoted.rs
+++ b/src/libsyntax/ext/tt/quoted.rs
@@ -37,7 +37,7 @@ impl Delimited {
         let open_span = if span == DUMMY_SP {
             DUMMY_SP
         } else {
-            Span { hi: span.lo + BytePos(self.delim.len() as u32), ..span }
+            span.with_lo(span.lo() + BytePos(self.delim.len() as u32))
         };
         TokenTree::Token(open_span, self.open_token())
     }
@@ -46,7 +46,7 @@ impl Delimited {
         let close_span = if span == DUMMY_SP {
             DUMMY_SP
         } else {
-            Span { lo: span.hi - BytePos(self.delim.len() as u32), ..span }
+            span.with_lo(span.hi() - BytePos(self.delim.len() as u32))
         };
         TokenTree::Token(close_span, self.close_token())
     }
@@ -152,7 +152,7 @@ pub fn parse(input: tokenstream::TokenStream, expect_matchers: bool, sess: &Pars
                     Some(tokenstream::TokenTree::Token(span, token::Colon)) => match trees.next() {
                         Some(tokenstream::TokenTree::Token(end_sp, ref tok)) => match tok.ident() {
                             Some(kind) => {
-                                let span = Span { lo: start_sp.lo, ..end_sp };
+                                let span = end_sp.with_lo(start_sp.lo());
                                 result.push(TokenTree::MetaVarDecl(span, ident, kind));
                                 continue
                             }
@@ -198,7 +198,7 @@ fn parse_tree<I>(tree: tokenstream::TokenTree,
             }
             Some(tokenstream::TokenTree::Token(ident_span, ref token)) if token.is_ident() => {
                 let ident = token.ident().unwrap();
-                let span = Span { lo: span.lo, ..ident_span };
+                let span = ident_span.with_lo(span.lo());
                 if ident.name == keywords::Crate.name() {
                     let ident = ast::Ident { name: keywords::DollarCrate.name(), ..ident };
                     TokenTree::Token(span, token::Ident(ident))
diff --git a/src/libsyntax/ext/tt/transcribe.rs b/src/libsyntax/ext/tt/transcribe.rs
index fe3dd83f9d5c0..d51b0d0ae3e93 100644
--- a/src/libsyntax/ext/tt/transcribe.rs
+++ b/src/libsyntax/ext/tt/transcribe.rs
@@ -155,7 +155,7 @@ pub fn transcribe(cx: &ExtCtxt,
                         if let NtTT(ref tt) = **nt {
                             result.push(tt.clone().into());
                         } else {
-                            sp.ctxt = sp.ctxt.apply_mark(cx.current_expansion.mark);
+                            sp = sp.with_ctxt(sp.ctxt().apply_mark(cx.current_expansion.mark));
                             let token = TokenTree::Token(sp, Token::interpolated((**nt).clone()));
                             result.push(token.into());
                         }
@@ -166,13 +166,13 @@ pub fn transcribe(cx: &ExtCtxt,
                 } else {
                     let ident =
                         Ident { ctxt: ident.ctxt.apply_mark(cx.current_expansion.mark), ..ident };
-                    sp.ctxt = sp.ctxt.apply_mark(cx.current_expansion.mark);
+                    sp = sp.with_ctxt(sp.ctxt().apply_mark(cx.current_expansion.mark));
                     result.push(TokenTree::Token(sp, token::Dollar).into());
                     result.push(TokenTree::Token(sp, token::Ident(ident)).into());
                 }
             }
             quoted::TokenTree::Delimited(mut span, delimited) => {
-                span.ctxt = span.ctxt.apply_mark(cx.current_expansion.mark);
+                span = span.with_ctxt(span.ctxt().apply_mark(cx.current_expansion.mark));
                 stack.push(Frame::Delimited { forest: delimited, idx: 0, span: span });
                 result_stack.push(mem::replace(&mut result, Vec::new()));
             }
diff --git a/src/libsyntax/feature_gate.rs b/src/libsyntax/feature_gate.rs
index 09574d5ba129e..54d41a030fd77 100644
--- a/src/libsyntax/feature_gate.rs
+++ b/src/libsyntax/feature_gate.rs
@@ -366,6 +366,10 @@ declare_features! (
     // Allows unsized tuple coercion.
     (active, unsized_tuple_coercion, "1.20.0", Some(42877)),
 
+    // Generators
+    (active, generators, "1.21.0", None),
+
+
     // global allocators and their internals
     (active, global_allocator, "1.20.0", None),
     (active, allocator_internals, "1.20.0", None),
@@ -375,6 +379,9 @@ declare_features! (
 
     // allow `#[must_use]` on functions (RFC 1940)
     (active, fn_must_use, "1.21.0", Some(43302)),
+
+    // allow '|' at beginning of match arms (RFC 1925)
+    (active, match_beginning_vert, "1.21.0", Some(44101)),
 );
 
 declare_features! (
@@ -1248,8 +1255,8 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
     fn visit_item(&mut self, i: &'a ast::Item) {
         match i.node {
             ast::ItemKind::ExternCrate(_) => {
-                if attr::contains_name(&i.attrs[..], "macro_reexport") {
-                    gate_feature_post!(&self, macro_reexport, i.span,
+                if let Some(attr) = attr::find_by_name(&i.attrs[..], "macro_reexport") {
+                    gate_feature_post!(&self, macro_reexport, attr.span,
                                        "macros reexports are experimental \
                                         and possibly buggy");
                 }
@@ -1276,36 +1283,32 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
                                         function may change over time, for now \
                                         a top-level `fn main()` is required");
                 }
-                if attr::contains_name(&i.attrs[..], "must_use") {
-                    gate_feature_post!(&self, fn_must_use, i.span,
+                if let Some(attr) = attr::find_by_name(&i.attrs[..], "must_use") {
+                    gate_feature_post!(&self, fn_must_use, attr.span,
                                        "`#[must_use]` on functions is experimental",
                                        GateStrength::Soft);
                 }
             }
 
             ast::ItemKind::Struct(..) => {
-                if attr::contains_name(&i.attrs[..], "simd") {
-                    gate_feature_post!(&self, simd, i.span,
+                if let Some(attr) = attr::find_by_name(&i.attrs[..], "simd") {
+                    gate_feature_post!(&self, simd, attr.span,
                                        "SIMD types are experimental and possibly buggy");
-                    self.context.parse_sess.span_diagnostic.span_warn(i.span,
+                    self.context.parse_sess.span_diagnostic.span_warn(attr.span,
                                                                       "the `#[simd]` attribute \
                                                                        is deprecated, use \
                                                                        `#[repr(simd)]` instead");
                 }
-                for attr in &i.attrs {
-                    if attr.path == "repr" {
-                        for item in attr.meta_item_list().unwrap_or_else(Vec::new) {
-                            if item.check_name("simd") {
-                                gate_feature_post!(&self, repr_simd, i.span,
-                                                   "SIMD types are experimental \
-                                                    and possibly buggy");
-
-                            }
-                            if item.check_name("align") {
-                                gate_feature_post!(&self, repr_align, i.span,
-                                                   "the struct `#[repr(align(u16))]` attribute \
-                                                    is experimental");
-                            }
+                if let Some(attr) = attr::find_by_name(&i.attrs[..], "repr") {
+                    for item in attr.meta_item_list().unwrap_or_else(Vec::new) {
+                        if item.check_name("simd") {
+                            gate_feature_post!(&self, repr_simd, attr.span,
+                                               "SIMD types are experimental and possibly buggy");
+                        }
+                        if item.check_name("align") {
+                            gate_feature_post!(&self, repr_align, attr.span,
+                                               "the struct `#[repr(align(u16))]` attribute \
+                                                is experimental");
                         }
                     }
                 }
@@ -1334,8 +1337,8 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
 
                 for impl_item in impl_items {
                     if let ast::ImplItemKind::Method(..) = impl_item.node {
-                        if attr::contains_name(&impl_item.attrs[..], "must_use") {
-                            gate_feature_post!(&self, fn_must_use, impl_item.span,
+                        if let Some(attr) = attr::find_by_name(&impl_item.attrs[..], "must_use") {
+                            gate_feature_post!(&self, fn_must_use, attr.span,
                                                "`#[must_use]` on methods is experimental",
                                                GateStrength::Soft);
                         }
@@ -1410,6 +1413,11 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
             ast::ExprKind::InPlace(..) => {
                 gate_feature_post!(&self, placement_in_syntax, e.span, EXPLAIN_PLACEMENT_IN);
             }
+            ast::ExprKind::Yield(..) => {
+                gate_feature_post!(&self, generators,
+                                  e.span,
+                                  "yield syntax is experimental");
+            }
             ast::ExprKind::Lit(ref lit) => {
                 if let ast::LitKind::Int(_, ref ty) = lit.node {
                     match *ty {
@@ -1430,6 +1438,15 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
         visit::walk_expr(self, e);
     }
 
+    fn visit_arm(&mut self, arm: &'a ast::Arm) {
+        if let Some(span) = arm.beginning_vert {
+            gate_feature_post!(&self, match_beginning_vert,
+                               span,
+                               "Use of a '|' at the beginning of a match arm is experimental")
+        }
+        visit::walk_arm(self, arm)
+    }
+
     fn visit_pat(&mut self, pattern: &'a ast::Pat) {
         match pattern.node {
             PatKind::Slice(_, Some(_), ref last) if !last.is_empty() => {
diff --git a/src/libsyntax/fold.rs b/src/libsyntax/fold.rs
index 6fd0a2eab4235..03c47b71d02d7 100644
--- a/src/libsyntax/fold.rs
+++ b/src/libsyntax/fold.rs
@@ -344,12 +344,14 @@ pub fn fold_thin_attrs<T: Folder>(attrs: ThinVec<Attribute>, fld: &mut T) -> Thi
     fold_attrs(attrs.into(), fld).into()
 }
 
-pub fn noop_fold_arm<T: Folder>(Arm {attrs, pats, guard, body}: Arm, fld: &mut T) -> Arm {
+pub fn noop_fold_arm<T: Folder>(Arm {attrs, pats, guard, body, beginning_vert}: Arm,
+    fld: &mut T) -> Arm {
     Arm {
         attrs: fold_attrs(attrs, fld),
         pats: pats.move_map(|x| fld.fold_pat(x)),
         guard: guard.map(|x| fld.fold_expr(x)),
         body: fld.fold_expr(body),
+        beginning_vert,
     }
 }
 
@@ -1311,6 +1313,7 @@ pub fn noop_fold_expr<T: Folder>(Expr {id, node, span, attrs}: Expr, folder: &mu
                     attrs: fold_attrs(attrs.into(), folder).into(),
                 };
             }
+            ExprKind::Yield(ex) => ExprKind::Yield(ex.map(|x| folder.fold_expr(x))),
             ExprKind::Try(ex) => ExprKind::Try(folder.fold_expr(ex)),
             ExprKind::Catch(body) => ExprKind::Catch(folder.fold_block(body)),
         },
diff --git a/src/libsyntax/json.rs b/src/libsyntax/json.rs
index 37a59411c1618..db49ab1034358 100644
--- a/src/libsyntax/json.rs
+++ b/src/libsyntax/json.rs
@@ -230,8 +230,8 @@ impl DiagnosticSpan {
                       mut backtrace: vec::IntoIter<MacroBacktrace>,
                       je: &JsonEmitter)
                       -> DiagnosticSpan {
-        let start = je.cm.lookup_char_pos(span.lo);
-        let end = je.cm.lookup_char_pos(span.hi);
+        let start = je.cm.lookup_char_pos(span.lo());
+        let end = je.cm.lookup_char_pos(span.hi());
         let backtrace_step = backtrace.next().map(|bt| {
             let call_site =
                 Self::from_span_full(bt.call_site,
@@ -256,8 +256,8 @@ impl DiagnosticSpan {
         });
         DiagnosticSpan {
             file_name: start.file.name.clone(),
-            byte_start: span.lo.0 - start.file.start_pos.0,
-            byte_end: span.hi.0 - start.file.start_pos.0,
+            byte_start: span.lo().0 - start.file.start_pos.0,
+            byte_end: span.hi().0 - start.file.start_pos.0,
             line_start: start.line,
             line_end: end.line,
             column_start: start.col.0 + 1,
diff --git a/src/libsyntax/parse/lexer/comments.rs b/src/libsyntax/parse/lexer/comments.rs
index f65fffebe337a..fb558d1a58f85 100644
--- a/src/libsyntax/parse/lexer/comments.rs
+++ b/src/libsyntax/parse/lexer/comments.rs
@@ -386,7 +386,7 @@ pub fn gather_comments_and_literals(sess: &ParseSess, path: String, srdr: &mut R
                 debug!("tok lit: {}", s);
                 literals.push(Literal {
                     lit: s.to_string(),
-                    pos: sp.lo,
+                    pos: sp.lo(),
                 });
             })
         } else {
diff --git a/src/libsyntax/parse/lexer/mod.rs b/src/libsyntax/parse/lexer/mod.rs
index 527d2e413969e..f26a046090545 100644
--- a/src/libsyntax/parse/lexer/mod.rs
+++ b/src/libsyntax/parse/lexer/mod.rs
@@ -71,7 +71,7 @@ pub struct StringReader<'a> {
 
 impl<'a> StringReader<'a> {
     fn mk_sp(&self, lo: BytePos, hi: BytePos) -> Span {
-        unwrap_or!(self.override_span, Span { lo: lo, hi: hi, ctxt: NO_EXPANSION})
+        unwrap_or!(self.override_span, Span::new(lo, hi, NO_EXPANSION))
     }
 
     fn next_token(&mut self) -> TokenAndSpan where Self: Sized {
@@ -190,20 +190,20 @@ impl<'a> StringReader<'a> {
     }
 
     pub fn retokenize(sess: &'a ParseSess, mut span: Span) -> Self {
-        let begin = sess.codemap().lookup_byte_offset(span.lo);
-        let end = sess.codemap().lookup_byte_offset(span.hi);
+        let begin = sess.codemap().lookup_byte_offset(span.lo());
+        let end = sess.codemap().lookup_byte_offset(span.hi());
 
         // Make the range zero-length if the span is invalid.
-        if span.lo > span.hi || begin.fm.start_pos != end.fm.start_pos {
-            span.hi = span.lo;
+        if span.lo() > span.hi() || begin.fm.start_pos != end.fm.start_pos {
+            span = span.with_hi(span.lo());
         }
 
         let mut sr = StringReader::new_raw_internal(sess, begin.fm);
 
         // Seek the lexer to the right byte range.
         sr.save_new_lines_and_multibyte = false;
-        sr.next_pos = span.lo;
-        sr.terminator = Some(span.hi);
+        sr.next_pos = span.lo();
+        sr.terminator = Some(span.hi());
 
         sr.bump();
 
@@ -1745,11 +1745,7 @@ mod tests {
         let tok1 = string_reader.next_token();
         let tok2 = TokenAndSpan {
             tok: token::Ident(id),
-            sp: Span {
-                lo: BytePos(21),
-                hi: BytePos(23),
-                ctxt: NO_EXPANSION,
-            },
+            sp: Span::new(BytePos(21), BytePos(23), NO_EXPANSION),
         };
         assert_eq!(tok1, tok2);
         assert_eq!(string_reader.next_token().tok, token::Whitespace);
@@ -1759,11 +1755,7 @@ mod tests {
         let tok3 = string_reader.next_token();
         let tok4 = TokenAndSpan {
             tok: token::Ident(Ident::from_str("main")),
-            sp: Span {
-                lo: BytePos(24),
-                hi: BytePos(28),
-                ctxt: NO_EXPANSION,
-            },
+            sp: Span::new(BytePos(24), BytePos(28), NO_EXPANSION),
         };
         assert_eq!(tok3, tok4);
         // the lparen is already read:
@@ -1921,7 +1913,7 @@ mod tests {
         let mut lexer = setup(&cm, &sh, "// test\r\n/// test\r\n".to_string());
         let comment = lexer.next_token();
         assert_eq!(comment.tok, token::Comment);
-        assert_eq!((comment.sp.lo, comment.sp.hi), (BytePos(0), BytePos(7)));
+        assert_eq!((comment.sp.lo(), comment.sp.hi()), (BytePos(0), BytePos(7)));
         assert_eq!(lexer.next_token().tok, token::Whitespace);
         assert_eq!(lexer.next_token().tok,
                    token::DocComment(Symbol::intern("/// test")));
diff --git a/src/libsyntax/parse/lexer/tokentrees.rs b/src/libsyntax/parse/lexer/tokentrees.rs
index ad389ab510aaf..a2c81e2475428 100644
--- a/src/libsyntax/parse/lexer/tokentrees.rs
+++ b/src/libsyntax/parse/lexer/tokentrees.rs
@@ -11,7 +11,6 @@
 use print::pprust::token_to_string;
 use parse::lexer::StringReader;
 use parse::{token, PResult};
-use syntax_pos::Span;
 use tokenstream::{Delimited, TokenStream, TokenTree};
 
 impl<'a> StringReader<'a> {
@@ -20,7 +19,7 @@ impl<'a> StringReader<'a> {
         let mut tts = Vec::new();
         while self.token != token::Eof {
             let tree = self.parse_token_tree()?;
-            let is_joint = tree.span().hi == self.span.lo && token::is_op(&self.token);
+            let is_joint = tree.span().hi() == self.span.lo() && token::is_op(&self.token);
             tts.push(if is_joint { tree.joint() } else { tree.into() });
         }
         Ok(TokenStream::concat(tts))
@@ -40,7 +39,7 @@ impl<'a> StringReader<'a> {
                     return TokenStream::concat(tts);
                 }
             };
-            let is_joint = tree.span().hi == self.span.lo && token::is_op(&self.token);
+            let is_joint = tree.span().hi() == self.span.lo() && token::is_op(&self.token);
             tts.push(if is_joint { tree.joint() } else { tree.into() });
         }
     }
@@ -69,7 +68,7 @@ impl<'a> StringReader<'a> {
                 let tts = self.parse_token_trees_until_close_delim();
 
                 // Expand to cover the entire delimited token tree
-                let span = Span { hi: self.span.hi, ..pre_span };
+                let span = pre_span.with_hi(self.span.hi());
 
                 match self.token {
                     // Correct delimiter.
diff --git a/src/libsyntax/parse/lexer/unicode_chars.rs b/src/libsyntax/parse/lexer/unicode_chars.rs
index c36fdef2d4c1d..39b5482a066d4 100644
--- a/src/libsyntax/parse/lexer/unicode_chars.rs
+++ b/src/libsyntax/parse/lexer/unicode_chars.rs
@@ -340,7 +340,7 @@ pub fn check_for_substitution<'a>(reader: &StringReader<'a>,
     .iter()
     .find(|&&(c, _, _)| c == ch)
     .map(|&(_, u_name, ascii_char)| {
-        let span = Span { lo: reader.pos, hi: reader.next_pos, ctxt: NO_EXPANSION };
+        let span = Span::new(reader.pos, reader.next_pos, NO_EXPANSION);
         match ASCII_ARRAY.iter().find(|&&(c, _)| c == ascii_char) {
             Some(&(ascii_char, ascii_name)) => {
                 let msg =
diff --git a/src/libsyntax/parse/mod.rs b/src/libsyntax/parse/mod.rs
index 67b4954a8f15b..76a7e2923fc39 100644
--- a/src/libsyntax/parse/mod.rs
+++ b/src/libsyntax/parse/mod.rs
@@ -181,7 +181,7 @@ pub fn filemap_to_parser(sess: & ParseSess, filemap: Rc<FileMap>, ) -> Parser {
     let mut parser = stream_to_parser(sess, filemap_to_stream(sess, filemap, None));
 
     if parser.token == token::Eof && parser.span == syntax_pos::DUMMY_SP {
-        parser.span = Span { lo: end_pos, hi: end_pos, ctxt: NO_EXPANSION };
+        parser.span = Span::new(end_pos, end_pos, NO_EXPANSION);
     }
 
     parser
@@ -661,7 +661,7 @@ mod tests {
 
     // produce a syntax_pos::span
     fn sp(a: u32, b: u32) -> Span {
-        Span {lo: BytePos(a), hi: BytePos(b), ctxt: NO_EXPANSION}
+        Span::new(BytePos(a), BytePos(b), NO_EXPANSION)
     }
 
     fn str2seg(s: &str, lo: u32, hi: u32) -> ast::PathSegment {
@@ -976,7 +976,7 @@ mod tests {
 
         for &src in &srcs {
             let spans = get_spans_of_pat_idents(src);
-            let Span{ lo, hi, .. } = spans[0];
+            let (lo, hi) = (spans[0].lo(), spans[0].hi());
             assert!("self" == &src[lo.to_usize()..hi.to_usize()],
                     "\"{}\" != \"self\". src=\"{}\"",
                     &src[lo.to_usize()..hi.to_usize()], src)
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 90a635fdf44fe..1f033b25fe4f6 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -790,9 +790,8 @@ impl<'a> Parser<'a> {
                 Ok(())
             }
             token::AndAnd => {
-                let span = self.span;
-                let lo = span.lo + BytePos(1);
-                Ok(self.bump_with(token::BinOp(token::And), Span { lo: lo, ..span }))
+                let span = self.span.with_lo(self.span.lo() + BytePos(1));
+                Ok(self.bump_with(token::BinOp(token::And), span))
             }
             _ => self.unexpected()
         }
@@ -824,9 +823,8 @@ impl<'a> Parser<'a> {
                 true
             }
             token::BinOp(token::Shl) => {
-                let span = self.span;
-                let lo = span.lo + BytePos(1);
-                self.bump_with(token::Lt, Span { lo: lo, ..span });
+                let span = self.span.with_lo(self.span.lo() + BytePos(1));
+                self.bump_with(token::Lt, span);
                 true
             }
             _ => false,
@@ -852,19 +850,16 @@ impl<'a> Parser<'a> {
                 Ok(())
             }
             token::BinOp(token::Shr) => {
-                let span = self.span;
-                let lo = span.lo + BytePos(1);
-                Ok(self.bump_with(token::Gt, Span { lo: lo, ..span }))
+                let span = self.span.with_lo(self.span.lo() + BytePos(1));
+                Ok(self.bump_with(token::Gt, span))
             }
             token::BinOpEq(token::Shr) => {
-                let span = self.span;
-                let lo = span.lo + BytePos(1);
-                Ok(self.bump_with(token::Ge, Span { lo: lo, ..span }))
+                let span = self.span.with_lo(self.span.lo() + BytePos(1));
+                Ok(self.bump_with(token::Ge, span))
             }
             token::Ge => {
-                let span = self.span;
-                let lo = span.lo + BytePos(1);
-                Ok(self.bump_with(token::Eq, Span { lo: lo, ..span }))
+                let span = self.span.with_lo(self.span.lo() + BytePos(1));
+                Ok(self.bump_with(token::Eq, span))
             }
             _ => self.unexpected()
         }
@@ -1094,7 +1089,7 @@ impl<'a> Parser<'a> {
     /// Advance the parser using provided token as a next one. Use this when
     /// consuming a part of a token. For example a single `<` from `<<`.
     pub fn bump_with(&mut self, next: token::Token, span: Span) {
-        self.prev_span = Span { hi: span.lo, ..self.span };
+        self.prev_span = self.span.with_hi(span.lo());
         // It would be incorrect to record the kind of the current token, but
         // fortunately for tokens currently using `bump_with`, the
         // prev_token_kind will be of no use anyway.
@@ -1356,7 +1351,7 @@ impl<'a> Parser<'a> {
         if self.eat(&token::RArrow) {
             Ok(FunctionRetTy::Ty(self.parse_ty_no_plus()?))
         } else {
-            Ok(FunctionRetTy::Default(Span { hi: self.span.lo, ..self.span }))
+            Ok(FunctionRetTy::Default(self.span.with_hi(self.span.lo())))
         }
     }
 
@@ -2222,6 +2217,14 @@ impl<'a> Parser<'a> {
                     };
                     ex = ExprKind::Break(lt, e);
                     hi = self.prev_span;
+                } else if self.eat_keyword(keywords::Yield) {
+                    if self.token.can_begin_expr() {
+                        let e = self.parse_expr()?;
+                        hi = e.span;
+                        ex = ExprKind::Yield(Some(e));
+                    } else {
+                        ex = ExprKind::Yield(None);
+                    }
                 } else if self.token.is_keyword(keywords::Let) {
                     // Catch this syntax error here, instead of in `parse_ident`, so
                     // that we can explicitly mention that let is not to be used as an expression
@@ -2524,7 +2527,7 @@ impl<'a> Parser<'a> {
 
     pub fn process_potential_macro_variable(&mut self) {
         let ident = match self.token {
-            token::Dollar if self.span.ctxt != syntax_pos::hygiene::SyntaxContext::empty() &&
+            token::Dollar if self.span.ctxt() != syntax_pos::hygiene::SyntaxContext::empty() &&
                              self.look_ahead(1, |t| t.is_ident()) => {
                 self.bump();
                 let name = match self.token { token::Ident(ident) => ident, _ => unreachable!() };
@@ -2726,8 +2729,8 @@ impl<'a> Parser<'a> {
                         err.span_label(self.span,
                                        "expecting a type here because of type ascription");
                         let cm = self.sess.codemap();
-                        let cur_pos = cm.lookup_char_pos(self.span.lo);
-                        let op_pos = cm.lookup_char_pos(cur_op_span.hi);
+                        let cur_pos = cm.lookup_char_pos(self.span.lo());
+                        let op_pos = cm.lookup_char_pos(cur_op_span.hi());
                         if cur_pos.line != op_pos.line {
                             err.span_suggestion_short(cur_op_span,
                                                       "did you mean to use `;` here?",
@@ -3022,7 +3025,10 @@ impl<'a> Parser<'a> {
         let decl = self.parse_fn_block_decl()?;
         let decl_hi = self.prev_span;
         let body = match decl.output {
-            FunctionRetTy::Default(_) => self.parse_expr()?,
+            FunctionRetTy::Default(_) => {
+                let restrictions = self.restrictions - RESTRICTION_STMT_EXPR;
+                self.parse_expr_res(restrictions, None)?
+            },
             _ => {
                 // If an explicit return type is given, require a
                 // block to appear (RFC 968).
@@ -3149,6 +3155,12 @@ impl<'a> Parser<'a> {
         maybe_whole!(self, NtArm, |x| x);
 
         let attrs = self.parse_outer_attributes()?;
+        // Allow a '|' before the pats (RFC 1925)
+        let beginning_vert = if self.eat(&token::BinOp(token::Or)) {
+            Some(self.prev_span)
+        } else {
+            None
+        };
         let pats = self.parse_pats()?;
         let guard = if self.eat_keyword(keywords::If) {
             Some(self.parse_expr()?)
@@ -3172,6 +3184,7 @@ impl<'a> Parser<'a> {
             pats,
             guard,
             body: expr,
+            beginning_vert,
         })
     }
 
@@ -4048,7 +4061,7 @@ impl<'a> Parser<'a> {
                     let mut stmt_span = stmt.span;
                     // expand the span to include the semicolon, if it exists
                     if self.eat(&token::Semi) {
-                        stmt_span.hi = self.prev_span.hi;
+                        stmt_span = stmt_span.with_hi(self.prev_span.hi());
                     }
                     let sugg = pprust::to_string(|s| {
                         use print::pprust::{PrintState, INDENT_UNIT};
@@ -4140,7 +4153,7 @@ impl<'a> Parser<'a> {
             stmt = stmt.add_trailing_semicolon();
         }
 
-        stmt.span.hi = self.prev_span.hi;
+        stmt.span = stmt.span.with_hi(self.prev_span.hi());
         Ok(Some(stmt))
     }
 
diff --git a/src/libsyntax/parse/token.rs b/src/libsyntax/parse/token.rs
index 834ac38af9870..d39f11bc3eef1 100644
--- a/src/libsyntax/parse/token.rs
+++ b/src/libsyntax/parse/token.rs
@@ -106,6 +106,7 @@ fn ident_can_begin_expr(ident: ast::Ident) -> bool {
         keywords::True.name(),
         keywords::Unsafe.name(),
         keywords::While.name(),
+        keywords::Yield.name(),
     ].contains(&ident.name)
 }
 
diff --git a/src/libsyntax/print/pprust.rs b/src/libsyntax/print/pprust.rs
index 3be831e828c72..3b5ec1caf0de9 100644
--- a/src/libsyntax/print/pprust.rs
+++ b/src/libsyntax/print/pprust.rs
@@ -603,8 +603,8 @@ pub trait PrintState<'a> {
     }
 
     fn print_literal(&mut self, lit: &ast::Lit) -> io::Result<()> {
-        self.maybe_print_comment(lit.span.lo)?;
-        if let Some(ltrl) = self.next_lit(lit.span.lo) {
+        self.maybe_print_comment(lit.span.lo())?;
+        if let Some(ltrl) = self.next_lit(lit.span.lo()) {
             return self.writer().word(&ltrl.lit);
         }
         match lit.node {
@@ -723,7 +723,7 @@ pub trait PrintState<'a> {
         if !is_inline {
             self.hardbreak_if_not_bol()?;
         }
-        self.maybe_print_comment(attr.span.lo)?;
+        self.maybe_print_comment(attr.span.lo())?;
         if attr.is_sugared_doc {
             self.writer().word(&attr.value_str().unwrap().as_str())?;
             self.writer().hardbreak()
@@ -892,7 +892,7 @@ impl<'a> State<'a> {
     }
     pub fn bclose_maybe_open(&mut self, span: syntax_pos::Span,
                              indented: usize, close_box: bool) -> io::Result<()> {
-        self.maybe_print_comment(span.hi)?;
+        self.maybe_print_comment(span.hi())?;
         self.break_offset_if_not_bol(1, -(indented as isize))?;
         self.s.word("}")?;
         if close_box {
@@ -950,13 +950,13 @@ impl<'a> State<'a> {
         let len = elts.len();
         let mut i = 0;
         for elt in elts {
-            self.maybe_print_comment(get_span(elt).hi)?;
+            self.maybe_print_comment(get_span(elt).hi())?;
             op(self, elt)?;
             i += 1;
             if i < len {
                 self.s.word(",")?;
                 self.maybe_print_trailing_comment(get_span(elt),
-                                                  Some(get_span(&elts[i]).hi))?;
+                                                  Some(get_span(&elts[i]).hi()))?;
                 self.space_if_not_bol()?;
             }
         }
@@ -996,7 +996,7 @@ impl<'a> State<'a> {
     }
 
     pub fn print_type(&mut self, ty: &ast::Ty) -> io::Result<()> {
-        self.maybe_print_comment(ty.span.lo)?;
+        self.maybe_print_comment(ty.span.lo())?;
         self.ibox(0)?;
         match ty.node {
             ast::TyKind::Slice(ref ty) => {
@@ -1094,7 +1094,7 @@ impl<'a> State<'a> {
     pub fn print_foreign_item(&mut self,
                               item: &ast::ForeignItem) -> io::Result<()> {
         self.hardbreak_if_not_bol()?;
-        self.maybe_print_comment(item.span.lo)?;
+        self.maybe_print_comment(item.span.lo())?;
         self.print_outer_attributes(&item.attrs)?;
         match item.node {
             ast::ForeignItemKind::Fn(ref decl, ref generics) => {
@@ -1163,7 +1163,7 @@ impl<'a> State<'a> {
     /// Pretty-print an item
     pub fn print_item(&mut self, item: &ast::Item) -> io::Result<()> {
         self.hardbreak_if_not_bol()?;
-        self.maybe_print_comment(item.span.lo)?;
+        self.maybe_print_comment(item.span.lo())?;
         self.print_outer_attributes(&item.attrs)?;
         self.ann.pre(self, NodeItem(item))?;
         match item.node {
@@ -1433,7 +1433,7 @@ impl<'a> State<'a> {
         self.bopen()?;
         for v in variants {
             self.space_if_not_bol()?;
-            self.maybe_print_comment(v.span.lo)?;
+            self.maybe_print_comment(v.span.lo())?;
             self.print_outer_attributes(&v.node.attrs)?;
             self.ibox(INDENT_UNIT)?;
             self.print_variant(v)?;
@@ -1481,7 +1481,7 @@ impl<'a> State<'a> {
                 self.commasep(
                     Inconsistent, struct_def.fields(),
                     |s, field| {
-                        s.maybe_print_comment(field.span.lo)?;
+                        s.maybe_print_comment(field.span.lo())?;
                         s.print_outer_attributes(&field.attrs)?;
                         s.print_visibility(&field.vis)?;
                         s.print_type(&field.ty)
@@ -1503,7 +1503,7 @@ impl<'a> State<'a> {
 
             for field in struct_def.fields() {
                 self.hardbreak_if_not_bol()?;
-                self.maybe_print_comment(field.span.lo)?;
+                self.maybe_print_comment(field.span.lo())?;
                 self.print_outer_attributes(&field.attrs)?;
                 self.print_visibility(&field.vis)?;
                 self.print_ident(field.ident.unwrap())?;
@@ -1548,7 +1548,7 @@ impl<'a> State<'a> {
                             -> io::Result<()> {
         self.ann.pre(self, NodeSubItem(ti.id))?;
         self.hardbreak_if_not_bol()?;
-        self.maybe_print_comment(ti.span.lo)?;
+        self.maybe_print_comment(ti.span.lo())?;
         self.print_outer_attributes(&ti.attrs)?;
         match ti.node {
             ast::TraitItemKind::Const(ref ty, ref default) => {
@@ -1590,7 +1590,7 @@ impl<'a> State<'a> {
     pub fn print_impl_item(&mut self, ii: &ast::ImplItem) -> io::Result<()> {
         self.ann.pre(self, NodeSubItem(ii.id))?;
         self.hardbreak_if_not_bol()?;
-        self.maybe_print_comment(ii.span.lo)?;
+        self.maybe_print_comment(ii.span.lo())?;
         self.print_outer_attributes(&ii.attrs)?;
         self.print_defaultness(ii.defaultness)?;
         match ii.node {
@@ -1622,7 +1622,7 @@ impl<'a> State<'a> {
     }
 
     pub fn print_stmt(&mut self, st: &ast::Stmt) -> io::Result<()> {
-        self.maybe_print_comment(st.span.lo)?;
+        self.maybe_print_comment(st.span.lo())?;
         match st.node {
             ast::StmtKind::Local(ref loc) => {
                 self.print_outer_attributes(&loc.attrs)?;
@@ -1705,7 +1705,7 @@ impl<'a> State<'a> {
             BlockCheckMode::Unsafe(..) => self.word_space("unsafe")?,
             BlockCheckMode::Default => ()
         }
-        self.maybe_print_comment(blk.span.lo)?;
+        self.maybe_print_comment(blk.span.lo())?;
         self.ann.pre(self, NodeBlock(blk))?;
         self.bopen()?;
 
@@ -1714,10 +1714,10 @@ impl<'a> State<'a> {
         for (i, st) in blk.stmts.iter().enumerate() {
             match st.node {
                 ast::StmtKind::Expr(ref expr) if i == blk.stmts.len() - 1 => {
-                    self.maybe_print_comment(st.span.lo)?;
+                    self.maybe_print_comment(st.span.lo())?;
                     self.space_if_not_bol()?;
                     self.print_expr_outer_attr_style(expr, false)?;
-                    self.maybe_print_trailing_comment(expr.span, Some(blk.span.hi))?;
+                    self.maybe_print_trailing_comment(expr.span, Some(blk.span.hi()))?;
                 }
                 _ => self.print_stmt(st)?,
             }
@@ -1988,7 +1988,7 @@ impl<'a> State<'a> {
     fn print_expr_outer_attr_style(&mut self,
                                   expr: &ast::Expr,
                                   is_inline: bool) -> io::Result<()> {
-        self.maybe_print_comment(expr.span.lo)?;
+        self.maybe_print_comment(expr.span.lo())?;
 
         let attrs = &expr.attrs;
         if is_inline {
@@ -2281,6 +2281,16 @@ impl<'a> State<'a> {
                 self.print_expr(e)?;
                 self.pclose()?;
             },
+            ast::ExprKind::Yield(ref e) => {
+                self.s.word("yield")?;
+                match *e {
+                    Some(ref expr) => {
+                        self.s.space()?;
+                        self.print_expr(&expr)?;
+                    }
+                    _ => ()
+                }
+            }
             ast::ExprKind::Try(ref e) => {
                 self.print_expr(e)?;
                 self.s.word("?")?
@@ -2333,7 +2343,7 @@ impl<'a> State<'a> {
                   defaults_to_global: bool)
                   -> io::Result<()>
     {
-        self.maybe_print_comment(path.span.lo)?;
+        self.maybe_print_comment(path.span.lo())?;
 
         let mut segments = path.segments[..path.segments.len()-depth].iter();
         if defaults_to_global && path.is_global() {
@@ -2455,7 +2465,7 @@ impl<'a> State<'a> {
     }
 
     pub fn print_pat(&mut self, pat: &ast::Pat) -> io::Result<()> {
-        self.maybe_print_comment(pat.span.lo)?;
+        self.maybe_print_comment(pat.span.lo())?;
         self.ann.pre(self, NodePat(pat))?;
         /* Pat isn't normalized, but the beauty of it
          is that it doesn't matter */
@@ -2597,7 +2607,7 @@ impl<'a> State<'a> {
         }
         self.cbox(INDENT_UNIT)?;
         self.ibox(0)?;
-        self.maybe_print_comment(arm.pats[0].span.lo)?;
+        self.maybe_print_comment(arm.pats[0].span.lo())?;
         self.print_outer_attributes(&arm.attrs)?;
         let mut first = true;
         for p in &arm.pats {
@@ -2705,7 +2715,7 @@ impl<'a> State<'a> {
         match decl.output {
             ast::FunctionRetTy::Ty(ref ty) => {
                 self.print_type(ty)?;
-                self.maybe_print_comment(ty.span.lo)
+                self.maybe_print_comment(ty.span.lo())
             }
             ast::FunctionRetTy::Default(..) => unreachable!(),
         }
@@ -2961,7 +2971,7 @@ impl<'a> State<'a> {
         self.end()?;
 
         match decl.output {
-            ast::FunctionRetTy::Ty(ref output) => self.maybe_print_comment(output.span.lo),
+            ast::FunctionRetTy::Ty(ref output) => self.maybe_print_comment(output.span.lo()),
             _ => Ok(())
         }
     }
@@ -3007,10 +3017,10 @@ impl<'a> State<'a> {
         };
         if let Some(ref cmnt) = self.next_comment() {
             if cmnt.style != comments::Trailing { return Ok(()) }
-            let span_line = cm.lookup_char_pos(span.hi);
+            let span_line = cm.lookup_char_pos(span.hi());
             let comment_line = cm.lookup_char_pos(cmnt.pos);
             let next = next_pos.unwrap_or(cmnt.pos + BytePos(1));
-            if span.hi < cmnt.pos && cmnt.pos < next && span_line.line == comment_line.line {
+            if span.hi() < cmnt.pos && cmnt.pos < next && span_line.line == comment_line.line {
                 self.print_comment(cmnt)?;
             }
         }
diff --git a/src/libsyntax/std_inject.rs b/src/libsyntax/std_inject.rs
index 8977d701e5a2b..7aa94de9d3d5b 100644
--- a/src/libsyntax/std_inject.rs
+++ b/src/libsyntax/std_inject.rs
@@ -31,7 +31,7 @@ fn ignored_span(sp: Span) -> Span {
             allow_internal_unsafe: false,
         }
     });
-    Span { ctxt: SyntaxContext::empty().apply_mark(mark), ..sp }
+    sp.with_ctxt(SyntaxContext::empty().apply_mark(mark))
 }
 
 pub fn injected_crate_name(krate: &ast::Crate) -> Option<&'static str> {
diff --git a/src/libsyntax/test.rs b/src/libsyntax/test.rs
index 35dc981952908..5a5a1ce3777e6 100644
--- a/src/libsyntax/test.rs
+++ b/src/libsyntax/test.rs
@@ -306,7 +306,7 @@ fn generate_test_harness(sess: &ParseSess,
 /// call to codemap's `is_internal` check.
 /// The expanded code calls some unstable functions in the test crate.
 fn ignored_span(cx: &TestCtxt, sp: Span) -> Span {
-    Span { ctxt: cx.ctxt, ..sp }
+    sp.with_ctxt(cx.ctxt)
 }
 
 #[derive(PartialEq)]
diff --git a/src/libsyntax/test_snippet.rs b/src/libsyntax/test_snippet.rs
index 4fae2ff9814fd..e9b1976ea472b 100644
--- a/src/libsyntax/test_snippet.rs
+++ b/src/libsyntax/test_snippet.rs
@@ -80,11 +80,7 @@ fn make_span(file_text: &str, start: &Position, end: &Position) -> Span {
     let start = make_pos(file_text, start);
     let end = make_pos(file_text, end) + end.string.len(); // just after matching thing ends
     assert!(start <= end);
-    Span {
-        lo: BytePos(start as u32),
-        hi: BytePos(end as u32),
-        ctxt: NO_EXPANSION,
-    }
+    Span::new(BytePos(start as u32), BytePos(end as u32), NO_EXPANSION)
 }
 
 fn make_pos(file_text: &str, pos: &Position) -> usize {
diff --git a/src/libsyntax/tokenstream.rs b/src/libsyntax/tokenstream.rs
index 747bc7b438554..870f54e4396af 100644
--- a/src/libsyntax/tokenstream.rs
+++ b/src/libsyntax/tokenstream.rs
@@ -59,7 +59,7 @@ impl Delimited {
         let open_span = if span == DUMMY_SP {
             DUMMY_SP
         } else {
-            Span { hi: span.lo + BytePos(self.delim.len() as u32), ..span }
+            span.with_hi(span.lo() + BytePos(self.delim.len() as u32))
         };
         TokenTree::Token(open_span, self.open_token())
     }
@@ -69,7 +69,7 @@ impl Delimited {
         let close_span = if span == DUMMY_SP {
             DUMMY_SP
         } else {
-            Span { lo: span.hi - BytePos(self.delim.len() as u32), ..span }
+            span.with_lo(span.hi() - BytePos(self.delim.len() as u32))
         };
         TokenTree::Token(close_span, self.close_token())
     }
@@ -602,11 +602,7 @@ mod tests {
     }
 
     fn sp(a: u32, b: u32) -> Span {
-        Span {
-            lo: BytePos(a),
-            hi: BytePos(b),
-            ctxt: NO_EXPANSION,
-        }
+        Span::new(BytePos(a), BytePos(b), NO_EXPANSION)
     }
 
     #[test]
diff --git a/src/libsyntax/visit.rs b/src/libsyntax/visit.rs
index f4ac7e341ce4b..05077d42a0bed 100644
--- a/src/libsyntax/visit.rs
+++ b/src/libsyntax/visit.rs
@@ -784,6 +784,9 @@ pub fn walk_expr<'a, V: Visitor<'a>>(visitor: &mut V, expression: &'a Expr) {
                 visitor.visit_expr(&output.expr)
             }
         }
+        ExprKind::Yield(ref optional_expression) => {
+            walk_list!(visitor, visit_expr, optional_expression);
+        }
         ExprKind::Try(ref subexpression) => {
             visitor.visit_expr(subexpression)
         }
diff --git a/src/libsyntax_ext/cfg.rs b/src/libsyntax_ext/cfg.rs
index 98da49545f927..1d8dc4064685b 100644
--- a/src/libsyntax_ext/cfg.rs
+++ b/src/libsyntax_ext/cfg.rs
@@ -24,6 +24,7 @@ pub fn expand_cfg<'cx>(cx: &mut ExtCtxt,
                        sp: Span,
                        tts: &[tokenstream::TokenTree])
                        -> Box<base::MacResult + 'static> {
+    let sp = sp.with_ctxt(sp.ctxt().apply_mark(cx.current_expansion.mark));
     let mut p = cx.new_parser_from_tts(tts);
     let cfg = panictry!(p.parse_meta_item());
 
diff --git a/src/libsyntax_ext/concat.rs b/src/libsyntax_ext/concat.rs
index bfe18dc4060c9..c79e7867c5f5e 100644
--- a/src/libsyntax_ext/concat.rs
+++ b/src/libsyntax_ext/concat.rs
@@ -57,5 +57,6 @@ pub fn expand_syntax_ext(cx: &mut base::ExtCtxt,
             }
         }
     }
+    let sp = sp.with_ctxt(sp.ctxt().apply_mark(cx.current_expansion.mark));
     base::MacEager::expr(cx.expr_str(sp, Symbol::intern(&accumulator)))
 }
diff --git a/src/libsyntax_ext/concat_idents.rs b/src/libsyntax_ext/concat_idents.rs
index 6f4c112acb6c6..8d0104e512bfb 100644
--- a/src/libsyntax_ext/concat_idents.rs
+++ b/src/libsyntax_ext/concat_idents.rs
@@ -92,6 +92,6 @@ pub fn expand_syntax_ext<'cx>(cx: &'cx mut ExtCtxt,
 
     Box::new(Result {
         ident: res,
-        span: sp,
+        span: sp.with_ctxt(sp.ctxt().apply_mark(cx.current_expansion.mark)),
     })
 }
diff --git a/src/libsyntax_ext/deriving/clone.rs b/src/libsyntax_ext/deriving/clone.rs
index 71dd7abfab04a..5d93c2a5f72a1 100644
--- a/src/libsyntax_ext/deriving/clone.rs
+++ b/src/libsyntax_ext/deriving/clone.rs
@@ -111,7 +111,7 @@ fn cs_clone_shallow(name: &str,
                         ty: P<ast::Ty>, span: Span, helper_name: &str) {
         // Generate statement `let _: helper_name<ty>;`,
         // set the expn ID so we can use the unstable struct.
-        let span = Span { ctxt: cx.backtrace(), ..span};
+        let span = span.with_ctxt(cx.backtrace());
         let assert_path = cx.path_all(span, true,
                                         cx.std_path(&["clone", helper_name]),
                                         vec![], vec![ty], vec![]);
diff --git a/src/libsyntax_ext/deriving/cmp/eq.rs b/src/libsyntax_ext/deriving/cmp/eq.rs
index 0b57beeae858b..a282ff5bd045f 100644
--- a/src/libsyntax_ext/deriving/cmp/eq.rs
+++ b/src/libsyntax_ext/deriving/cmp/eq.rs
@@ -58,7 +58,7 @@ fn cs_total_eq_assert(cx: &mut ExtCtxt, trait_span: Span, substr: &Substructure)
                         ty: P<ast::Ty>, span: Span, helper_name: &str) {
         // Generate statement `let _: helper_name<ty>;`,
         // set the expn ID so we can use the unstable struct.
-        let span = Span { ctxt: cx.backtrace(), ..span };
+        let span = span.with_ctxt(cx.backtrace());
         let assert_path = cx.path_all(span, true,
                                         cx.std_path(&["cmp", helper_name]),
                                         vec![], vec![ty], vec![]);
diff --git a/src/libsyntax_ext/deriving/debug.rs b/src/libsyntax_ext/deriving/debug.rs
index 54d71dd4b48e3..ab6dd04520c1b 100644
--- a/src/libsyntax_ext/deriving/debug.rs
+++ b/src/libsyntax_ext/deriving/debug.rs
@@ -67,7 +67,7 @@ fn show_substructure(cx: &mut ExtCtxt, span: Span, substr: &Substructure) -> P<E
     };
 
     // We want to make sure we have the ctxt set so that we can use unstable methods
-    let span = Span { ctxt: cx.backtrace(), ..span };
+    let span = span.with_ctxt(cx.backtrace());
     let name = cx.expr_lit(span, ast::LitKind::Str(ident.name, ast::StrStyle::Cooked));
     let builder = Ident::from_str("builder");
     let builder_expr = cx.expr_ident(span, builder.clone());
diff --git a/src/libsyntax_ext/deriving/generic/mod.rs b/src/libsyntax_ext/deriving/generic/mod.rs
index a0dd2975ca0c6..d701810e2e9f2 100644
--- a/src/libsyntax_ext/deriving/generic/mod.rs
+++ b/src/libsyntax_ext/deriving/generic/mod.rs
@@ -375,7 +375,7 @@ fn find_type_parameters(ty: &ast::Ty,
         }
 
         fn visit_mac(&mut self, mac: &ast::Mac) {
-            let span = Span { ctxt: self.span.ctxt, ..mac.span };
+            let span = mac.span.with_ctxt(self.span.ctxt());
             self.cx.span_err(span, "`derive` cannot be used on items with type macros");
         }
     }
@@ -1464,7 +1464,7 @@ impl<'a> MethodDef<'a> {
             .iter()
             .map(|v| {
                 let ident = v.node.name;
-                let sp = Span { ctxt: trait_.span.ctxt, ..v.span };
+                let sp = v.span.with_ctxt(trait_.span.ctxt());
                 let summary = trait_.summarise_struct(cx, &v.node.data);
                 (ident, sp, summary)
             })
@@ -1484,7 +1484,7 @@ impl<'a> TraitDef<'a> {
         let mut named_idents = Vec::new();
         let mut just_spans = Vec::new();
         for field in struct_def.fields() {
-            let sp = Span { ctxt: self.span.ctxt, ..field.span };
+            let sp = field.span.with_ctxt(self.span.ctxt());
             match field.ident {
                 Some(ident) => named_idents.push((ident, sp)),
                 _ => just_spans.push(sp),
@@ -1529,7 +1529,7 @@ impl<'a> TraitDef<'a> {
         let mut paths = Vec::new();
         let mut ident_exprs = Vec::new();
         for (i, struct_field) in struct_def.fields().iter().enumerate() {
-            let sp = Span { ctxt: self.span.ctxt, ..struct_field.span };
+            let sp = struct_field.span.with_ctxt(self.span.ctxt());
             let ident = cx.ident_of(&format!("{}_{}", prefix, i));
             paths.push(codemap::Spanned {
                 span: sp,
@@ -1550,7 +1550,7 @@ impl<'a> TraitDef<'a> {
                             cx.span_bug(sp, "a braced struct with unnamed fields in `derive`");
                         }
                         codemap::Spanned {
-                            span: Span { ctxt: self.span.ctxt, ..pat.span },
+                            span: pat.span.with_ctxt(self.span.ctxt()),
                             node: ast::FieldPat {
                                 ident: ident.unwrap(),
                                 pat,
@@ -1582,7 +1582,7 @@ impl<'a> TraitDef<'a> {
          mutbl: ast::Mutability)
          -> (P<ast::Pat>, Vec<(Span, Option<Ident>, P<Expr>, &'a [ast::Attribute])>) {
         let variant_ident = variant.node.name;
-        let sp = Span { ctxt: self.span.ctxt, ..variant.span };
+        let sp = variant.span.with_ctxt(self.span.ctxt());
         let variant_path = cx.path(sp, vec![enum_ident, variant_ident]);
         self.create_struct_pattern(cx, variant_path, &variant.node.data, prefix, mutbl)
     }
diff --git a/src/libsyntax_ext/deriving/mod.rs b/src/libsyntax_ext/deriving/mod.rs
index cd706f14a680d..ccf3d5502341f 100644
--- a/src/libsyntax_ext/deriving/mod.rs
+++ b/src/libsyntax_ext/deriving/mod.rs
@@ -158,13 +158,13 @@ fn call_intrinsic(cx: &ExtCtxt,
                   args: Vec<P<ast::Expr>>)
                   -> P<ast::Expr> {
     if cx.current_expansion.mark.expn_info().unwrap().callee.allow_internal_unstable {
-        span.ctxt = cx.backtrace();
+        span = span.with_ctxt(cx.backtrace());
     } else { // Avoid instability errors with user defined curstom derives, cc #36316
         let mut info = cx.current_expansion.mark.expn_info().unwrap();
         info.callee.allow_internal_unstable = true;
         let mark = Mark::fresh(Mark::root());
         mark.set_expn_info(info);
-        span.ctxt = SyntaxContext::empty().apply_mark(mark);
+        span = span.with_ctxt(SyntaxContext::empty().apply_mark(mark));
     }
     let path = cx.std_path(&["intrinsics", intrinsic]);
     let call = cx.expr_call_global(span, path, args);
diff --git a/src/libsyntax_ext/env.rs b/src/libsyntax_ext/env.rs
index affebbabbbda4..fcad065be52bc 100644
--- a/src/libsyntax_ext/env.rs
+++ b/src/libsyntax_ext/env.rs
@@ -32,6 +32,7 @@ pub fn expand_option_env<'cx>(cx: &'cx mut ExtCtxt,
         Some(v) => v,
     };
 
+    let sp = sp.with_ctxt(sp.ctxt().apply_mark(cx.current_expansion.mark));
     let e = match env::var(&*var.as_str()) {
         Err(..) => {
             cx.expr_path(cx.path_all(sp,
diff --git a/src/libsyntax_ext/format.rs b/src/libsyntax_ext/format.rs
index 764cedfcf2061..3e20bc481bde8 100644
--- a/src/libsyntax_ext/format.rs
+++ b/src/libsyntax_ext/format.rs
@@ -558,10 +558,8 @@ impl<'a, 'b> Context<'a, 'b> {
         // passed to this function.
         for (i, e) in self.args.into_iter().enumerate() {
             let name = self.ecx.ident_of(&format!("__arg{}", i));
-            let span = Span {
-                ctxt: e.span.ctxt.apply_mark(self.ecx.current_expansion.mark),
-                ..DUMMY_SP
-            };
+            let span =
+                DUMMY_SP.with_ctxt(e.span.ctxt().apply_mark(self.ecx.current_expansion.mark));
             pats.push(self.ecx.pat_ident(span, name));
             for ref arg_ty in self.arg_unique_types[i].iter() {
                 locals.push(Context::format_arg(self.ecx, self.macsp, e.span, arg_ty, name));
@@ -642,7 +640,7 @@ impl<'a, 'b> Context<'a, 'b> {
                   ty: &ArgumentType,
                   arg: ast::Ident)
                   -> P<ast::Expr> {
-        sp.ctxt = sp.ctxt.apply_mark(ecx.current_expansion.mark);
+        sp = sp.with_ctxt(sp.ctxt().apply_mark(ecx.current_expansion.mark));
         let arg = ecx.expr_ident(sp, arg);
         let trait_ = match *ty {
             Placeholder(ref tyname) => {
@@ -679,7 +677,7 @@ pub fn expand_format_args<'cx>(ecx: &'cx mut ExtCtxt,
                                mut sp: Span,
                                tts: &[tokenstream::TokenTree])
                                -> Box<base::MacResult + 'cx> {
-    sp.ctxt = sp.ctxt.apply_mark(ecx.current_expansion.mark);
+    sp = sp.with_ctxt(sp.ctxt().apply_mark(ecx.current_expansion.mark));
     match parse_args(ecx, sp, tts) {
         Some((efmt, args, names)) => {
             MacEager::expr(expand_preparsed_format_args(ecx, sp, efmt, args, names))
@@ -701,7 +699,7 @@ pub fn expand_preparsed_format_args(ecx: &mut ExtCtxt,
     let arg_types: Vec<_> = (0..args.len()).map(|_| Vec::new()).collect();
     let arg_unique_types: Vec<_> = (0..args.len()).map(|_| Vec::new()).collect();
     let mut macsp = ecx.call_site();
-    macsp.ctxt = macsp.ctxt.apply_mark(ecx.current_expansion.mark);
+    macsp = macsp.with_ctxt(macsp.ctxt().apply_mark(ecx.current_expansion.mark));
     let msg = "format argument must be a string literal.";
     let fmt = match expr_to_spanned_string(ecx, efmt, msg) {
         Some(fmt) => fmt,
diff --git a/src/libsyntax_ext/proc_macro_registrar.rs b/src/libsyntax_ext/proc_macro_registrar.rs
index a8a54a97ac368..a58d2c96388ca 100644
--- a/src/libsyntax_ext/proc_macro_registrar.rs
+++ b/src/libsyntax_ext/proc_macro_registrar.rs
@@ -371,7 +371,7 @@ fn mk_registrar(cx: &mut ExtCtxt,
             allow_internal_unsafe: false,
         }
     });
-    let span = Span { ctxt: SyntaxContext::empty().apply_mark(mark), ..DUMMY_SP };
+    let span = DUMMY_SP.with_ctxt(SyntaxContext::empty().apply_mark(mark));
 
     let proc_macro = Ident::from_str("proc_macro");
     let krate = cx.item(span,
diff --git a/src/libsyntax_pos/lib.rs b/src/libsyntax_pos/lib.rs
index d34dcfa3ed324..cba5c812b07ce 100644
--- a/src/libsyntax_pos/lib.rs
+++ b/src/libsyntax_pos/lib.rs
@@ -25,6 +25,7 @@
 #![feature(optin_builtin_traits)]
 #![allow(unused_attributes)]
 #![feature(specialization)]
+#![feature(staged_api)]
 
 use std::borrow::Cow;
 use std::cell::{Cell, RefCell};
@@ -60,13 +61,22 @@ pub type FileName = String;
 /// range between files.
 #[derive(Clone, Copy, Hash, PartialEq, Eq, Ord, PartialOrd)]
 pub struct Span {
+    #[unstable(feature = "rustc_private", issue = "27812")]
+    #[rustc_deprecated(since = "1.21", reason = "use getters/setters instead")]
     pub lo: BytePos,
+    #[unstable(feature = "rustc_private", issue = "27812")]
+    #[rustc_deprecated(since = "1.21", reason = "use getters/setters instead")]
     pub hi: BytePos,
     /// Information about where the macro came from, if this piece of
     /// code was created by a macro expansion.
+    #[unstable(feature = "rustc_private", issue = "27812")]
+    #[rustc_deprecated(since = "1.21", reason = "use getters/setters instead")]
     pub ctxt: SyntaxContext,
 }
 
+#[allow(deprecated)]
+pub const DUMMY_SP: Span = Span { lo: BytePos(0), hi: BytePos(0), ctxt: NO_EXPANSION };
+
 /// A collection of spans. Spans have two orthogonal attributes:
 ///
 /// - they can be *primary spans*. In this case they are the locus of
@@ -80,16 +90,50 @@ pub struct MultiSpan {
 }
 
 impl Span {
+    #[allow(deprecated)]
+    #[inline]
+    pub fn new(lo: BytePos, hi: BytePos, ctxt: SyntaxContext) -> Self {
+        if lo <= hi { Span { lo, hi, ctxt } } else { Span { lo: hi, hi: lo, ctxt } }
+    }
+
+    #[allow(deprecated)]
+    #[inline]
+    pub fn lo(self) -> BytePos {
+        self.lo
+    }
+    #[inline]
+    pub fn with_lo(self, lo: BytePos) -> Span {
+        Span::new(lo, self.hi(), self.ctxt())
+    }
+    #[allow(deprecated)]
+    #[inline]
+    pub fn hi(self) -> BytePos {
+        self.hi
+    }
+    #[inline]
+    pub fn with_hi(self, hi: BytePos) -> Span {
+        Span::new(self.lo(), hi, self.ctxt())
+    }
+    #[allow(deprecated)]
+    #[inline]
+    pub fn ctxt(self) -> SyntaxContext {
+        self.ctxt
+    }
+    #[inline]
+    pub fn with_ctxt(self, ctxt: SyntaxContext) -> Span {
+        Span::new(self.lo(), self.hi(), ctxt)
+    }
+
     /// Returns a new span representing just the end-point of this span
     pub fn end_point(self) -> Span {
-        let lo = cmp::max(self.hi.0 - 1, self.lo.0);
-        Span { lo: BytePos(lo), ..self }
+        let lo = cmp::max(self.hi().0 - 1, self.lo().0);
+        self.with_lo(BytePos(lo))
     }
 
     /// Returns a new span representing the next character after the end-point of this span
     pub fn next_point(self) -> Span {
-        let lo = cmp::max(self.hi.0, self.lo.0 + 1);
-        Span { lo: BytePos(lo), hi: BytePos(lo), ..self }
+        let lo = cmp::max(self.hi().0, self.lo().0 + 1);
+        Span::new(BytePos(lo), BytePos(lo), self.ctxt())
     }
 
     /// Returns `self` if `self` is not the dummy span, and `other` otherwise.
@@ -99,7 +143,7 @@ impl Span {
 
     /// Return true if `self` fully encloses `other`.
     pub fn contains(self, other: Span) -> bool {
-        self.lo <= other.lo && other.hi <= self.hi
+        self.lo() <= other.lo() && other.hi() <= self.hi()
     }
 
     /// Return true if the spans are equal with regards to the source text.
@@ -107,13 +151,13 @@ impl Span {
     /// Use this instead of `==` when either span could be generated code,
     /// and you only care that they point to the same bytes of source text.
     pub fn source_equal(&self, other: &Span) -> bool {
-        self.lo == other.lo && self.hi == other.hi
+        self.lo() == other.lo() && self.hi() == other.hi()
     }
 
     /// Returns `Some(span)`, where the start is trimmed by the end of `other`
     pub fn trim_start(self, other: Span) -> Option<Span> {
-        if self.hi > other.hi {
-            Some(Span { lo: cmp::max(self.lo, other.hi), .. self })
+        if self.hi() > other.hi() {
+            Some(self.with_lo(cmp::max(self.lo(), other.hi())))
         } else {
             None
         }
@@ -122,7 +166,7 @@ impl Span {
     /// Return the source span - this is either the supplied span, or the span for
     /// the macro callsite that expanded to it.
     pub fn source_callsite(self) -> Span {
-        self.ctxt.outer().expn_info().map(|info| info.call_site.source_callsite()).unwrap_or(self)
+        self.ctxt().outer().expn_info().map(|info| info.call_site.source_callsite()).unwrap_or(self)
     }
 
     /// Return the source callee.
@@ -132,19 +176,19 @@ impl Span {
     /// corresponding to the source callsite.
     pub fn source_callee(self) -> Option<NameAndSpan> {
         fn source_callee(info: ExpnInfo) -> NameAndSpan {
-            match info.call_site.ctxt.outer().expn_info() {
+            match info.call_site.ctxt().outer().expn_info() {
                 Some(info) => source_callee(info),
                 None => info.callee,
             }
         }
-        self.ctxt.outer().expn_info().map(source_callee)
+        self.ctxt().outer().expn_info().map(source_callee)
     }
 
     /// Check if a span is "internal" to a macro in which #[unstable]
     /// items can be used (that is, a macro marked with
     /// `#[allow_internal_unstable]`).
     pub fn allows_unstable(&self) -> bool {
-        match self.ctxt.outer().expn_info() {
+        match self.ctxt().outer().expn_info() {
             Some(info) => info.callee.allow_internal_unstable,
             None => false,
         }
@@ -152,7 +196,7 @@ impl Span {
 
     /// Check if this span arises from a compiler desugaring of kind `kind`.
     pub fn is_compiler_desugaring(&self, kind: CompilerDesugaringKind) -> bool {
-        match self.ctxt.outer().expn_info() {
+        match self.ctxt().outer().expn_info() {
             Some(info) => match info.callee.format {
                 ExpnFormat::CompilerDesugaring(k) => k == kind,
                 _ => false,
@@ -161,11 +205,23 @@ impl Span {
         }
     }
 
+    /// Return the compiler desugaring that created this span, or None
+    /// if this span is not from a desugaring.
+    pub fn compiler_desugaring_kind(&self) -> Option<CompilerDesugaringKind> {
+        match self.ctxt().outer().expn_info() {
+            Some(info) => match info.callee.format {
+                ExpnFormat::CompilerDesugaring(k) => Some(k),
+                _ => None
+            },
+            None => None
+        }
+    }
+
     /// Check if a span is "internal" to a macro in which `unsafe`
     /// can be used without triggering the `unsafe_code` lint
     //  (that is, a macro marked with `#[allow_internal_unsafe]`).
     pub fn allows_unsafe(&self) -> bool {
-        match self.ctxt.outer().expn_info() {
+        match self.ctxt().outer().expn_info() {
             Some(info) => info.callee.allow_internal_unsafe,
             None => false,
         }
@@ -175,7 +231,7 @@ impl Span {
         let mut prev_span = DUMMY_SP;
         let mut result = vec![];
         loop {
-            let info = match self.ctxt.outer().expn_info() {
+            let info = match self.ctxt().outer().expn_info() {
                 Some(info) => info,
                 None => break,
             };
@@ -205,42 +261,30 @@ impl Span {
 
     /// Return a `Span` that would enclose both `self` and `end`.
     pub fn to(self, end: Span) -> Span {
-        Span {
-            lo: cmp::min(self.lo, end.lo),
-            hi: cmp::max(self.hi, end.hi),
+        Span::new(
+            cmp::min(self.lo(), end.lo()),
+            cmp::max(self.hi(), end.hi()),
             // FIXME(jseyfried): self.ctxt should always equal end.ctxt here (c.f. issue #23480)
-            ctxt: if self.ctxt == SyntaxContext::empty() {
-                end.ctxt
-            } else {
-                self.ctxt
-            },
-        }
+            if self.ctxt() == SyntaxContext::empty() { end.ctxt() } else { self.ctxt() },
+        )
     }
 
     /// Return a `Span` between the end of `self` to the beginning of `end`.
     pub fn between(self, end: Span) -> Span {
-        Span {
-            lo: self.hi,
-            hi: end.lo,
-            ctxt: if end.ctxt == SyntaxContext::empty() {
-                end.ctxt
-            } else {
-                self.ctxt
-            }
-        }
+        Span::new(
+            self.hi(),
+            end.lo(),
+            if end.ctxt() == SyntaxContext::empty() { end.ctxt() } else { self.ctxt() },
+        )
     }
 
     /// Return a `Span` between the beginning of `self` to the beginning of `end`.
     pub fn until(self, end: Span) -> Span {
-        Span {
-            lo: self.lo,
-            hi: end.lo,
-            ctxt: if end.ctxt == SyntaxContext::empty() {
-                end.ctxt
-            } else {
-                self.ctxt
-            }
-        }
+        Span::new(
+            self.lo(),
+            end.lo(),
+            if end.ctxt() == SyntaxContext::empty() { end.ctxt() } else { self.ctxt() },
+        )
     }
 }
 
@@ -267,11 +311,11 @@ impl serialize::UseSpecializedEncodable for Span {
     fn default_encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
         s.emit_struct("Span", 2, |s| {
             s.emit_struct_field("lo", 0, |s| {
-                self.lo.encode(s)
+                self.lo().encode(s)
             })?;
 
             s.emit_struct_field("hi", 1, |s| {
-                self.hi.encode(s)
+                self.hi().encode(s)
             })
         })
     }
@@ -282,14 +326,14 @@ impl serialize::UseSpecializedDecodable for Span {
         d.read_struct("Span", 2, |d| {
             let lo = d.read_struct_field("lo", 0, Decodable::decode)?;
             let hi = d.read_struct_field("hi", 1, Decodable::decode)?;
-            Ok(Span { lo: lo, hi: hi, ctxt: NO_EXPANSION })
+            Ok(Span::new(lo, hi, NO_EXPANSION))
         })
     }
 }
 
 fn default_span_debug(span: Span, f: &mut fmt::Formatter) -> fmt::Result {
     write!(f, "Span {{ lo: {:?}, hi: {:?}, ctxt: {:?} }}",
-           span.lo, span.hi, span.ctxt)
+           span.lo(), span.hi(), span.ctxt())
 }
 
 impl fmt::Debug for Span {
@@ -298,8 +342,6 @@ impl fmt::Debug for Span {
     }
 }
 
-pub const DUMMY_SP: Span = Span { lo: BytePos(0), hi: BytePos(0), ctxt: NO_EXPANSION };
-
 impl MultiSpan {
     pub fn new() -> MultiSpan {
         MultiSpan {
diff --git a/src/libsyntax_pos/symbol.rs b/src/libsyntax_pos/symbol.rs
index e49f1f28e5f1d..4d3db15ef29db 100644
--- a/src/libsyntax_pos/symbol.rs
+++ b/src/libsyntax_pos/symbol.rs
@@ -115,6 +115,12 @@ impl Symbol {
     }
 }
 
+impl<'a> From<&'a str> for Symbol {
+    fn from(string: &'a str) -> Symbol {
+        Symbol::intern(string)
+    }
+}
+
 impl fmt::Debug for Symbol {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f, "{}({})", self, self.0)
diff --git a/src/stage0.txt b/src/stage0.txt
index e49b301abbf6b..892679c192916 100644
--- a/src/stage0.txt
+++ b/src/stage0.txt
@@ -12,7 +12,7 @@
 # source tarball for a stable release you'll likely see `1.x.0` for rustc and
 # `0.x.0` for Cargo where they were released on `date`.
 
-date: 2017-07-18
+date: 2017-08-29
 rustc: beta
 cargo: beta
 
diff --git a/src/test/codegen/dealloc-no-unwind.rs b/src/test/codegen/dealloc-no-unwind.rs
new file mode 100644
index 0000000000000..551b66e103a11
--- /dev/null
+++ b/src/test/codegen/dealloc-no-unwind.rs
@@ -0,0 +1,32 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+//
+// no-system-llvm
+// compile-flags: -O
+
+#![crate_type="lib"]
+
+struct A;
+
+impl Drop for A {
+    fn drop(&mut self) {
+        extern { fn foo(); }
+        unsafe { foo(); }
+    }
+}
+
+#[no_mangle]
+pub fn a(a: Box<i32>) {
+    // CHECK-LABEL: define void @a
+    // CHECK: call void @__rust_dealloc
+    // CHECK-NEXT: call void @foo
+    let _a = A;
+    drop(a);
+}
diff --git a/src/test/codegen/issue-34947-pow-i32.rs b/src/test/codegen/issue-34947-pow-i32.rs
new file mode 100644
index 0000000000000..0564cd2e5016c
--- /dev/null
+++ b/src/test/codegen/issue-34947-pow-i32.rs
@@ -0,0 +1,23 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// compile-flags: -O
+
+#![crate_type = "lib"]
+
+// CHECK-LABEL: @issue_34947
+#[no_mangle]
+pub fn issue_34947(x: i32) -> i32 {
+    // CHECK: mul
+    // CHECK-NEXT: mul
+    // CHECK-NEXT: mul
+    // CHECK-NEXT: ret
+    x.pow(5)
+}
diff --git a/src/test/compile-fail-fulldeps/gated-macro-reexports.rs b/src/test/compile-fail-fulldeps/gated-macro-reexports.rs
index 22c92623e1c19..2a20c28cfb871 100644
--- a/src/test/compile-fail-fulldeps/gated-macro-reexports.rs
+++ b/src/test/compile-fail-fulldeps/gated-macro-reexports.rs
@@ -16,6 +16,6 @@
 #![crate_type = "dylib"]
 
 #[macro_reexport(reexported)]
+//~^ ERROR macros reexports are experimental and possibly buggy
 #[macro_use] #[no_link]
 extern crate macro_reexport_1;
-//~^ ERROR macros reexports are experimental and possibly buggy
diff --git a/src/test/compile-fail/E0232.rs b/src/test/compile-fail/E0232.rs
index ce4f4638dac59..a33120bbebd23 100644
--- a/src/test/compile-fail/E0232.rs
+++ b/src/test/compile-fail/E0232.rs
@@ -12,7 +12,7 @@
 
 #[rustc_on_unimplemented]
 //~^ ERROR E0232
-//~| NOTE attribute requires a value
+//~| NOTE value required here
 //~| NOTE eg `#[rustc_on_unimplemented = "foo"]`
 trait Bar {}
 
diff --git a/src/test/compile-fail/check-static-values-constraints.rs b/src/test/compile-fail/check-static-values-constraints.rs
index 3642add32597b..c349aababd6c0 100644
--- a/src/test/compile-fail/check-static-values-constraints.rs
+++ b/src/test/compile-fail/check-static-values-constraints.rs
@@ -86,8 +86,9 @@ static STATIC8: SafeStruct = SafeStruct{field1: SafeEnum::Variant1,
 // This example should fail because field1 in the base struct is not safe
 static STATIC9: SafeStruct = SafeStruct{field1: SafeEnum::Variant1,
                                         ..SafeStruct{field1: SafeEnum::Variant3(WithDtor),
+//~^ ERROR destructors in statics are an unstable feature
+//~| ERROR statics are not allowed to have destructors
                                                      field2: SafeEnum::Variant1}};
-//~^^ ERROR destructors in statics are an unstable feature
 
 struct UnsafeStruct;
 
diff --git a/src/test/compile-fail/feature-gate-fn_must_use.rs b/src/test/compile-fail/feature-gate-fn_must_use.rs
index 2dd6b90407267..72fdcc76cf4f6 100644
--- a/src/test/compile-fail/feature-gate-fn_must_use.rs
+++ b/src/test/compile-fail/feature-gate-fn_must_use.rs
@@ -13,12 +13,12 @@
 struct MyStruct;
 
 impl MyStruct {
-    #[must_use]
-    fn need_to_use_method() -> bool { true } //~ WARN `#[must_use]` on methods is experimental
+    #[must_use] //~ WARN `#[must_use]` on methods is experimental
+    fn need_to_use_method() -> bool { true }
 }
 
-#[must_use]
-fn need_to_use_it() -> bool { true } //~ WARN `#[must_use]` on functions is experimental
+#[must_use] //~ WARN `#[must_use]` on functions is experimental
+fn need_to_use_it() -> bool { true }
 
 
 // Feature gates are tidy-required to have a specially named (or
diff --git a/src/test/compile-fail/feature-gate-generators.rs b/src/test/compile-fail/feature-gate-generators.rs
new file mode 100644
index 0000000000000..3754f92d8cde2
--- /dev/null
+++ b/src/test/compile-fail/feature-gate-generators.rs
@@ -0,0 +1,13 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+fn main() {
+    yield true; //~ ERROR yield syntax is experimental
+}
diff --git a/src/test/compile-fail/feature-gate-match_beginning_vert.rs b/src/test/compile-fail/feature-gate-match_beginning_vert.rs
new file mode 100644
index 0000000000000..9085563c99d6d
--- /dev/null
+++ b/src/test/compile-fail/feature-gate-match_beginning_vert.rs
@@ -0,0 +1,36 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#[allow(dead_code)]
+enum Foo {
+    A,
+    B,
+    C,
+    D,
+    E,
+}
+use Foo::*;
+
+fn main() {
+    let x = Foo::A;
+    match x {
+        | A => println!("A"),
+        //~^ ERROR: Use of a '|' at the beginning of a match arm is experimental (see issue #44101)
+        | B | C => println!("BC!"),
+        //~^ ERROR: Use of a '|' at the beginning of a match arm is experimental (see issue #44101)
+        | _ => {},
+        //~^ ERROR: Use of a '|' at the beginning of a match arm is experimental (see issue #44101)
+    };
+    match x {
+        A | B | C => println!("ABC!"),
+        _ => {},
+    };
+}
+
diff --git a/src/test/compile-fail/feature-gate-repr-simd.rs b/src/test/compile-fail/feature-gate-repr-simd.rs
index fdafb2ad950c9..429cec7ec90d0 100644
--- a/src/test/compile-fail/feature-gate-repr-simd.rs
+++ b/src/test/compile-fail/feature-gate-repr-simd.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#[repr(simd)]
-struct Foo(u64, u64); //~ error: SIMD types are experimental
+#[repr(simd)] //~ error: SIMD types are experimental
+struct Foo(u64, u64);
 
 fn main() {}
diff --git a/src/test/compile-fail/feature-gate-repr_align.rs b/src/test/compile-fail/feature-gate-repr_align.rs
index 8e986e197f269..9591d367a2d19 100644
--- a/src/test/compile-fail/feature-gate-repr_align.rs
+++ b/src/test/compile-fail/feature-gate-repr_align.rs
@@ -9,7 +9,7 @@
 // except according to those terms.
 #![feature(attr_literals)]
 
-#[repr(align(64))]
-struct Foo(u64, u64); //~ error: the struct `#[repr(align(u16))]` attribute is experimental
+#[repr(align(64))] //~ error: the struct `#[repr(align(u16))]` attribute is experimental
+struct Foo(u64, u64);
 
 fn main() {}
diff --git a/src/test/compile-fail/feature-gate-simd.rs b/src/test/compile-fail/feature-gate-simd.rs
index 168e84aa128c0..025eaca553336 100644
--- a/src/test/compile-fail/feature-gate-simd.rs
+++ b/src/test/compile-fail/feature-gate-simd.rs
@@ -11,13 +11,12 @@
 
 // pretty-expanded FIXME #23616
 
-#[repr(simd)]
+#[repr(simd)] //~ ERROR SIMD types are experimental
 struct RGBA {
     r: f32,
     g: f32,
     b: f32,
     a: f32
 }
-//~^^^^^^ ERROR SIMD types are experimental and possibly buggy (see issue #27731)
 
 pub fn main() {}
diff --git a/src/test/compile-fail/feature-gate/issue-43106-gating-of-builtin-attrs.rs b/src/test/compile-fail/feature-gate/issue-43106-gating-of-builtin-attrs.rs
index 204190d64acc1..6eec1779a2d87 100644
--- a/src/test/compile-fail/feature-gate/issue-43106-gating-of-builtin-attrs.rs
+++ b/src/test/compile-fail/feature-gate/issue-43106-gating-of-builtin-attrs.rs
@@ -354,8 +354,7 @@ mod repr {
     #[repr = "3900"] fn f() { }
     //~^ WARN unused attribute
 
-    #[repr = "3900"] struct S;
-    //~^ WARN unused attribute
+    struct S;
 
     #[repr = "3900"] type T = S;
     //~^ WARN unused attribute
diff --git a/src/test/compile-fail/lint-ctypes.rs b/src/test/compile-fail/lint-ctypes.rs
index 608b1eb0872ad..1d9b179c05d85 100644
--- a/src/test/compile-fail/lint-ctypes.rs
+++ b/src/test/compile-fail/lint-ctypes.rs
@@ -9,7 +9,7 @@
 // except according to those terms.
 
 #![deny(improper_ctypes)]
-#![feature(libc)]
+#![feature(libc, i128_type)]
 
 extern crate libc;
 
@@ -39,6 +39,8 @@ extern {
     pub fn str_type(p: &str); //~ ERROR: found Rust type
     pub fn box_type(p: Box<u32>); //~ ERROR found struct without
     pub fn char_type(p: char); //~ ERROR found Rust type
+    pub fn i128_type(p: i128); //~ ERROR found Rust type
+    pub fn u128_type(p: u128); //~ ERROR found Rust type
     pub fn trait_type(p: &Clone); //~ ERROR found Rust trait type
     pub fn tuple_type(p: (i32, i32)); //~ ERROR found Rust tuple type
     pub fn tuple_type2(p: I32Pair); //~ ERROR found Rust tuple type
diff --git a/src/test/compile-fail/lint-impl-fn.rs b/src/test/compile-fail/lint-impl-fn.rs
index 608aec327b63a..54a720d75b5ad 100644
--- a/src/test/compile-fail/lint-impl-fn.rs
+++ b/src/test/compile-fail/lint-impl-fn.rs
@@ -36,3 +36,8 @@ mod foo {
 fn main() {
     while true {} //~ ERROR: infinite loops
 }
+
+#[deny(while_true)]
+fn bar() {
+    while cfg!(unix) {} // no error
+}
diff --git a/src/test/compile-fail/static-drop-scope.rs b/src/test/compile-fail/static-drop-scope.rs
new file mode 100644
index 0000000000000..e5f10b65ceed7
--- /dev/null
+++ b/src/test/compile-fail/static-drop-scope.rs
@@ -0,0 +1,26 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(drop_types_in_const)]
+
+struct WithDtor;
+
+impl Drop for WithDtor {
+    fn drop(&mut self) {}
+}
+
+static FOO: Option<&'static WithDtor> = Some(&WithDtor);
+//~^ ERROR statics are not allowed to have destructors
+//~| ERROR borrowed value does not live long enoug
+
+static BAR: i32 = (WithDtor, 0).1;
+//~^ ERROR statics are not allowed to have destructors
+
+fn main () {}
diff --git a/src/test/mir-opt/end_region_1.rs b/src/test/mir-opt/end_region_1.rs
index 55dac4440275f..54409d3543ebc 100644
--- a/src/test/mir-opt/end_region_1.rs
+++ b/src/test/mir-opt/end_region_1.rs
@@ -22,16 +22,16 @@ fn main() {
 // START rustc.node4.SimplifyCfg-qualify-consts.after.mir
 //     let mut _0: ();
 //     let _1: i32;
-//     let _2: &'6_1rce i32;
+//     let _2: &'10_1rs i32;
 //
 //     bb0: {
 //         StorageLive(_1);
 //         _1 = const 3i32;
 //         StorageLive(_2);
-//         _2 = &'6_1rce _1;
+//         _2 = &'10_1rs _1;
 //         _0 = ();
 //         StorageDead(_2);
-//         EndRegion('6_1rce);
+//         EndRegion('10_1rs);
 //         StorageDead(_1);
 //         return;
 //     }
diff --git a/src/test/mir-opt/end_region_2.rs b/src/test/mir-opt/end_region_2.rs
index a1386ec47a13b..b37bd4188d970 100644
--- a/src/test/mir-opt/end_region_2.rs
+++ b/src/test/mir-opt/end_region_2.rs
@@ -27,8 +27,8 @@ fn main() {
 // START rustc.node4.SimplifyCfg-qualify-consts.after.mir
 //     let mut _0: ();
 //     let _2: bool;
-//     let _3: &'7_1rce bool;
-//     let _7: &'7_3rce bool;
+//     let _3: &'23_1rs bool;
+//     let _7: &'23_3rs bool;
 //     let mut _4: ();
 //     let mut _5: bool;
 //     bb0: {
@@ -38,7 +38,7 @@ fn main() {
 //         StorageLive(_2);
 //         _2 = const true;
 //         StorageLive(_3);
-//         _3 = &'7_1rce _2;
+//         _3 = &'23_1rs _2;
 //         StorageLive(_5);
 //         _5 = _2;
 //         switchInt(_5) -> [0u8: bb3, otherwise: bb2];
@@ -47,19 +47,19 @@ fn main() {
 //         _0 = ();
 //         StorageDead(_5);
 //         StorageDead(_3);
-//         EndRegion('7_1rce);
+//         EndRegion('23_1rs);
 //         StorageDead(_2);
 //         return;
 //     }
 //     bb3: {
 //         StorageDead(_5);
 //         StorageLive(_7);
-//         _7 = &'7_3rce _2;
+//         _7 = &'23_3rs _2;
 //         _1 = ();
 //         StorageDead(_7);
-//         EndRegion('7_3rce);
+//         EndRegion('23_3rs);
 //         StorageDead(_3);
-//         EndRegion('7_1rce);
+//         EndRegion('23_1rs);
 //         StorageDead(_2);
 //         goto -> bb1;
 //     }
diff --git a/src/test/mir-opt/end_region_3.rs b/src/test/mir-opt/end_region_3.rs
index b3d2809e76ceb..be9fc579ab636 100644
--- a/src/test/mir-opt/end_region_3.rs
+++ b/src/test/mir-opt/end_region_3.rs
@@ -28,8 +28,8 @@ fn main() {
 // START rustc.node4.SimplifyCfg-qualify-consts.after.mir
 //     let mut _0: ();
 //     let mut _1: bool;
-//     let _3: &'9_1rce bool;
-//     let _7: &'9_3rce bool;
+//     let _3: &'26_1rs bool;
+//     let _7: &'26_3rs bool;
 //     let mut _2: ();
 //     let mut _4: ();
 //     let mut _5: bool;
@@ -41,7 +41,7 @@ fn main() {
 //     bb1: {
 //         _1 = const true;
 //         StorageLive(_3);
-//         _3 = &'9_1rce _1;
+//         _3 = &'26_1rs _1;
 //         StorageLive(_5);
 //         _5 = _1;
 //         switchInt(_5) -> [0u8: bb3, otherwise: bb2];
@@ -50,7 +50,7 @@ fn main() {
 //         _0 = ();
 //         StorageDead(_5);
 //         StorageDead(_3);
-//         EndRegion('9_1rce);
+//         EndRegion('26_1rs);
 //         StorageDead(_1);
 //         return;
 //     }
@@ -58,12 +58,12 @@ fn main() {
 //         _4 = ();
 //         StorageDead(_5);
 //         StorageLive(_7);
-//         _7 = &'9_3rce _1;
+//         _7 = &'26_3rs _1;
 //         _2 = ();
 //         StorageDead(_7);
-//         EndRegion('9_3rce);
+//         EndRegion('26_3rs);
 //         StorageDead(_3);
-//         EndRegion('9_1rce);
+//         EndRegion('26_1rs);
 //         goto -> bb1;
 //     }
 // END rustc.node4.SimplifyCfg-qualify-consts.after.mir
diff --git a/src/test/mir-opt/end_region_4.rs b/src/test/mir-opt/end_region_4.rs
index 0b34231b4eec6..58ce1ed5b84b7 100644
--- a/src/test/mir-opt/end_region_4.rs
+++ b/src/test/mir-opt/end_region_4.rs
@@ -33,8 +33,8 @@ fn foo(i: i32) {
 //     let mut _0: ();
 //     let _1: D;
 //     let _2: i32;
-//     let _3: &'6_2rce i32;
-//     let _6: &'6_4rce i32;
+//     let _3: &'26_2rs i32;
+//     let _6: &'26_4rs i32;
 //     let mut _4: ();
 //     let mut _5: i32;
 //     bb0: {
@@ -43,7 +43,7 @@ fn foo(i: i32) {
 //         StorageLive(_2);
 //         _2 = const 0i32;
 //         StorageLive(_3);
-//         _3 = &'6_2rce _2;
+//         _3 = &'26_2rs _2;
 //         StorageLive(_5);
 //         _5 = (*_3);
 //         _4 = const foo(_5) -> [return: bb1, unwind: bb3];
@@ -51,12 +51,12 @@ fn foo(i: i32) {
 //     bb1: {
 //         StorageDead(_5);
 //         StorageLive(_6);
-//         _6 = &'6_4rce _2;
+//         _6 = &'26_4rs _2;
 //         _0 = ();
 //         StorageDead(_6);
-//         EndRegion('6_4rce);
+//         EndRegion('26_4rs);
 //         StorageDead(_3);
-//         EndRegion('6_2rce);
+//         EndRegion('26_2rs);
 //         StorageDead(_2);
 //         drop(_1) -> bb4;
 //     }
@@ -64,7 +64,7 @@ fn foo(i: i32) {
 //         resume;
 //     }
 //     bb3: {
-//         EndRegion('6_2rce);
+//         EndRegion('26_2rs);
 //         drop(_1) -> bb2;
 //     }
 //     bb4: {
diff --git a/src/test/mir-opt/end_region_5.rs b/src/test/mir-opt/end_region_5.rs
index e51bb9350db60..be62a5473a6ff 100644
--- a/src/test/mir-opt/end_region_5.rs
+++ b/src/test/mir-opt/end_region_5.rs
@@ -31,21 +31,21 @@ fn foo<F>(f: F) where F: FnOnce() -> i32 {
 //     let mut _0: ();
 //     let _1: D;
 //     let mut _2: ();
-//     let mut _3: [closure@NodeId(18) d:&'19mce D];
-//     let mut _4: &'19mce D;
+//     let mut _3: [closure@NodeId(18) d:&'14s D];
+//     let mut _4: &'14s D;
 //     bb0: {
 //         StorageLive(_1);
 //         _1 = D::{{constructor}}(const 0i32,);
 //         StorageLive(_3);
 //         StorageLive(_4);
-//         _4 = &'19mce _1;
+//         _4 = &'14s _1;
 //         _3 = [closure@NodeId(18)] { d: _4 };
 //         StorageDead(_4);
 //         _2 = const foo(_3) -> [return: bb1, unwind: bb3];
 //     }
 //     bb1: {
 //         StorageDead(_3);
-//         EndRegion('19mce);
+//         EndRegion('14s);
 //         _0 = ();
 //         drop(_1) -> bb4;
 //     }
@@ -53,7 +53,7 @@ fn foo<F>(f: F) where F: FnOnce() -> i32 {
 //         resume;
 //     }
 //     bb3: {
-//         EndRegion('19mce);
+//         EndRegion('14s);
 //         drop(_1) -> bb2;
 //     }
 //     bb4: {
@@ -64,13 +64,13 @@ fn foo<F>(f: F) where F: FnOnce() -> i32 {
 // END rustc.node4.SimplifyCfg-qualify-consts.after.mir
 
 // START rustc.node18.SimplifyCfg-qualify-consts.after.mir
-// fn main::{{closure}}(_1: [closure@NodeId(18) d:&'19mce D]) -> i32 {
+// fn main::{{closure}}(_1: [closure@NodeId(18) d:&'14s D]) -> i32 {
 //    let mut _0: i32;
 //    let mut _2: i32;
 //
 //    bb0: {
 //        StorageLive(_2);
-//        _2 = ((*(_1.0: &'19mce D)).0: i32);
+//        _2 = ((*(_1.0: &'14s D)).0: i32);
 //        _0 = _2;
 //        StorageDead(_2);
 //        return;
diff --git a/src/test/mir-opt/end_region_6.rs b/src/test/mir-opt/end_region_6.rs
index c55e6d105cbdc..23b92583a11da 100644
--- a/src/test/mir-opt/end_region_6.rs
+++ b/src/test/mir-opt/end_region_6.rs
@@ -31,21 +31,21 @@ fn foo<F>(f: F) where F: FnOnce() -> i32 {
 //     let mut _0: ();
 //     let _1: D;
 //     let mut _2: ();
-//     let mut _3: [closure@NodeId(22) d:&'23mce D];
-//     let mut _4: &'23mce D;
+//     let mut _3: [closure@NodeId(22) d:&'19s D];
+//     let mut _4: &'19s D;
 //     bb0: {
 //         StorageLive(_1);
 //         _1 = D::{{constructor}}(const 0i32,);
 //         StorageLive(_3);
 //         StorageLive(_4);
-//         _4 = &'23mce _1;
+//         _4 = &'19s _1;
 //         _3 = [closure@NodeId(22)] { d: _4 };
 //         StorageDead(_4);
 //         _2 = const foo(_3) -> [return: bb1, unwind: bb3];
 //     }
 //     bb1: {
 //         StorageDead(_3);
-//         EndRegion('23mce);
+//         EndRegion('19s);
 //         _0 = ();
 //         drop(_1) -> bb4;
 //     }
@@ -53,7 +53,7 @@ fn foo<F>(f: F) where F: FnOnce() -> i32 {
 //         resume;
 //     }
 //     bb3: {
-//         EndRegion('23mce);
+//         EndRegion('19s);
 //         drop(_1) -> bb2;
 //     }
 //     bb4: {
@@ -63,20 +63,20 @@ fn foo<F>(f: F) where F: FnOnce() -> i32 {
 // END rustc.node4.SimplifyCfg-qualify-consts.after.mir
 
 // START rustc.node22.SimplifyCfg-qualify-consts.after.mir
-// fn main::{{closure}}(_1: [closure@NodeId(22) d:&'23mce D]) -> i32 {
+// fn main::{{closure}}(_1: [closure@NodeId(22) d:&'19s D]) -> i32 {
 //     let mut _0: i32;
-//     let _2: &'14_0rce D;
+//     let _2: &'15_0rs D;
 //     let mut _3: i32;
 //
 //     bb0: {
 //         StorageLive(_2);
-//         _2 = &'14_0rce (*(_1.0: &'23mce D));
+//         _2 = &'15_0rs (*(_1.0: &'19s D));
 //         StorageLive(_3);
 //         _3 = ((*_2).0: i32);
 //         _0 = _3;
 //         StorageDead(_3);
 //         StorageDead(_2);
-//         EndRegion('14_0rce);
+//         EndRegion('15_0rs);
 //         return;
 //     }
 // END rustc.node22.SimplifyCfg-qualify-consts.after.mir
diff --git a/src/test/mir-opt/end_region_7.rs b/src/test/mir-opt/end_region_7.rs
index 9c8e3ec08d498..ee0615f2bb312 100644
--- a/src/test/mir-opt/end_region_7.rs
+++ b/src/test/mir-opt/end_region_7.rs
@@ -74,18 +74,18 @@ fn foo<F>(f: F) where F: FnOnce() -> i32 {
 // START rustc.node22.SimplifyCfg-qualify-consts.after.mir
 // fn main::{{closure}}(_1: [closure@NodeId(22) d:D]) -> i32 {
 //     let mut _0: i32;
-//     let _2: &'14_0rce D;
+//     let _2: &'15_0rs D;
 //     let mut _3: i32;
 //
 //     bb0: {
 //         StorageLive(_2);
-//         _2 = &'14_0rce (_1.0: D);
+//         _2 = &'15_0rs (_1.0: D);
 //         StorageLive(_3);
 //         _3 = ((*_2).0: i32);
 //         _0 = _3;
 //         StorageDead(_3);
 //         StorageDead(_2);
-//         EndRegion('14_0rce);
+//         EndRegion('15_0rs);
 //         drop(_1) -> bb1;
 //     }
 //     bb1: {
diff --git a/src/test/mir-opt/end_region_8.rs b/src/test/mir-opt/end_region_8.rs
index b4dbec5cd2dd7..ef184e39c0061 100644
--- a/src/test/mir-opt/end_region_8.rs
+++ b/src/test/mir-opt/end_region_8.rs
@@ -31,15 +31,15 @@ fn foo<F>(f: F) where F: FnOnce() -> i32 {
 // fn main() -> () {
 //    let mut _0: ();
 //    let _1: D;
-//    let _2: &'6_1rce D;
+//    let _2: &'21_1rs D;
 //    let mut _3: ();
-//    let mut _4: [closure@NodeId(22) r:&'6_1rce D];
-//    let mut _5: &'6_1rce D;
+//    let mut _4: [closure@NodeId(22) r:&'21_1rs D];
+//    let mut _5: &'21_1rs D;
 //    bb0: {
 //        StorageLive(_1);
 //        _1 = D::{{constructor}}(const 0i32,);
 //        StorageLive(_2);
-//        _2 = &'6_1rce _1;
+//        _2 = &'21_1rs _1;
 //        StorageLive(_4);
 //        StorageLive(_5);
 //        _5 = _2;
@@ -51,14 +51,14 @@ fn foo<F>(f: F) where F: FnOnce() -> i32 {
 //        StorageDead(_4);
 //        _0 = ();
 //        StorageDead(_2);
-//        EndRegion('6_1rce);
+//        EndRegion('21_1rs);
 //        drop(_1) -> bb4;
 //    }
 //    bb2: {
 //        resume;
 //    }
 //    bb3: {
-//        EndRegion('6_1rce);
+//        EndRegion('21_1rs);
 //        drop(_1) -> bb2;
 //    }
 //    bb4: {
@@ -69,13 +69,13 @@ fn foo<F>(f: F) where F: FnOnce() -> i32 {
 // END rustc.node4.SimplifyCfg-qualify-consts.after.mir
 
 // START rustc.node22.SimplifyCfg-qualify-consts.after.mir
-// fn main::{{closure}}(_1: [closure@NodeId(22) r:&'6_1rce D]) -> i32 {
+// fn main::{{closure}}(_1: [closure@NodeId(22) r:&'21_1rs D]) -> i32 {
 //     let mut _0: i32;
 //     let mut _2: i32;
 //
 //     bb0: {
 //         StorageLive(_2);
-//         _2 = ((*(_1.0: &'6_1rce D)).0: i32);
+//         _2 = ((*(_1.0: &'21_1rs D)).0: i32);
 //         _0 = _2;
 //         StorageDead(_2);
 //         return;
diff --git a/src/test/mir-opt/end_region_9.rs b/src/test/mir-opt/end_region_9.rs
index deff984e4d0de..719bc3ff9dd04 100644
--- a/src/test/mir-opt/end_region_9.rs
+++ b/src/test/mir-opt/end_region_9.rs
@@ -42,7 +42,7 @@ fn main() {
 //     let mut _0: ();
 //     let mut _1: bool;
 //     let _2: i32;
-//     let mut _4: &'13_0rce i32;
+//     let mut _4: &'13_0rs i32;
 //     let mut _3: ();
 //     let mut _5: !;
 //     let mut _6: ();
@@ -68,14 +68,14 @@ fn main() {
 //        _0 = ();
 //        StorageDead(_7);
 //        StorageDead(_4);
-//        EndRegion('13_0rce);
+//        EndRegion('13_0rs);
 //        StorageDead(_2);
 //        StorageDead(_1);
 //        return;
 //    }
 //
 //    bb3: {
-//        _4 = &'13_0rce _2;
+//        _4 = &'13_0rs _2;
 //        _6 = ();
 //        StorageDead(_7);
 //        _1 = const true;
diff --git a/src/test/mir-opt/issue-43457.rs b/src/test/mir-opt/issue-43457.rs
index 708784df317a6..2a36672a45774 100644
--- a/src/test/mir-opt/issue-43457.rs
+++ b/src/test/mir-opt/issue-43457.rs
@@ -30,14 +30,14 @@ fn main() { }
 //     scope 1 {
 //         let _2: std::cell::RefCell<i32>;
 //     }
-//     let mut _3: std::cell::RefMut<'17dce, i32>;
-//     let mut _4: &'17dce std::cell::RefCell<i32>;
+//     let mut _3: std::cell::RefMut<'17ds, i32>;
+//     let mut _4: &'17ds std::cell::RefCell<i32>;
 //
 //     bb0: {
 //         StorageLive(_2);
 //         _2 = _1;
 //         StorageLive(_4);
-//         _4 = &'17dce _2;
+//         _4 = &'17ds _2;
 //         _3 = const <std::cell::RefCell<T>>::borrow_mut(_4) -> bb1;
 //     }
 //
@@ -47,7 +47,7 @@ fn main() { }
 //
 //     bb2: {
 //         StorageDead(_4);
-//         EndRegion('17dce);
+//         EndRegion('17ds);
 //         _0 = ();
 //         StorageDead(_2);
 //         return;
diff --git a/src/test/mir-opt/validate_1.rs b/src/test/mir-opt/validate_1.rs
index 677c92ea71b7a..ae9dcf8b7352d 100644
--- a/src/test/mir-opt/validate_1.rs
+++ b/src/test/mir-opt/validate_1.rs
@@ -37,19 +37,19 @@ fn main() {
 // START rustc.node23.EraseRegions.after.mir
 // fn main() -> () {
 //     bb0: {
-//         Validate(Suspend(ReScope(Misc(NodeId(34)))), [_1: i32]);
+//         Validate(Suspend(ReScope(Node(ItemLocalId(10)))), [_1: i32]);
 //         _6 = &ReErased mut _1;
-//         Validate(Acquire, [(*_6): i32/ReScope(Misc(NodeId(34)))]);
-//         Validate(Suspend(ReScope(Misc(NodeId(34)))), [(*_6): i32/ReScope(Misc(NodeId(34)))]);
+//         Validate(Acquire, [(*_6): i32/ReScope(Node(ItemLocalId(10)))]);
+//         Validate(Suspend(ReScope(Node(ItemLocalId(10)))), [(*_6): i32/ReScope(Node(ItemLocalId(10)))]);
 //         _5 = &ReErased mut (*_6);
-//         Validate(Acquire, [(*_5): i32/ReScope(Misc(NodeId(34)))]);
-//         Validate(Release, [_2: (), _3: &ReScope(Misc(NodeId(34))) Test, _5: &ReScope(Misc(NodeId(34))) mut i32]);
+//         Validate(Acquire, [(*_5): i32/ReScope(Node(ItemLocalId(10)))]);
+//         Validate(Release, [_2: (), _3: &ReScope(Node(ItemLocalId(10))) Test, _5: &ReScope(Node(ItemLocalId(10))) mut i32]);
 //         _2 = const Test::foo(_3, _5) -> bb1;
 //     }
 //
 //     bb1: {
 //         Validate(Acquire, [_2: ()]);
-//         EndRegion(ReScope(Misc(NodeId(34))));
+//         EndRegion(ReScope(Node(ItemLocalId(10))));
 //         return;
 //     }
 // }
@@ -61,15 +61,15 @@ fn main() {
 //         StorageLive(_3);
 //         _3 = _2;
 //         StorageLive(_4);
-//         Validate(Suspend(ReScope(Remainder(BlockRemainder { block: NodeId(41), first_statement_index: 0 }))), [(*_3): i32]);
+//         Validate(Suspend(ReScope(Remainder(BlockRemainder { block: ItemLocalId(22), first_statement_index: 0 }))), [(*_3): i32]);
 //         _4 = &ReErased (*_3);
-//         Validate(Acquire, [(*_4): i32/ReScope(Remainder(BlockRemainder { block: NodeId(41), first_statement_index: 0 })) (imm)]);
+//         Validate(Acquire, [(*_4): i32/ReScope(Remainder(BlockRemainder { block: ItemLocalId(22), first_statement_index: 0 })) (imm)]);
 //         StorageLive(_5);
 //         _5 = (*_4);
 //         _0 = _5;
 //         StorageDead(_5);
 //         StorageDead(_4);
-//         EndRegion(ReScope(Remainder(BlockRemainder { block: NodeId(41), first_statement_index: 0 })));
+//         EndRegion(ReScope(Remainder(BlockRemainder { block: ItemLocalId(22), first_statement_index: 0 })));
 //         StorageDead(_3);
 //         return;
 //     }
diff --git a/src/test/mir-opt/validate_3.rs b/src/test/mir-opt/validate_3.rs
index 9140cf5768f59..116e35b2d6f26 100644
--- a/src/test/mir-opt/validate_3.rs
+++ b/src/test/mir-opt/validate_3.rs
@@ -32,18 +32,18 @@ fn main() {
 // fn main() -> () {
 //     let mut _5: &ReErased i32;
 //     bb0: {
-//         Validate(Suspend(ReScope(Misc(NodeId(46)))), [((*_2).0: i32): i32/ReScope(Remainder(BlockRemainder { block: NodeId(18), first_statement_index: 3 })) (imm)]);
+//         Validate(Suspend(ReScope(Node(ItemLocalId(17)))), [((*_2).0: i32): i32/ReScope(Remainder(BlockRemainder { block: ItemLocalId(19), first_statement_index: 3 })) (imm)]);
 //         _5 = &ReErased ((*_2).0: i32);
-//         Validate(Acquire, [(*_5): i32/ReScope(Misc(NodeId(46))) (imm)]);
-//         Validate(Suspend(ReScope(Misc(NodeId(46)))), [(*_5): i32/ReScope(Misc(NodeId(46))) (imm)]);
+//         Validate(Acquire, [(*_5): i32/ReScope(Node(ItemLocalId(17))) (imm)]);
+//         Validate(Suspend(ReScope(Node(ItemLocalId(17)))), [(*_5): i32/ReScope(Node(ItemLocalId(17))) (imm)]);
 //         _4 = &ReErased (*_5);
-//         Validate(Acquire, [(*_4): i32/ReScope(Misc(NodeId(46))) (imm)]);
-//         Validate(Release, [_3: (), _4: &ReScope(Misc(NodeId(46))) i32]);
+//         Validate(Acquire, [(*_4): i32/ReScope(Node(ItemLocalId(17))) (imm)]);
+//         Validate(Release, [_3: (), _4: &ReScope(Node(ItemLocalId(17))) i32]);
 //         _3 = const foo(_4) -> bb1;
 //     }
 //     bb1: {
-//         EndRegion(ReScope(Misc(NodeId(46))));
-//         EndRegion(ReScope(Remainder(BlockRemainder { block: NodeId(18), first_statement_index: 3 })));
+//         EndRegion(ReScope(Node(ItemLocalId(17))));
+//         EndRegion(ReScope(Remainder(BlockRemainder { block: ItemLocalId(19), first_statement_index: 3 })));
 //         return;
 //     }
 // }
diff --git a/src/test/mir-opt/validate_5.rs b/src/test/mir-opt/validate_5.rs
index 0182e6e296445..ef2073dcc4b0f 100644
--- a/src/test/mir-opt/validate_5.rs
+++ b/src/test/mir-opt/validate_5.rs
@@ -50,12 +50,12 @@ fn main() {
 //         _3 = _2;
 //         StorageLive(_4);
 //         StorageLive(_5);
-//         Validate(Suspend(ReScope(Misc(NodeId(44)))), [(*_3): i32]);
+//         Validate(Suspend(ReScope(Node(ItemLocalId(9)))), [(*_3): i32]);
 //         _5 = &ReErased mut (*_3);
-//         Validate(Acquire, [(*_5): i32/ReScope(Misc(NodeId(44)))]);
+//         Validate(Acquire, [(*_5): i32/ReScope(Node(ItemLocalId(9)))]);
 //         _4 = _5 as *mut i32 (Misc);
 //         StorageDead(_5);
-//         EndRegion(ReScope(Misc(NodeId(44))));
+//         EndRegion(ReScope(Node(ItemLocalId(9))));
 //         Validate(Release, [_0: bool, _4: *mut i32]);
 //         _0 = const write_42(_4) -> bb1;
 //     }
diff --git a/src/test/parse-fail/struct-literal-restrictions-in-lamda.rs b/src/test/parse-fail/struct-literal-restrictions-in-lamda.rs
new file mode 100644
index 0000000000000..6b7a26556f430
--- /dev/null
+++ b/src/test/parse-fail/struct-literal-restrictions-in-lamda.rs
@@ -0,0 +1,29 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// compile-flags: -Z parse-only
+
+struct Foo {
+    x: isize,
+}
+
+impl Foo {
+    fn hi(&self) -> bool {
+        true
+    }
+}
+
+fn main() {
+    while || Foo {
+        x: 3    //~ ERROR expected type, found `3`
+    }.hi() { //~ ERROR expected one of `.`, `;`, `?`, `}`, or an operator, found `{`
+        println!("yo");
+    }
+}
diff --git a/src/test/run-make/extern-fn-struct-passing-abi/test.c b/src/test/run-make/extern-fn-struct-passing-abi/test.c
index 44a940a17a98a..25cd6da10b8fd 100644
--- a/src/test/run-make/extern-fn-struct-passing-abi/test.c
+++ b/src/test/run-make/extern-fn-struct-passing-abi/test.c
@@ -43,6 +43,16 @@ struct FloatPoint {
     double y;
 };
 
+struct FloatOne {
+    double x;
+};
+
+struct IntOdd {
+    int8_t a;
+    int8_t b;
+    int8_t c;
+};
+
 // System V x86_64 ABI:
 // a, b, c, d, e should be in registers
 // s should be byval pointer
@@ -283,7 +293,7 @@ struct Huge huge_struct(struct Huge s) {
 // p should be in registers
 // return should be in registers
 //
-// Win64 ABI:
+// Win64 ABI and 64-bit PowerPC ELFv1 ABI:
 // p should be a byval pointer
 // return should be in a hidden sret pointer
 struct FloatPoint float_point(struct FloatPoint p) {
@@ -292,3 +302,23 @@ struct FloatPoint float_point(struct FloatPoint p) {
 
     return p;
 }
+
+// 64-bit PowerPC ELFv1 ABI:
+// f1 should be in a register
+// return should be in a hidden sret pointer
+struct FloatOne float_one(struct FloatOne f1) {
+    assert(f1.x == 7.);
+
+    return f1;
+}
+
+// 64-bit PowerPC ELFv1 ABI:
+// i should be in the least-significant bits of a register
+// return should be in a hidden sret pointer
+struct IntOdd int_odd(struct IntOdd i) {
+    assert(i.a == 1);
+    assert(i.b == 2);
+    assert(i.c == 3);
+
+    return i;
+}
diff --git a/src/test/run-make/extern-fn-struct-passing-abi/test.rs b/src/test/run-make/extern-fn-struct-passing-abi/test.rs
index aaae7ae4fb49b..54a4f868eb4e5 100644
--- a/src/test/run-make/extern-fn-struct-passing-abi/test.rs
+++ b/src/test/run-make/extern-fn-struct-passing-abi/test.rs
@@ -53,6 +53,20 @@ struct FloatPoint {
     y: f64
 }
 
+#[derive(Clone, Copy, Debug, PartialEq)]
+#[repr(C)]
+struct FloatOne {
+    x: f64,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq)]
+#[repr(C)]
+struct IntOdd {
+    a: i8,
+    b: i8,
+    c: i8,
+}
+
 #[link(name = "test", kind = "static")]
 extern {
     fn byval_rect(a: i32, b: i32, c: i32, d: i32, e: i32, s: Rect);
@@ -83,6 +97,10 @@ extern {
     fn huge_struct(s: Huge) -> Huge;
 
     fn float_point(p: FloatPoint) -> FloatPoint;
+
+    fn float_one(f: FloatOne) -> FloatOne;
+
+    fn int_odd(i: IntOdd) -> IntOdd;
 }
 
 fn main() {
@@ -91,6 +109,8 @@ fn main() {
     let u = FloatRect { a: 3489, b: 3490, c: 8. };
     let v = Huge { a: 5647, b: 5648, c: 5649, d: 5650, e: 5651 };
     let p = FloatPoint { x: 5., y: -3. };
+    let f1 = FloatOne { x: 7. };
+    let i = IntOdd { a: 1, b: 2, c: 3 };
 
     unsafe {
         byval_rect(1, 2, 3, 4, 5, s);
@@ -113,5 +133,12 @@ fn main() {
         assert_eq!(sret_byval_struct(1, 2, 3, 4, s), t);
         assert_eq!(sret_split_struct(1, 2, s), t);
         assert_eq!(float_point(p), p);
+        assert_eq!(int_odd(i), i);
+
+        // MSVC/GCC/Clang are not consistent in the ABI of single-float aggregates.
+        // x86_64: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82028
+        // i686: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82041
+        #[cfg(not(all(windows, target_env = "gnu")))]
+        assert_eq!(float_one(f1), f1);
     }
 }
diff --git a/src/test/run-make/extern-fn-with-packed-struct/test.c b/src/test/run-make/extern-fn-with-packed-struct/test.c
index 506954fca4617..4124e202c1dd0 100644
--- a/src/test/run-make/extern-fn-with-packed-struct/test.c
+++ b/src/test/run-make/extern-fn-with-packed-struct/test.c
@@ -1,6 +1,8 @@
 // ignore-license
 // Pragma needed cause of gcc bug on windows: http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52991
 
+#include <assert.h>
+
 #ifdef _MSC_VER
 #pragma pack(push,1)
 struct Foo {
@@ -18,5 +20,8 @@ struct __attribute__((packed)) Foo {
 #endif
 
 struct Foo foo(struct Foo foo) {
+    assert(foo.a == 1);
+    assert(foo.b == 2);
+    assert(foo.c == 3);
     return foo;
 }
diff --git a/src/test/run-make/extern-fn-with-packed-struct/test.rs b/src/test/run-make/extern-fn-with-packed-struct/test.rs
index 9e81636e36703..d2540ad61542b 100644
--- a/src/test/run-make/extern-fn-with-packed-struct/test.rs
+++ b/src/test/run-make/extern-fn-with-packed-struct/test.rs
@@ -8,36 +8,14 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use std::fmt;
-
-#[repr(packed)]
-#[derive(Copy, Clone)]
+#[repr(C, packed)]
+#[derive(Copy, Clone, Debug, PartialEq)]
 struct Foo {
     a: i8,
     b: i16,
     c: i8
 }
 
-impl PartialEq for Foo {
-    fn eq(&self, other: &Foo) -> bool {
-        self.a == other.a && self.b == other.b && self.c == other.c
-    }
-}
-
-impl fmt::Debug for Foo {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        let a = self.a;
-        let b = self.b;
-        let c = self.c;
-
-        f.debug_struct("Foo")
-            .field("a", &a)
-            .field("b", &b)
-            .field("c", &c)
-            .finish()
-    }
-}
-
 #[link(name = "test", kind = "static")]
 extern {
     fn foo(f: Foo) -> Foo;
diff --git a/src/test/run-make/sysroot-crates-are-unstable/Makefile b/src/test/run-make/sysroot-crates-are-unstable/Makefile
index 4b7052f9b9493..a35174b3c2ac4 100644
--- a/src/test/run-make/sysroot-crates-are-unstable/Makefile
+++ b/src/test/run-make/sysroot-crates-are-unstable/Makefile
@@ -1,35 +1,2 @@
--include ../tools.mk
-
-# This is a whitelist of files which are stable crates or simply are not crates,
-# we don't check for the instability of these crates as they're all stable!
-STABLE_CRATES := \
-	std \
-	core \
-	proc_macro \
-	rsbegin.o \
-	rsend.o \
-	dllcrt2.o \
-	crt2.o \
-	clang_rt.%_dynamic.dylib
-
-# Generate a list of all crates in the sysroot. To do this we list all files in
-# rustc's sysroot, look at the filename, strip everything after the `-`, and
-# strip the leading `lib` (if present)
-SYSROOT := $(shell $(RUSTC) --print sysroot)
-LIBS := $(wildcard $(SYSROOT)/lib/rustlib/$(TARGET)/lib/*)
-LIBS := $(foreach lib,$(LIBS),$(notdir $(lib)))
-LIBS := $(foreach lib,$(LIBS),$(word 1,$(subst -, ,$(lib))))
-LIBS := $(foreach lib,$(LIBS),$(patsubst lib%,%,$(lib)))
-LIBS := $(filter-out $(STABLE_CRATES),$(LIBS))
-
-all: $(foreach lib,$(LIBS),check-crate-$(lib)-is-unstable)
-
-check-crate-%-is-unstable:
-	@echo verifying $* is an unstable crate
-	@echo 'extern crate $*;' | \
-		$(RUSTC) - --crate-type rlib 2>&1 | cat > $(TMPDIR)/$*; \
-		true
-	@grep -q 'use of unstable library feature' $(TMPDIR)/$* || \
-		(echo crate $* is not unstable && \
-		cat $(TMPDIR)/$* && \
-		false)
+all:
+	python2.7 test.py
diff --git a/src/test/run-make/sysroot-crates-are-unstable/test.py b/src/test/run-make/sysroot-crates-are-unstable/test.py
new file mode 100644
index 0000000000000..210059e1010df
--- /dev/null
+++ b/src/test/run-make/sysroot-crates-are-unstable/test.py
@@ -0,0 +1,71 @@
+# Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+# file at the top-level directory of this distribution and at
+# http://rust-lang.org/COPYRIGHT.
+#
+# Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+# http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+# <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+# option. This file may not be copied, modified, or distributed
+# except according to those terms.
+
+import sys
+import os
+from os import listdir
+from os.path import isfile, join
+from subprocess import PIPE, Popen
+
+
+# This is a whitelist of files which are stable crates or simply are not crates,
+# we don't check for the instability of these crates as they're all stable!
+STABLE_CRATES = ['std', 'core', 'proc_macro', 'rsbegin.o', 'rsend.o', 'dllcrt2.o', 'crt2.o',
+                 'clang_rt']
+
+
+def convert_to_string(s):
+    if s.__class__.__name__ == 'bytes':
+        return s.decode('utf-8')
+    return s
+
+
+def exec_command(command, to_input=None):
+    child = None
+    if to_input is None:
+        child = Popen(command, stdout=PIPE, stderr=PIPE)
+    else:
+        child = Popen(command, stdout=PIPE, stderr=PIPE, stdin=PIPE)
+    stdout, stderr = child.communicate(input=to_input)
+    return (convert_to_string(stdout), convert_to_string(stderr))
+
+
+def check_lib(lib):
+    if lib['name'] in STABLE_CRATES:
+        return True
+    print('verifying if {} is an unstable crate'.format(lib['name']))
+    stdout, stderr = exec_command([os.environ['RUSTC'], '-', '--crate-type', 'rlib',
+                                   '--extern', '{}={}'.format(lib['name'], lib['path'])],
+                                  to_input='extern crate {};'.format(lib['name']))
+    if not 'use of unstable library feature' in '{}{}'.format(stdout, stderr):
+        print('crate {} "{}" is not unstable'.format(lib['name'], lib['path']))
+        print('{}{}'.format(stdout, stderr))
+        print('')
+        return False
+    return True
+
+# Generate a list of all crates in the sysroot. To do this we list all files in
+# rustc's sysroot, look at the filename, strip everything after the `-`, and
+# strip the leading `lib` (if present)
+def get_all_libs(dir_path):
+    return [{ 'path': join(dir_path, f), 'name': f[3:].split('-')[0] }
+            for f in listdir(dir_path)
+            if isfile(join(dir_path, f)) and f.endswith('.rlib') and f not in STABLE_CRATES]
+
+
+sysroot = exec_command([os.environ['RUSTC'], '--print', 'sysroot'])[0].replace('\n', '')
+libs = get_all_libs(join(sysroot, 'lib/rustlib/{}/lib'.format(os.environ['TARGET'])))
+
+ret = 0
+for lib in libs:
+    if not check_lib(lib):
+        # We continue so users can see all the not unstable crates.
+        ret = 1
+sys.exit(ret)
diff --git a/src/test/run-pass-fulldeps/proc-macro/attr-on-trait.rs b/src/test/run-pass-fulldeps/proc-macro/attr-on-trait.rs
new file mode 100644
index 0000000000000..8ba38875eff5b
--- /dev/null
+++ b/src/test/run-pass-fulldeps/proc-macro/attr-on-trait.rs
@@ -0,0 +1,28 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// aux-build:attr-on-trait.rs
+
+#![feature(proc_macro)]
+
+extern crate attr_on_trait;
+
+trait Foo {
+    #[attr_on_trait::foo]
+    fn foo() {}
+}
+
+impl Foo for i32 {
+    fn foo(&self) {}
+}
+
+fn main() {
+    3i32.foo();
+}
diff --git a/src/test/run-pass-fulldeps/proc-macro/auxiliary/attr-on-trait.rs b/src/test/run-pass-fulldeps/proc-macro/auxiliary/attr-on-trait.rs
new file mode 100644
index 0000000000000..8e9770340276b
--- /dev/null
+++ b/src/test/run-pass-fulldeps/proc-macro/auxiliary/attr-on-trait.rs
@@ -0,0 +1,25 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// no-prefer-dynamic
+
+#![feature(proc_macro)]
+#![crate_type = "proc-macro"]
+
+extern crate proc_macro;
+
+use proc_macro::TokenStream;
+
+#[proc_macro_attribute]
+pub fn foo(attr: TokenStream, item: TokenStream) -> TokenStream {
+    drop(attr);
+    assert_eq!(item.to_string(), "fn foo() { }");
+    "fn foo(&self);".parse().unwrap()
+}
diff --git a/src/test/run-pass/discriminant_value-wrapper.rs b/src/test/run-pass/discriminant_value-wrapper.rs
index 2dbda0be18d98..d7a32423710fd 100644
--- a/src/test/run-pass/discriminant_value-wrapper.rs
+++ b/src/test/run-pass/discriminant_value-wrapper.rs
@@ -8,8 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(discriminant_value)]
-
 use std::mem;
 
 enum ADT {
diff --git a/src/test/run-pass/generator/auxiliary/xcrate-reachable.rs b/src/test/run-pass/generator/auxiliary/xcrate-reachable.rs
new file mode 100644
index 0000000000000..a6a2a2d081e1f
--- /dev/null
+++ b/src/test/run-pass/generator/auxiliary/xcrate-reachable.rs
@@ -0,0 +1,24 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(conservative_impl_trait, generators, generator_trait)]
+
+use std::ops::Generator;
+
+fn msg() -> u32 {
+    0
+}
+
+pub fn foo() -> impl Generator<Yield=(), Return=u32> {
+    || {
+        yield;
+        return msg();
+    }
+}
diff --git a/src/test/run-pass/generator/auxiliary/xcrate.rs b/src/test/run-pass/generator/auxiliary/xcrate.rs
new file mode 100644
index 0000000000000..f6878e64fbf93
--- /dev/null
+++ b/src/test/run-pass/generator/auxiliary/xcrate.rs
@@ -0,0 +1,27 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(generators, generator_trait, conservative_impl_trait)]
+
+use std::ops::Generator;
+
+pub fn foo() -> impl Generator<Yield = (), Return = ()> {
+    || {
+        if false {
+            yield;
+        }
+    }
+}
+
+pub fn bar<T: 'static>(t: T) -> Box<Generator<Yield = T, Return = ()>> {
+    Box::new(|| {
+        yield t;
+    })
+}
diff --git a/src/test/run-pass/generator/conditional-drop.rs b/src/test/run-pass/generator/conditional-drop.rs
new file mode 100644
index 0000000000000..8329684e1a39b
--- /dev/null
+++ b/src/test/run-pass/generator/conditional-drop.rs
@@ -0,0 +1,65 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(generators, generator_trait)]
+
+use std::ops::Generator;
+use std::sync::atomic::{AtomicUsize, ATOMIC_USIZE_INIT, Ordering};
+
+static A: AtomicUsize = ATOMIC_USIZE_INIT;
+
+struct B;
+
+impl Drop for B {
+    fn drop(&mut self) {
+        A.fetch_add(1, Ordering::SeqCst);
+    }
+}
+
+
+fn test() -> bool { true }
+fn test2() -> bool { false }
+
+fn main() {
+    t1();
+    t2();
+}
+
+fn t1() {
+    let mut a = || {
+        let b = B;
+        if test() {
+            drop(b);
+        }
+        yield;
+    };
+
+    let n = A.load(Ordering::SeqCst);
+    a.resume();
+    assert_eq!(A.load(Ordering::SeqCst), n + 1);
+    a.resume();
+    assert_eq!(A.load(Ordering::SeqCst), n + 1);
+}
+
+fn t2() {
+    let mut a = || {
+        let b = B;
+        if test2() {
+            drop(b);
+        }
+        yield;
+    };
+
+    let n = A.load(Ordering::SeqCst);
+    a.resume();
+    assert_eq!(A.load(Ordering::SeqCst), n);
+    a.resume();
+    assert_eq!(A.load(Ordering::SeqCst), n + 1);
+}
diff --git a/src/test/run-pass/generator/control-flow.rs b/src/test/run-pass/generator/control-flow.rs
new file mode 100644
index 0000000000000..60a00b4e46756
--- /dev/null
+++ b/src/test/run-pass/generator/control-flow.rs
@@ -0,0 +1,56 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(generators, generator_trait)]
+
+use std::ops::{GeneratorState, Generator};
+
+fn finish<T>(mut amt: usize, mut t: T) -> T::Return
+    where T: Generator<Yield = ()>
+{
+    loop {
+        match t.resume() {
+            GeneratorState::Yielded(()) => amt = amt.checked_sub(1).unwrap(),
+            GeneratorState::Complete(ret) => {
+                assert_eq!(amt, 0);
+                return ret
+            }
+        }
+    }
+
+}
+
+fn main() {
+    finish(1, || yield);
+    finish(8, || {
+        for _ in 0..8 {
+            yield;
+        }
+    });
+    finish(1, || {
+        if true {
+            yield;
+        } else {
+        }
+    });
+    finish(1, || {
+        if false {
+        } else {
+            yield;
+        }
+    });
+    finish(2, || {
+        if { yield; false } {
+            yield;
+            panic!()
+        }
+        yield
+    });
+}
diff --git a/src/test/run-pass/generator/drop-env.rs b/src/test/run-pass/generator/drop-env.rs
new file mode 100644
index 0000000000000..ac42a25899dbb
--- /dev/null
+++ b/src/test/run-pass/generator/drop-env.rs
@@ -0,0 +1,70 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(generators, generator_trait)]
+
+use std::ops::Generator;
+use std::sync::atomic::{AtomicUsize, ATOMIC_USIZE_INIT, Ordering};
+
+static A: AtomicUsize = ATOMIC_USIZE_INIT;
+
+struct B;
+
+impl Drop for B {
+    fn drop(&mut self) {
+        A.fetch_add(1, Ordering::SeqCst);
+    }
+}
+
+fn main() {
+    t1();
+    t2();
+    t3();
+}
+
+fn t1() {
+    let b = B;
+    let mut foo = || {
+        yield;
+        drop(b);
+    };
+
+    let n = A.load(Ordering::SeqCst);
+    drop(foo.resume());
+    assert_eq!(A.load(Ordering::SeqCst), n);
+    drop(foo);
+    assert_eq!(A.load(Ordering::SeqCst), n + 1);
+}
+
+fn t2() {
+    let b = B;
+    let mut foo = || {
+        yield b;
+    };
+
+    let n = A.load(Ordering::SeqCst);
+    drop(foo.resume());
+    assert_eq!(A.load(Ordering::SeqCst), n + 1);
+    drop(foo);
+    assert_eq!(A.load(Ordering::SeqCst), n + 1);
+}
+
+fn t3() {
+    let b = B;
+    let foo = || {
+        yield;
+        drop(b);
+    };
+
+    let n = A.load(Ordering::SeqCst);
+    assert_eq!(A.load(Ordering::SeqCst), n);
+    drop(foo);
+    assert_eq!(A.load(Ordering::SeqCst), n + 1);
+}
diff --git a/src/test/run-pass/generator/iterator-count.rs b/src/test/run-pass/generator/iterator-count.rs
new file mode 100644
index 0000000000000..9afe95f9e865c
--- /dev/null
+++ b/src/test/run-pass/generator/iterator-count.rs
@@ -0,0 +1,48 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(generators, generator_trait, conservative_impl_trait)]
+
+use std::ops::{GeneratorState, Generator};
+
+struct W<T>(T);
+
+impl<T: Generator<Return = ()>> Iterator for W<T> {
+    type Item = T::Yield;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        match self.0.resume() {
+            GeneratorState::Complete(..) => None,
+            GeneratorState::Yielded(v) => Some(v),
+        }
+    }
+}
+
+fn test() -> impl Generator<Return=(), Yield=u8> {
+    || {
+        for i in 1..6 {
+            yield i
+        }
+    }
+}
+
+fn main() {
+    let end = 11;
+
+    let closure_test = |start| {
+        move || {
+            for i in start..end {
+                yield i
+            }
+        }
+    };
+
+    assert!(W(test()).chain(W(closure_test(6))).eq(1..11));
+}
diff --git a/src/test/run-pass/generator/panic-drops.rs b/src/test/run-pass/generator/panic-drops.rs
new file mode 100644
index 0000000000000..53cd3235d9d0c
--- /dev/null
+++ b/src/test/run-pass/generator/panic-drops.rs
@@ -0,0 +1,62 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(generators, generator_trait)]
+
+use std::ops::Generator;
+use std::panic;
+use std::sync::atomic::{AtomicUsize, ATOMIC_USIZE_INIT, Ordering};
+
+static A: AtomicUsize = ATOMIC_USIZE_INIT;
+
+struct B;
+
+impl Drop for B {
+    fn drop(&mut self) {
+        A.fetch_add(1, Ordering::SeqCst);
+    }
+}
+
+fn bool_true() -> bool {
+    true
+}
+
+fn main() {
+    let b = B;
+    let mut foo = || {
+        if bool_true() {
+            panic!();
+        }
+        drop(b);
+        yield;
+    };
+
+    assert_eq!(A.load(Ordering::SeqCst), 0);
+    let res = panic::catch_unwind(panic::AssertUnwindSafe(|| {
+        foo.resume()
+    }));
+    assert!(res.is_err());
+    assert_eq!(A.load(Ordering::SeqCst), 1);
+
+    let mut foo = || {
+        if bool_true() {
+            panic!();
+        }
+        drop(B);
+        yield;
+    };
+
+    assert_eq!(A.load(Ordering::SeqCst), 1);
+    let res = panic::catch_unwind(panic::AssertUnwindSafe(|| {
+        foo.resume()
+    }));
+    assert!(res.is_err());
+    assert_eq!(A.load(Ordering::SeqCst), 1);
+}
diff --git a/src/test/run-pass/generator/panic-safe.rs b/src/test/run-pass/generator/panic-safe.rs
new file mode 100644
index 0000000000000..a583f42b93d8c
--- /dev/null
+++ b/src/test/run-pass/generator/panic-safe.rs
@@ -0,0 +1,35 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(generators, generator_trait)]
+
+use std::ops::Generator;
+use std::panic;
+
+fn main() {
+    let mut foo = || {
+        if true {
+            panic!();
+        }
+        yield;
+    };
+
+    let res = panic::catch_unwind(panic::AssertUnwindSafe(|| {
+        foo.resume()
+    }));
+    assert!(res.is_err());
+
+    for _ in 0..10 {
+        let res = panic::catch_unwind(panic::AssertUnwindSafe(|| {
+            foo.resume()
+        }));
+        assert!(res.is_err());
+    }
+}
diff --git a/src/test/run-pass/generator/resume-after-return.rs b/src/test/run-pass/generator/resume-after-return.rs
new file mode 100644
index 0000000000000..b2e2a3e7e9d5b
--- /dev/null
+++ b/src/test/run-pass/generator/resume-after-return.rs
@@ -0,0 +1,33 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(generators, generator_trait)]
+
+use std::ops::{GeneratorState, Generator};
+use std::panic;
+
+fn main() {
+    let mut foo = || {
+        if true {
+            return
+        }
+        yield;
+    };
+
+    match foo.resume() {
+        GeneratorState::Complete(()) => {}
+        s => panic!("bad state: {:?}", s),
+    }
+
+    match panic::catch_unwind(move || foo.resume()) {
+        Ok(_) => panic!("generator successfully resumed"),
+        Err(_) => {}
+    }
+}
diff --git a/src/test/run-pass/generator/smoke.rs b/src/test/run-pass/generator/smoke.rs
new file mode 100644
index 0000000000000..e9bdfbf28ea9c
--- /dev/null
+++ b/src/test/run-pass/generator/smoke.rs
@@ -0,0 +1,181 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// ignore-emscripten
+// compile-flags: --test
+
+#![feature(generators, generator_trait)]
+
+use std::ops::{GeneratorState, Generator};
+use std::thread;
+
+#[test]
+fn simple() {
+    let mut foo = || {
+        if false {
+            yield;
+        }
+    };
+
+    match foo.resume() {
+        GeneratorState::Complete(()) => {}
+        s => panic!("bad state: {:?}", s),
+    }
+}
+
+#[test]
+fn return_capture() {
+    let a = String::from("foo");
+    let mut foo = || {
+        if false {
+            yield;
+        }
+        a
+    };
+
+    match foo.resume() {
+        GeneratorState::Complete(ref s) if *s == "foo" => {}
+        s => panic!("bad state: {:?}", s),
+    }
+}
+
+#[test]
+fn simple_yield() {
+    let mut foo = || {
+        yield;
+    };
+
+    match foo.resume() {
+        GeneratorState::Yielded(()) => {}
+        s => panic!("bad state: {:?}", s),
+    }
+    match foo.resume() {
+        GeneratorState::Complete(()) => {}
+        s => panic!("bad state: {:?}", s),
+    }
+}
+
+#[test]
+fn yield_capture() {
+    let b = String::from("foo");
+    let mut foo = || {
+        yield b;
+    };
+
+    match foo.resume() {
+        GeneratorState::Yielded(ref s) if *s == "foo" => {}
+        s => panic!("bad state: {:?}", s),
+    }
+    match foo.resume() {
+        GeneratorState::Complete(()) => {}
+        s => panic!("bad state: {:?}", s),
+    }
+}
+
+#[test]
+fn simple_yield_value() {
+    let mut foo = || {
+        yield String::from("bar");
+        return String::from("foo")
+    };
+
+    match foo.resume() {
+        GeneratorState::Yielded(ref s) if *s == "bar" => {}
+        s => panic!("bad state: {:?}", s),
+    }
+    match foo.resume() {
+        GeneratorState::Complete(ref s) if *s == "foo" => {}
+        s => panic!("bad state: {:?}", s),
+    }
+}
+
+#[test]
+fn return_after_yield() {
+    let a = String::from("foo");
+    let mut foo = || {
+        yield;
+        return a
+    };
+
+    match foo.resume() {
+        GeneratorState::Yielded(()) => {}
+        s => panic!("bad state: {:?}", s),
+    }
+    match foo.resume() {
+        GeneratorState::Complete(ref s) if *s == "foo" => {}
+        s => panic!("bad state: {:?}", s),
+    }
+}
+
+#[test]
+fn send_and_sync() {
+    assert_send_sync(|| {
+        yield
+    });
+    assert_send_sync(|| {
+        yield String::from("foo");
+    });
+    assert_send_sync(|| {
+        yield;
+        return String::from("foo");
+    });
+    let a = 3;
+    assert_send_sync(|| {
+        yield a;
+        return
+    });
+    let a = 3;
+    assert_send_sync(move || {
+        yield a;
+        return
+    });
+    let a = String::from("a");
+    assert_send_sync(|| {
+        yield ;
+        drop(a);
+        return
+    });
+    let a = String::from("a");
+    assert_send_sync(move || {
+        yield ;
+        drop(a);
+        return
+    });
+
+    fn assert_send_sync<T: Send + Sync>(_: T) {}
+}
+
+#[test]
+fn send_over_threads() {
+    let mut foo = || { yield };
+    thread::spawn(move || {
+        match foo.resume() {
+            GeneratorState::Yielded(()) => {}
+            s => panic!("bad state: {:?}", s),
+        }
+        match foo.resume() {
+            GeneratorState::Complete(()) => {}
+            s => panic!("bad state: {:?}", s),
+        }
+    }).join().unwrap();
+
+    let a = String::from("a");
+    let mut foo = || { yield a };
+    thread::spawn(move || {
+        match foo.resume() {
+            GeneratorState::Yielded(ref s) if *s == "a" => {}
+            s => panic!("bad state: {:?}", s),
+        }
+        match foo.resume() {
+            GeneratorState::Complete(()) => {}
+            s => panic!("bad state: {:?}", s),
+        }
+    }).join().unwrap();
+}
diff --git a/src/test/run-pass/generator/xcrate-reachable.rs b/src/test/run-pass/generator/xcrate-reachable.rs
new file mode 100644
index 0000000000000..dff5e08b9c20e
--- /dev/null
+++ b/src/test/run-pass/generator/xcrate-reachable.rs
@@ -0,0 +1,21 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// aux-build:xcrate-reachable.rs
+
+#![feature(conservative_impl_trait, generator_trait)]
+
+extern crate xcrate_reachable as foo;
+
+use std::ops::Generator;
+
+fn main() {
+    foo::foo().resume();
+}
diff --git a/src/test/run-pass/generator/xcrate.rs b/src/test/run-pass/generator/xcrate.rs
new file mode 100644
index 0000000000000..dc7a6fdef9c7e
--- /dev/null
+++ b/src/test/run-pass/generator/xcrate.rs
@@ -0,0 +1,37 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// aux-build:xcrate.rs
+
+#![feature(generators, generator_trait)]
+
+extern crate xcrate;
+
+use std::ops::{GeneratorState, Generator};
+
+fn main() {
+    let mut foo = xcrate::foo();
+
+    match foo.resume() {
+        GeneratorState::Complete(()) => {}
+        s => panic!("bad state: {:?}", s),
+    }
+
+    let mut foo = xcrate::bar(3);
+
+    match foo.resume() {
+        GeneratorState::Yielded(3) => {}
+        s => panic!("bad state: {:?}", s),
+    }
+    match foo.resume() {
+        GeneratorState::Complete(()) => {}
+        s => panic!("bad state: {:?}", s),
+    }
+}
diff --git a/src/test/run-pass/generator/yield-subtype.rs b/src/test/run-pass/generator/yield-subtype.rs
new file mode 100644
index 0000000000000..5ff070f311e01
--- /dev/null
+++ b/src/test/run-pass/generator/yield-subtype.rs
@@ -0,0 +1,23 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(generators)]
+
+fn bar<'a>() {
+    let a: &'static str = "hi";
+    let b: &'a str = a;
+
+    || {
+        yield a;
+        yield b;
+    };
+}
+
+fn main() {}
\ No newline at end of file
diff --git a/src/test/run-pass/import-crate-with-invalid-spans/main.rs b/src/test/run-pass/import-crate-with-invalid-spans/main.rs
index 39c175f60da41..2f80a0954dc0a 100644
--- a/src/test/run-pass/import-crate-with-invalid-spans/main.rs
+++ b/src/test/run-pass/import-crate-with-invalid-spans/main.rs
@@ -16,7 +16,7 @@ extern crate crate_with_invalid_spans;
 
 fn main() {
     // The AST of `exported_generic` stored in crate_with_invalid_spans's
-    // metadata should contain an invalid span where span.lo > span.hi.
+    // metadata should contain an invalid span where span.lo() > span.hi().
     // Let's make sure the compiler doesn't crash when encountering this.
     let _ = crate_with_invalid_spans::exported_generic(32u32, 7u32);
 }
diff --git a/src/test/run-pass/method-argument-inference-associated-type.rs b/src/test/run-pass/method-argument-inference-associated-type.rs
new file mode 100644
index 0000000000000..76b8cf92329d1
--- /dev/null
+++ b/src/test/run-pass/method-argument-inference-associated-type.rs
@@ -0,0 +1,37 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+pub struct ClientMap;
+pub struct ClientMap2;
+
+pub trait Service {
+    type Request;
+    fn call(&self, _req: Self::Request);
+}
+
+pub struct S<T>(T);
+
+impl Service for ClientMap {
+    type Request = S<Box<Fn(i32)>>;
+    fn call(&self, _req: Self::Request) {}
+}
+
+
+impl Service for ClientMap2 {
+    type Request = (Box<Fn(i32)>,);
+    fn call(&self, _req: Self::Request) {}
+}
+
+
+fn main() {
+    ClientMap.call(S { 0: Box::new(|_msgid| ()) });
+    ClientMap.call(S(Box::new(|_msgid| ())));
+    ClientMap2.call((Box::new(|_msgid| ()),));
+}
diff --git a/src/test/run-pass/rvalue-static-promotion.rs b/src/test/run-pass/rvalue-static-promotion.rs
index e57491930a45b..acf96b566df84 100644
--- a/src/test/run-pass/rvalue-static-promotion.rs
+++ b/src/test/run-pass/rvalue-static-promotion.rs
@@ -8,8 +8,20 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#[allow(unused_variables)]
+use std::cell::Cell;
+
+const NONE_CELL_STRING: Option<Cell<String>> = None;
+
+struct Foo<T>(T);
+impl<T> Foo<T> {
+    const FOO: Option<Box<T>> = None;
+}
+
 fn main() {
-    let x: &'static u32 = &42;
-    let y: &'static Option<u32> = &None;
+    let _: &'static u32 = &42;
+    let _: &'static Option<u32> = &None;
+
+    // We should be able to peek at consts and see they're None.
+    let _: &'static Option<Cell<String>> = &NONE_CELL_STRING;
+    let _: &'static Option<Box<()>> = &Foo::FOO;
 }
diff --git a/src/test/run-pass/semistatement-in-lambda.rs b/src/test/run-pass/semistatement-in-lambda.rs
new file mode 100644
index 0000000000000..0fc5fe498a62d
--- /dev/null
+++ b/src/test/run-pass/semistatement-in-lambda.rs
@@ -0,0 +1,19 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+
+pub fn main() {
+    // Test that lambdas behave as unary expressions with block-like expressions
+    -if true { 1 } else { 2 } * 3;
+    || if true { 1 } else { 2 } * 3;
+
+    // The following is invalid and parses as `if true { 1 } else { 2 }; *3`
+    // if true { 1 } else { 2 } * 3
+}
diff --git a/src/test/compile-fail/unboxed-closures-infer-explicit-call-too-early.rs b/src/test/run-pass/unboxed-closures-infer-explicit-call-early.rs
similarity index 79%
rename from src/test/compile-fail/unboxed-closures-infer-explicit-call-too-early.rs
rename to src/test/run-pass/unboxed-closures-infer-explicit-call-early.rs
index 62f6ee56ca5de..028f2e9375b3c 100644
--- a/src/test/compile-fail/unboxed-closures-infer-explicit-call-too-early.rs
+++ b/src/test/run-pass/unboxed-closures-infer-explicit-call-early.rs
@@ -8,8 +8,10 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+#![feature(fn_traits)]
+
 fn main() {
-    let mut zero = || {};
-    let () = zero.call_mut(());
-    //~^ ERROR we have not yet inferred what kind of closure it is
+    let mut zero = || 0;
+    let x = zero.call_mut(());
+    assert_eq!(x, 0);
 }
diff --git a/src/test/rustdoc/issue-41783.rs b/src/test/rustdoc/issue-41783.rs
index 3933b8bcbb8fd..991cf4cf2b375 100644
--- a/src/test/rustdoc/issue-41783.rs
+++ b/src/test/rustdoc/issue-41783.rs
@@ -12,8 +12,10 @@
 // @!has - 'space'
 // @!has - 'comment'
 // @has - '# <span class="ident">single'
-// @has - '#<span class="attribute"># <span class="ident">double</span>'
-// @has - '#<span class="attribute">#<span class="attribute"># <span class="ident">triple</span>'
+// @has - '## <span class="ident">double</span>'
+// @has - '### <span class="ident">triple</span>'
+// @has - '<span class="attribute">#[<span class="ident">outer</span>]</span>'
+// @has - '<span class="attribute">#![<span class="ident">inner</span>]</span>'
 
 /// ```no_run
 /// # # space
@@ -21,5 +23,7 @@
 /// ## single
 /// ### double
 /// #### triple
+/// ##[outer]
+/// ##![inner]
 /// ```
 pub struct Foo;
diff --git a/src/test/ui-fulldeps/proc-macro/auxiliary/three-equals.rs b/src/test/ui-fulldeps/proc-macro/auxiliary/three-equals.rs
new file mode 100644
index 0000000000000..6fca32fece1d4
--- /dev/null
+++ b/src/test/ui-fulldeps/proc-macro/auxiliary/three-equals.rs
@@ -0,0 +1,56 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// no-prefer-dynamic
+#![feature(proc_macro)]
+#![crate_type = "proc-macro"]
+
+extern crate proc_macro;
+
+use proc_macro::{TokenStream, TokenNode, Span, Diagnostic};
+
+fn parse(input: TokenStream) -> Result<(), Diagnostic> {
+    let mut count = 0;
+    let mut last_span = Span::default();
+    for tree in input {
+        let span = tree.span;
+        if count >= 3 {
+            return Err(span.error(format!("expected EOF, found `{}`.", tree))
+                           .span_note(last_span, "last good input was here")
+                           .help("input must be: `===`"))
+        }
+
+        if let TokenNode::Op('=', _) = tree.kind {
+            count += 1;
+        } else {
+            return Err(span.error(format!("expected `=`, found `{}`.", tree)));
+        }
+
+        last_span = span;
+    }
+
+    if count < 3 {
+        return Err(Span::default()
+                       .error(format!("found {} equal signs, need exactly 3", count))
+                       .help("input must be: `===`"))
+    }
+
+    Ok(())
+}
+
+#[proc_macro]
+pub fn three_equals(input: TokenStream) -> TokenStream {
+    if let Err(diag) = parse(input) {
+        diag.emit();
+        return TokenStream::empty();
+    }
+
+    "3".parse().unwrap()
+}
diff --git a/src/test/ui-fulldeps/proc-macro/three-equals.rs b/src/test/ui-fulldeps/proc-macro/three-equals.rs
new file mode 100644
index 0000000000000..016e05c51f507
--- /dev/null
+++ b/src/test/ui-fulldeps/proc-macro/three-equals.rs
@@ -0,0 +1,38 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// aux-build:three-equals.rs
+// ignore-stage1
+
+#![feature(proc_macro)]
+
+extern crate three_equals;
+
+use three_equals::three_equals;
+
+fn main() {
+    // This one is okay.
+    three_equals!(===);
+
+    // Need exactly three equals.
+    three_equals!(==);
+
+    // Need exactly three equals.
+    three_equals!(=====);
+
+    // Only equals accepted.
+    three_equals!(abc);
+
+    // Only equals accepted.
+    three_equals!(!!);
+
+    // Only three characters expected.
+    three_equals!(===a);
+}
diff --git a/src/test/ui-fulldeps/proc-macro/three-equals.stderr b/src/test/ui-fulldeps/proc-macro/three-equals.stderr
new file mode 100644
index 0000000000000..1afe0be280009
--- /dev/null
+++ b/src/test/ui-fulldeps/proc-macro/three-equals.stderr
@@ -0,0 +1,48 @@
+error: found 2 equal signs, need exactly 3
+  --> $DIR/three-equals.rs:25:5
+   |
+25 |     three_equals!(==);
+   |     ^^^^^^^^^^^^^^^^^^
+   |
+   = help: input must be: `===`
+
+error: expected EOF, found `=`.
+  --> $DIR/three-equals.rs:28:21
+   |
+28 |     three_equals!(=====);
+   |                     ^^
+   |
+note: last good input was here
+  --> $DIR/three-equals.rs:28:21
+   |
+28 |     three_equals!(=====);
+   |                     ^^
+   = help: input must be: `===`
+
+error: expected `=`, found `abc`.
+  --> $DIR/three-equals.rs:31:19
+   |
+31 |     three_equals!(abc);
+   |                   ^^^
+
+error: expected `=`, found `!`.
+  --> $DIR/three-equals.rs:34:19
+   |
+34 |     three_equals!(!!);
+   |                   ^
+
+error: expected EOF, found `a`.
+  --> $DIR/three-equals.rs:37:22
+   |
+37 |     three_equals!(===a);
+   |                      ^
+   |
+note: last good input was here
+  --> $DIR/three-equals.rs:37:21
+   |
+37 |     three_equals!(===a);
+   |                     ^
+   = help: input must be: `===`
+
+error: aborting due to 5 previous errors
+
diff --git a/src/test/ui/generator/borrowing.rs b/src/test/ui/generator/borrowing.rs
new file mode 100644
index 0000000000000..de10bdef4aee0
--- /dev/null
+++ b/src/test/ui/generator/borrowing.rs
@@ -0,0 +1,30 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(generators, generator_trait)]
+
+use std::ops::Generator;
+
+fn main() {
+    let _b = {
+        let a = 3;
+        (|| yield &a).resume()
+        //~^ ERROR: `a` does not live long enough
+    };
+
+    let _b = {
+        let a = 3;
+        || {
+            yield &a
+            //~^ ERROR: `a` does not live long enough
+        }
+    };
+}
+
diff --git a/src/test/ui/generator/borrowing.stderr b/src/test/ui/generator/borrowing.stderr
new file mode 100644
index 0000000000000..0ed7e1f99027d
--- /dev/null
+++ b/src/test/ui/generator/borrowing.stderr
@@ -0,0 +1,29 @@
+error[E0597]: `a` does not live long enough
+  --> $DIR/borrowing.rs:18:20
+   |
+18 |         (|| yield &a).resume()
+   |          --        ^ does not live long enough
+   |          |
+   |          capture occurs here
+19 |         //~^ ERROR: `a` does not live long enough
+20 |     };
+   |     - borrowed value only lives until here
+...
+29 | }
+   | - borrowed value needs to live until here
+
+error[E0597]: `a` does not live long enough
+  --> $DIR/borrowing.rs:25:20
+   |
+24 |         || {
+   |         -- capture occurs here
+25 |             yield &a
+   |                    ^ does not live long enough
+...
+28 |     };
+   |     - borrowed value only lives until here
+29 | }
+   | - borrowed value needs to live until here
+
+error: aborting due to 2 previous errors
+
diff --git a/src/test/ui/generator/no-arguments-on-generators.rs b/src/test/ui/generator/no-arguments-on-generators.rs
new file mode 100644
index 0000000000000..a7e98fe450927
--- /dev/null
+++ b/src/test/ui/generator/no-arguments-on-generators.rs
@@ -0,0 +1,17 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(generators)]
+
+fn main() {
+    let gen = |start| { //~ ERROR generators cannot have explicit arguments
+        yield;
+    };
+}
diff --git a/src/test/ui/generator/no-arguments-on-generators.stderr b/src/test/ui/generator/no-arguments-on-generators.stderr
new file mode 100644
index 0000000000000..4d2e228685ae3
--- /dev/null
+++ b/src/test/ui/generator/no-arguments-on-generators.stderr
@@ -0,0 +1,8 @@
+error[E0628]: generators cannot have explicit arguments
+  --> $DIR/no-arguments-on-generators.rs:14:15
+   |
+14 |     let gen = |start| { //~ ERROR generators cannot have explicit arguments
+   |               ^^^^^^^
+
+error: aborting due to previous error
+
diff --git a/src/test/ui/generator/not-send-sync.rs b/src/test/ui/generator/not-send-sync.rs
new file mode 100644
index 0000000000000..0419758d8ea17
--- /dev/null
+++ b/src/test/ui/generator/not-send-sync.rs
@@ -0,0 +1,31 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(generators)]
+
+use std::cell::Cell;
+
+fn main() {
+    fn assert_sync<T: Sync>(_: T) {}
+    fn assert_send<T: Send>(_: T) {}
+
+    assert_sync(|| {
+        //~^ ERROR: Sync` is not satisfied
+        let a = Cell::new(2);
+        yield;
+    });
+
+    let a = Cell::new(2);
+    assert_send(|| {
+        //~^ ERROR: Sync` is not satisfied
+        drop(&a);
+        yield;
+    });
+}
diff --git a/src/test/ui/generator/not-send-sync.stderr b/src/test/ui/generator/not-send-sync.stderr
new file mode 100644
index 0000000000000..e0c32a95e0d9b
--- /dev/null
+++ b/src/test/ui/generator/not-send-sync.stderr
@@ -0,0 +1,24 @@
+error[E0277]: the trait bound `std::cell::Cell<i32>: std::marker::Sync` is not satisfied
+  --> $DIR/not-send-sync.rs:26:5
+   |
+26 |     assert_send(|| {
+   |     ^^^^^^^^^^^ `std::cell::Cell<i32>` cannot be shared between threads safely
+   |
+   = help: the trait `std::marker::Sync` is not implemented for `std::cell::Cell<i32>`
+   = note: required because of the requirements on the impl of `std::marker::Send` for `&std::cell::Cell<i32>`
+   = note: required because it appears within the type `[generator@$DIR/not-send-sync.rs:26:17: 30:6 a:&std::cell::Cell<i32> _]`
+   = note: required by `main::assert_send`
+
+error[E0277]: the trait bound `std::cell::Cell<i32>: std::marker::Sync` is not satisfied in `[generator@$DIR/not-send-sync.rs:19:17: 23:6 ((), std::cell::Cell<i32>)]`
+  --> $DIR/not-send-sync.rs:19:5
+   |
+19 |     assert_sync(|| {
+   |     ^^^^^^^^^^^ `std::cell::Cell<i32>` cannot be shared between threads safely
+   |
+   = help: within `[generator@$DIR/not-send-sync.rs:19:17: 23:6 ((), std::cell::Cell<i32>)]`, the trait `std::marker::Sync` is not implemented for `std::cell::Cell<i32>`
+   = note: required because it appears within the type `((), std::cell::Cell<i32>)`
+   = note: required because it appears within the type `[generator@$DIR/not-send-sync.rs:19:17: 23:6 ((), std::cell::Cell<i32>)]`
+   = note: required by `main::assert_sync`
+
+error: aborting due to 2 previous errors
+
diff --git a/src/test/ui/generator/ref-escapes-but-not-over-yield.rs b/src/test/ui/generator/ref-escapes-but-not-over-yield.rs
new file mode 100644
index 0000000000000..87edbb22baae1
--- /dev/null
+++ b/src/test/ui/generator/ref-escapes-but-not-over-yield.rs
@@ -0,0 +1,28 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(generators, generator_trait)]
+
+use std::ops::{GeneratorState, Generator};
+use std::cell::Cell;
+
+fn foo(x: &i32) {
+    // In this case, a reference to `b` escapes the generator, but not
+    // because of a yield. We see that there is no yield in the scope of
+    // `b` and give the more generic error message.
+    let mut a = &3;
+    let mut b = move || {
+        yield();
+        let b = 5;
+        a = &b; //~ ERROR
+    };
+}
+
+fn main() { }
diff --git a/src/test/ui/generator/ref-escapes-but-not-over-yield.stderr b/src/test/ui/generator/ref-escapes-but-not-over-yield.stderr
new file mode 100644
index 0000000000000..e30d28c2db83b
--- /dev/null
+++ b/src/test/ui/generator/ref-escapes-but-not-over-yield.stderr
@@ -0,0 +1,12 @@
+error[E0597]: `b` does not live long enough
+  --> $DIR/ref-escapes-but-not-over-yield.rs:25:5
+   |
+24 |         a = &b; //~ ERROR
+   |              - borrow occurs here
+25 |     };
+   |     ^ `b` dropped here while still borrowed
+26 | }
+   | - borrowed value needs to live until here
+
+error: aborting due to previous error
+
diff --git a/src/test/ui/generator/yield-in-args-rev.rs b/src/test/ui/generator/yield-in-args-rev.rs
new file mode 100644
index 0000000000000..fb0e68136f544
--- /dev/null
+++ b/src/test/ui/generator/yield-in-args-rev.rs
@@ -0,0 +1,24 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(generators)]
+
+fn foo(_a: (), _b: &bool) {}
+
+// Some examples that probably *could* be accepted, but which we reject for now.
+
+fn bar() {
+    || {
+        let b = true;
+        foo(yield, &b); //~ ERROR
+    };
+}
+
+fn main() { }
diff --git a/src/test/ui/generator/yield-in-args-rev.stderr b/src/test/ui/generator/yield-in-args-rev.stderr
new file mode 100644
index 0000000000000..157f896820906
--- /dev/null
+++ b/src/test/ui/generator/yield-in-args-rev.stderr
@@ -0,0 +1,10 @@
+error[E0626]: borrow may still be in use when generator yields
+  --> $DIR/yield-in-args-rev.rs:20:21
+   |
+20 |         foo(yield, &b); //~ ERROR
+   |             -----   ^
+   |             |
+   |             possible yield occurs here
+
+error: aborting due to previous error
+
diff --git a/src/test/ui/generator/yield-in-args.rs b/src/test/ui/generator/yield-in-args.rs
new file mode 100644
index 0000000000000..faeb4b1feb28d
--- /dev/null
+++ b/src/test/ui/generator/yield-in-args.rs
@@ -0,0 +1,20 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(generators)]
+
+fn foo(_b: &bool, _a: ()) {}
+
+fn main() {
+    || {
+        let b = true;
+        foo(&b, yield); //~ ERROR
+    };
+}
diff --git a/src/test/ui/generator/yield-in-args.stderr b/src/test/ui/generator/yield-in-args.stderr
new file mode 100644
index 0000000000000..06561853dee8c
--- /dev/null
+++ b/src/test/ui/generator/yield-in-args.stderr
@@ -0,0 +1,8 @@
+error[E0626]: borrow may still be in use when generator yields
+  --> $DIR/yield-in-args.rs:18:14
+   |
+18 |         foo(&b, yield); //~ ERROR
+   |              ^  ----- possible yield occurs here
+
+error: aborting due to previous error
+
diff --git a/src/test/ui/generator/yield-in-const.rs b/src/test/ui/generator/yield-in-const.rs
new file mode 100644
index 0000000000000..e166d26515975
--- /dev/null
+++ b/src/test/ui/generator/yield-in-const.rs
@@ -0,0 +1,14 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(generators)]
+
+const A: u8 = { yield 3u8; 3u8};
+//~^ ERROR yield statement outside
diff --git a/src/test/ui/generator/yield-in-const.stderr b/src/test/ui/generator/yield-in-const.stderr
new file mode 100644
index 0000000000000..8a265c065b988
--- /dev/null
+++ b/src/test/ui/generator/yield-in-const.stderr
@@ -0,0 +1,10 @@
+error[E0601]: main function not found
+
+error[E0627]: yield statement outside of generator literal
+  --> $DIR/yield-in-const.rs:13:17
+   |
+13 | const A: u8 = { yield 3u8; 3u8};
+   |                 ^^^^^^^^^
+
+error: aborting due to 2 previous errors
+
diff --git a/src/test/ui/generator/yield-in-function.rs b/src/test/ui/generator/yield-in-function.rs
new file mode 100644
index 0000000000000..2f6c5a9ef754c
--- /dev/null
+++ b/src/test/ui/generator/yield-in-function.rs
@@ -0,0 +1,14 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(generators)]
+
+fn main() { yield; }
+//~^ ERROR yield statement outside
diff --git a/src/test/ui/generator/yield-in-function.stderr b/src/test/ui/generator/yield-in-function.stderr
new file mode 100644
index 0000000000000..c6ee3b8e9e7e1
--- /dev/null
+++ b/src/test/ui/generator/yield-in-function.stderr
@@ -0,0 +1,8 @@
+error[E0627]: yield statement outside of generator literal
+  --> $DIR/yield-in-function.rs:13:13
+   |
+13 | fn main() { yield; }
+   |             ^^^^^
+
+error: aborting due to previous error
+
diff --git a/src/test/ui/generator/yield-in-static.rs b/src/test/ui/generator/yield-in-static.rs
new file mode 100644
index 0000000000000..823a2aa425e2c
--- /dev/null
+++ b/src/test/ui/generator/yield-in-static.rs
@@ -0,0 +1,14 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(generators)]
+
+static B: u8 = { yield 3u8; 3u8};
+//~^ ERROR yield statement outside
diff --git a/src/test/ui/generator/yield-in-static.stderr b/src/test/ui/generator/yield-in-static.stderr
new file mode 100644
index 0000000000000..d0575a0e47b3a
--- /dev/null
+++ b/src/test/ui/generator/yield-in-static.stderr
@@ -0,0 +1,10 @@
+error[E0601]: main function not found
+
+error[E0627]: yield statement outside of generator literal
+  --> $DIR/yield-in-static.rs:13:18
+   |
+13 | static B: u8 = { yield 3u8; 3u8};
+   |                  ^^^^^^^^^
+
+error: aborting due to 2 previous errors
+
diff --git a/src/test/ui/generator/yield-while-iterating.rs b/src/test/ui/generator/yield-while-iterating.rs
new file mode 100644
index 0000000000000..bc53448cb08e6
--- /dev/null
+++ b/src/test/ui/generator/yield-while-iterating.rs
@@ -0,0 +1,84 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(generators, generator_trait)]
+
+use std::ops::{GeneratorState, Generator};
+use std::cell::Cell;
+
+fn yield_during_iter_owned_data(x: Vec<i32>) {
+    // The generator owns `x`, so we error out when yielding with a
+    // reference to it.  This winds up becoming a rather confusing
+    // regionck error -- in particular, we would freeze with the
+    // reference in scope, and it doesn't live long enough.
+    let _b = move || {
+        for p in &x { //~ ERROR
+            yield();
+        }
+    };
+}
+
+fn yield_during_iter_borrowed_slice(x: &[i32]) {
+    let _b = move || {
+        for p in x {
+            yield();
+        }
+    };
+}
+
+fn yield_during_iter_borrowed_slice_2() {
+    let mut x = vec![22_i32];
+    let _b = || {
+        for p in &x {
+            yield();
+        }
+    };
+    println!("{:?}", x);
+}
+
+fn yield_during_iter_borrowed_slice_3() {
+    // OK to take a mutable ref to `x` and yield
+    // up pointers from it:
+    let mut x = vec![22_i32];
+    let mut b = || {
+        for p in &mut x {
+            yield p;
+        }
+    };
+    b.resume();
+}
+
+fn yield_during_iter_borrowed_slice_4() {
+    // ...but not OK to do that while reading
+    // from `x` too
+    let mut x = vec![22_i32];
+    let mut b = || {
+        for p in &mut x {
+            yield p;
+        }
+    };
+    println!("{}", x[0]); //~ ERROR
+    b.resume();
+}
+
+fn yield_during_range_iter() {
+    // Should be OK.
+    let mut b = || {
+        let v = vec![1,2,3];
+        let len = v.len();
+        for i in 0..len {
+            let x = v[i];
+            yield x;
+        }
+    };
+    b.resume();
+}
+
+fn main() { }
diff --git a/src/test/ui/generator/yield-while-iterating.stderr b/src/test/ui/generator/yield-while-iterating.stderr
new file mode 100644
index 0000000000000..ea55e032e4761
--- /dev/null
+++ b/src/test/ui/generator/yield-while-iterating.stderr
@@ -0,0 +1,24 @@
+error[E0626]: borrow may still be in use when generator yields
+  --> $DIR/yield-while-iterating.rs:22:19
+   |
+22 |         for p in &x { //~ ERROR
+   |                   ^
+23 |             yield();
+   |             ------- possible yield occurs here
+
+error[E0502]: cannot borrow `x` as immutable because it is also borrowed as mutable
+  --> $DIR/yield-while-iterating.rs:67:20
+   |
+62 |     let mut b = || {
+   |                 -- mutable borrow occurs here
+63 |         for p in &mut x {
+   |                       - previous borrow occurs due to use of `x` in closure
+...
+67 |     println!("{}", x[0]); //~ ERROR
+   |                    ^ immutable borrow occurs here
+68 |     b.resume();
+69 | }
+   | - mutable borrow ends here
+
+error: aborting due to 2 previous errors
+
diff --git a/src/test/ui/generator/yield-while-local-borrowed.rs b/src/test/ui/generator/yield-while-local-borrowed.rs
new file mode 100644
index 0000000000000..d21c86e88681e
--- /dev/null
+++ b/src/test/ui/generator/yield-while-local-borrowed.rs
@@ -0,0 +1,56 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(generators, generator_trait)]
+
+use std::ops::{GeneratorState, Generator};
+use std::cell::Cell;
+
+fn borrow_local_inline() {
+    // Not OK to yield with a borrow of a temporary.
+    //
+    // (This error occurs because the region shows up in the type of
+    // `b` and gets extended by region inference.)
+    let mut b = move || {
+        let a = &3; //~ ERROR
+        yield();
+        println!("{}", a);
+    };
+    b.resume();
+}
+
+fn borrow_local_inline_done() {
+    // No error here -- `a` is not in scope at the point of `yield`.
+    let mut b = move || {
+        {
+            let a = &3;
+        }
+        yield();
+    };
+    b.resume();
+}
+
+fn borrow_local() {
+    // Not OK to yield with a borrow of a temporary.
+    //
+    // (This error occurs because the region shows up in the type of
+    // `b` and gets extended by region inference.)
+    let mut b = move || {
+        let a = 3;
+        {
+            let b = &a; //~ ERROR
+            yield();
+            println!("{}", b);
+        }
+    };
+    b.resume();
+}
+
+fn main() { }
diff --git a/src/test/ui/generator/yield-while-local-borrowed.stderr b/src/test/ui/generator/yield-while-local-borrowed.stderr
new file mode 100644
index 0000000000000..2fe6c686ce366
--- /dev/null
+++ b/src/test/ui/generator/yield-while-local-borrowed.stderr
@@ -0,0 +1,10 @@
+error[E0626]: borrow may still be in use when generator yields
+  --> $DIR/yield-while-local-borrowed.rs:48:22
+   |
+48 |             let b = &a; //~ ERROR
+   |                      ^
+49 |             yield();
+   |             ------- possible yield occurs here
+
+error: aborting due to previous error
+
diff --git a/src/test/ui/generator/yield-while-ref-reborrowed.rs b/src/test/ui/generator/yield-while-ref-reborrowed.rs
new file mode 100644
index 0000000000000..b9c963ae74077
--- /dev/null
+++ b/src/test/ui/generator/yield-while-ref-reborrowed.rs
@@ -0,0 +1,49 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(generators, generator_trait)]
+
+use std::ops::{GeneratorState, Generator};
+use std::cell::Cell;
+
+fn reborrow_shared_ref(x: &i32) {
+    // This is OK -- we have a borrow live over the yield, but it's of
+    // data that outlives the generator.
+    let mut b = move || {
+        let a = &*x;
+        yield();
+        println!("{}", a);
+    };
+    b.resume();
+}
+
+fn reborrow_mutable_ref(x: &mut i32) {
+    // This is OK -- we have a borrow live over the yield, but it's of
+    // data that outlives the generator.
+    let mut b = move || {
+        let a = &mut *x;
+        yield();
+        println!("{}", a);
+    };
+    b.resume();
+}
+
+fn reborrow_mutable_ref_2(x: &mut i32) {
+    // ...but not OK to go on using `x`.
+    let mut b = || {
+        let a = &mut *x;
+        yield();
+        println!("{}", a);
+    };
+    println!("{}", x); //~ ERROR
+    b.resume();
+}
+
+fn main() { }
diff --git a/src/test/ui/generator/yield-while-ref-reborrowed.stderr b/src/test/ui/generator/yield-while-ref-reborrowed.stderr
new file mode 100644
index 0000000000000..7269f72973701
--- /dev/null
+++ b/src/test/ui/generator/yield-while-ref-reborrowed.stderr
@@ -0,0 +1,16 @@
+error[E0501]: cannot borrow `x` as immutable because previous closure requires unique access
+  --> $DIR/yield-while-ref-reborrowed.rs:45:20
+   |
+40 |     let mut b = || {
+   |                 -- closure construction occurs here
+41 |         let a = &mut *x;
+   |                       - previous borrow occurs due to use of `x` in closure
+...
+45 |     println!("{}", x); //~ ERROR
+   |                    ^ borrow occurs here
+46 |     b.resume();
+47 | }
+   | - borrow from closure ends here
+
+error: aborting due to previous error
+
diff --git a/src/test/ui/impl-trait/no-method-suggested-traits.stderr b/src/test/ui/impl-trait/no-method-suggested-traits.stderr
index fc441f9484273..23f115858cd5e 100644
--- a/src/test/ui/impl-trait/no-method-suggested-traits.stderr
+++ b/src/test/ui/impl-trait/no-method-suggested-traits.stderr
@@ -8,6 +8,8 @@ error[E0599]: no method named `method` found for type `u32` in the current scope
    = note: the following traits are implemented but not in scope, perhaps add a `use` for one of them:
            candidate #1: `use foo::Bar;`
            candidate #2: `use no_method_suggested_traits::foo::PubPub;`
+           candidate #3: `use no_method_suggested_traits::qux::PrivPub;`
+           candidate #4: `use no_method_suggested_traits::Reexported;`
 
 error[E0599]: no method named `method` found for type `std::rc::Rc<&mut std::boxed::Box<&u32>>` in the current scope
   --> $DIR/no-method-suggested-traits.rs:38:44
@@ -19,6 +21,8 @@ error[E0599]: no method named `method` found for type `std::rc::Rc<&mut std::box
    = note: the following traits are implemented but not in scope, perhaps add a `use` for one of them:
            candidate #1: `use foo::Bar;`
            candidate #2: `use no_method_suggested_traits::foo::PubPub;`
+           candidate #3: `use no_method_suggested_traits::qux::PrivPub;`
+           candidate #4: `use no_method_suggested_traits::Reexported;`
 
 error[E0599]: no method named `method` found for type `char` in the current scope
   --> $DIR/no-method-suggested-traits.rs:44:9
diff --git a/src/test/ui/lint/not_found.rs b/src/test/ui/lint/not_found.rs
new file mode 100644
index 0000000000000..5cdc19823cfff
--- /dev/null
+++ b/src/test/ui/lint/not_found.rs
@@ -0,0 +1,21 @@
+// Copyright 2014–2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// this tests the `unknown_lint` lint, especially the suggestions
+
+// the suggestion only appears if a lint with the lowercase name exists
+#[allow(FOO_BAR)]
+// the suggestion appears on all-uppercase names
+#[warn(DEAD_CODE)]
+// the suggestion appears also on mixed-case names
+#[deny(Warnings)]
+fn main() {
+    unimplemented!();
+}
diff --git a/src/test/ui/lint/not_found.stderr b/src/test/ui/lint/not_found.stderr
new file mode 100644
index 0000000000000..73265845494c2
--- /dev/null
+++ b/src/test/ui/lint/not_found.stderr
@@ -0,0 +1,20 @@
+warning: unknown lint: `FOO_BAR`
+  --> $DIR/not_found.rs:14:9
+   |
+14 | #[allow(FOO_BAR)]
+   |         ^^^^^^^
+   |
+   = note: #[warn(unknown_lints)] on by default
+
+warning: unknown lint: `DEAD_CODE`
+  --> $DIR/not_found.rs:16:8
+   |
+16 | #[warn(DEAD_CODE)]
+   |        ^^^^^^^^^ help: lowercase the lint name: `dead_code`
+
+warning: unknown lint: `Warnings`
+  --> $DIR/not_found.rs:18:8
+   |
+18 | #[deny(Warnings)]
+   |        ^^^^^^^^ help: lowercase the lint name: `warnings`
+
diff --git a/src/test/ui/mismatched_types/closure-mismatch.stderr b/src/test/ui/mismatched_types/closure-mismatch.stderr
index b7479f15b1812..d928a6a0a8e64 100644
--- a/src/test/ui/mismatched_types/closure-mismatch.stderr
+++ b/src/test/ui/mismatched_types/closure-mismatch.stderr
@@ -4,7 +4,6 @@ error[E0271]: type mismatch resolving `for<'r> <[closure@$DIR/closure-mismatch.r
 18 |     baz(|_| ());
    |     ^^^ expected bound lifetime parameter, found concrete lifetime
    |
-   = note: concrete lifetime that was found is lifetime '_#0r
    = note: required because of the requirements on the impl of `Foo` for `[closure@$DIR/closure-mismatch.rs:18:9: 18:15]`
    = note: required by `baz`
 
diff --git a/src/test/ui/mismatched_types/issue-36053-2.stderr b/src/test/ui/mismatched_types/issue-36053-2.stderr
index 174f7dfa0d0f5..e2e2019307f34 100644
--- a/src/test/ui/mismatched_types/issue-36053-2.stderr
+++ b/src/test/ui/mismatched_types/issue-36053-2.stderr
@@ -5,8 +5,8 @@ error[E0599]: no method named `count` found for type `std::iter::Filter<std::ite
    |                                                       ^^^^^
    |
    = note: the method `count` exists but the following trait bounds were not satisfied:
-           `[closure@$DIR/issue-36053-2.rs:17:39: 17:53] : std::ops::FnMut<(&_,)>`
            `std::iter::Filter<std::iter::Fuse<std::iter::Once<&str>>, [closure@$DIR/issue-36053-2.rs:17:39: 17:53]> : std::iter::Iterator`
+           `&mut std::iter::Filter<std::iter::Fuse<std::iter::Once<&str>>, [closure@$DIR/issue-36053-2.rs:17:39: 17:53]> : std::iter::Iterator`
 
 error[E0281]: type mismatch: `[closure@$DIR/issue-36053-2.rs:17:39: 17:53]` implements the trait `for<'r> std::ops::FnMut<(&'r str,)>`, but the trait `for<'r> std::ops::FnMut<(&'r &str,)>` is required
   --> $DIR/issue-36053-2.rs:17:32
diff --git a/src/test/ui/on-unimplemented/bad-annotation.rs b/src/test/ui/on-unimplemented/bad-annotation.rs
index 8580749084d22..54d3b3e087653 100644
--- a/src/test/ui/on-unimplemented/bad-annotation.rs
+++ b/src/test/ui/on-unimplemented/bad-annotation.rs
@@ -37,5 +37,29 @@ trait BadAnnotation2<A,B>
 trait BadAnnotation3<A,B>
 {}
 
+#[rustc_on_unimplemented(lorem="")]
+trait BadAnnotation4 {}
+
+#[rustc_on_unimplemented(lorem(ipsum(dolor)))]
+trait BadAnnotation5 {}
+
+#[rustc_on_unimplemented(message="x", message="y")]
+trait BadAnnotation6 {}
+
+#[rustc_on_unimplemented(message="x", on(desugared, message="y"))]
+trait BadAnnotation7 {}
+
+#[rustc_on_unimplemented(on(), message="y")]
+trait BadAnnotation8 {}
+
+#[rustc_on_unimplemented(on="x", message="y")]
+trait BadAnnotation9 {}
+
+#[rustc_on_unimplemented(on(x="y"), message="y")]
+trait BadAnnotation10 {}
+
+#[rustc_on_unimplemented(on(desugared, on(desugared, message="x")), message="y")]
+trait BadAnnotation11 {}
+
 pub fn main() {
 }
diff --git a/src/test/ui/on-unimplemented/bad-annotation.stderr b/src/test/ui/on-unimplemented/bad-annotation.stderr
index 8599477e8ed7e..73834f4422d38 100644
--- a/src/test/ui/on-unimplemented/bad-annotation.stderr
+++ b/src/test/ui/on-unimplemented/bad-annotation.stderr
@@ -1,8 +1,8 @@
-error[E0232]: this attribute must have a value
+error[E0232]: `#[rustc_on_unimplemented]` requires a value
   --> $DIR/bad-annotation.rs:26:1
    |
 26 | #[rustc_on_unimplemented] //~ ERROR this attribute must have a value
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^ attribute requires a value
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^ value required here
    |
    = note: eg `#[rustc_on_unimplemented = "foo"]`
 
@@ -18,5 +18,59 @@ error[E0231]: only named substitution parameters are allowed
 35 | #[rustc_on_unimplemented = "Unimplemented trait error on `{Self}` with params `<{A},{B},{}>`"]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 3 previous errors
+error[E0232]: this attribute must have a valid value
+  --> $DIR/bad-annotation.rs:40:26
+   |
+40 | #[rustc_on_unimplemented(lorem="")]
+   |                          ^^^^^^^^ expected value here
+   |
+   = note: eg `#[rustc_on_unimplemented = "foo"]`
+
+error[E0232]: this attribute must have a valid value
+  --> $DIR/bad-annotation.rs:43:26
+   |
+43 | #[rustc_on_unimplemented(lorem(ipsum(dolor)))]
+   |                          ^^^^^^^^^^^^^^^^^^^ expected value here
+   |
+   = note: eg `#[rustc_on_unimplemented = "foo"]`
+
+error[E0232]: this attribute must have a valid value
+  --> $DIR/bad-annotation.rs:46:39
+   |
+46 | #[rustc_on_unimplemented(message="x", message="y")]
+   |                                       ^^^^^^^^^^^ expected value here
+   |
+   = note: eg `#[rustc_on_unimplemented = "foo"]`
+
+error[E0232]: this attribute must have a valid value
+  --> $DIR/bad-annotation.rs:49:39
+   |
+49 | #[rustc_on_unimplemented(message="x", on(desugared, message="y"))]
+   |                                       ^^^^^^^^^^^^^^^^^^^^^^^^^^ expected value here
+   |
+   = note: eg `#[rustc_on_unimplemented = "foo"]`
+
+error[E0232]: empty `on`-clause in `#[rustc_on_unimplemented]`
+  --> $DIR/bad-annotation.rs:52:26
+   |
+52 | #[rustc_on_unimplemented(on(), message="y")]
+   |                          ^^^^ empty on-clause here
+
+error[E0232]: this attribute must have a valid value
+  --> $DIR/bad-annotation.rs:55:26
+   |
+55 | #[rustc_on_unimplemented(on="x", message="y")]
+   |                          ^^^^^^ expected value here
+   |
+   = note: eg `#[rustc_on_unimplemented = "foo"]`
+
+error[E0232]: this attribute must have a valid value
+  --> $DIR/bad-annotation.rs:61:40
+   |
+61 | #[rustc_on_unimplemented(on(desugared, on(desugared, message="x")), message="y")]
+   |                                        ^^^^^^^^^^^^^^^^^^^^^^^^^^ expected value here
+   |
+   = note: eg `#[rustc_on_unimplemented = "foo"]`
+
+error: aborting due to 10 previous errors
 
diff --git a/src/test/ui/resolve/token-error-correct.stderr b/src/test/ui/resolve/token-error-correct.stderr
index 226fa6469bc74..281c21f6f85ee 100644
--- a/src/test/ui/resolve/token-error-correct.stderr
+++ b/src/test/ui/resolve/token-error-correct.stderr
@@ -28,11 +28,11 @@ error: expected expression, found `;`
 14 |     foo(bar(;
    |             ^
 
-error: expected one of `)`, `,`, `.`, `<`, `?`, `break`, `continue`, `false`, `for`, `if`, `loop`, `match`, `move`, `return`, `true`, `unsafe`, `while`, or an operator, found `;`
+error: expected one of `)`, `,`, `.`, `<`, `?`, `break`, `continue`, `false`, `for`, `if`, `loop`, `match`, `move`, `return`, `true`, `unsafe`, `while`, `yield`, or an operator, found `;`
   --> $DIR/token-error-correct.rs:14:13
    |
 14 |     foo(bar(;
-   |             ^ expected one of 18 possible tokens here
+   |             ^ expected one of 19 possible tokens here
 
 error: expected expression, found `)`
   --> $DIR/token-error-correct.rs:23:1
diff --git a/src/test/ui/span/gated-features-attr-spans.rs b/src/test/ui/span/gated-features-attr-spans.rs
new file mode 100644
index 0000000000000..d5ccd2ea7ad3f
--- /dev/null
+++ b/src/test/ui/span/gated-features-attr-spans.rs
@@ -0,0 +1,39 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(attr_literals)]
+
+#[repr(align(16))]
+struct Gem {
+    mohs_hardness: u8,
+    poofed: bool,
+    weapon: Weapon,
+}
+
+#[repr(simd)]
+struct Weapon {
+    name: String,
+    damage: u32
+}
+
+impl Gem {
+    #[must_use] fn summon_weapon(&self) -> Weapon { self.weapon }
+}
+
+#[must_use]
+fn bubble(gem: Gem) -> Result<Gem, ()> {
+    if gem.poofed {
+        Ok(gem)
+    } else {
+        Err(())
+    }
+}
+
+fn main() {}
diff --git a/src/test/ui/span/gated-features-attr-spans.stderr b/src/test/ui/span/gated-features-attr-spans.stderr
new file mode 100644
index 0000000000000..66b2567f728a3
--- /dev/null
+++ b/src/test/ui/span/gated-features-attr-spans.stderr
@@ -0,0 +1,34 @@
+error: the struct `#[repr(align(u16))]` attribute is experimental (see issue #33626)
+  --> $DIR/gated-features-attr-spans.rs:13:1
+   |
+13 | #[repr(align(16))]
+   | ^^^^^^^^^^^^^^^^^^
+   |
+   = help: add #![feature(repr_align)] to the crate attributes to enable
+
+error: SIMD types are experimental and possibly buggy (see issue #27731)
+  --> $DIR/gated-features-attr-spans.rs:20:1
+   |
+20 | #[repr(simd)]
+   | ^^^^^^^^^^^^^
+   |
+   = help: add #![feature(repr_simd)] to the crate attributes to enable
+
+warning: `#[must_use]` on methods is experimental (see issue #43302)
+  --> $DIR/gated-features-attr-spans.rs:27:5
+   |
+27 |     #[must_use] fn summon_weapon(&self) -> Weapon { self.weapon }
+   |     ^^^^^^^^^^^
+   |
+   = help: add #![feature(fn_must_use)] to the crate attributes to enable
+
+warning: `#[must_use]` on functions is experimental (see issue #43302)
+  --> $DIR/gated-features-attr-spans.rs:30:1
+   |
+30 | #[must_use]
+   | ^^^^^^^^^^^
+   |
+   = help: add #![feature(fn_must_use)] to the crate attributes to enable
+
+error: aborting due to 2 previous errors
+
diff --git a/src/test/ui/span/lint-unused-unsafe.stderr b/src/test/ui/span/lint-unused-unsafe.stderr
index f4998e08907a3..1fa5f94aa4ca6 100644
--- a/src/test/ui/span/lint-unused-unsafe.stderr
+++ b/src/test/ui/span/lint-unused-unsafe.stderr
@@ -65,14 +65,12 @@ note: because it's nested under this `unsafe` block
    | |_____^
 
 error: unnecessary `unsafe` block
-  --> $DIR/lint-unused-unsafe.rs:39:5
+  --> $DIR/lint-unused-unsafe.rs:40:9
    |
-39 | /     unsafe {                             //~ ERROR: unnecessary `unsafe` block
-40 | |         unsafe {                         //~ ERROR: unnecessary `unsafe` block
+40 | /         unsafe {                         //~ ERROR: unnecessary `unsafe` block
 41 | |             unsf()
 42 | |         }
-43 | |     }
-   | |_____^ unnecessary `unsafe` block
+   | |_________^ unnecessary `unsafe` block
    |
 note: because it's nested under this `unsafe` fn
   --> $DIR/lint-unused-unsafe.rs:38:1
@@ -87,12 +85,14 @@ note: because it's nested under this `unsafe` fn
    | |_^
 
 error: unnecessary `unsafe` block
-  --> $DIR/lint-unused-unsafe.rs:40:9
+  --> $DIR/lint-unused-unsafe.rs:39:5
    |
-40 | /         unsafe {                         //~ ERROR: unnecessary `unsafe` block
+39 | /     unsafe {                             //~ ERROR: unnecessary `unsafe` block
+40 | |         unsafe {                         //~ ERROR: unnecessary `unsafe` block
 41 | |             unsf()
 42 | |         }
-   | |_________^ unnecessary `unsafe` block
+43 | |     }
+   | |_____^ unnecessary `unsafe` block
    |
 note: because it's nested under this `unsafe` fn
   --> $DIR/lint-unused-unsafe.rs:38:1
diff --git a/src/test/ui/span/missing-unit-argument.rs b/src/test/ui/span/missing-unit-argument.rs
new file mode 100644
index 0000000000000..2cdab5bedc49a
--- /dev/null
+++ b/src/test/ui/span/missing-unit-argument.rs
@@ -0,0 +1,19 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+fn foo(():(), ():()) {}
+fn bar(():()) {}
+
+fn main() {
+    let _: Result<(), String> = Ok();
+    foo();
+    foo(());
+    bar();
+}
diff --git a/src/test/ui/span/missing-unit-argument.stderr b/src/test/ui/span/missing-unit-argument.stderr
new file mode 100644
index 0000000000000..e508a30d1826c
--- /dev/null
+++ b/src/test/ui/span/missing-unit-argument.stderr
@@ -0,0 +1,45 @@
+error[E0061]: this function takes 1 parameter but 0 parameters were supplied
+  --> $DIR/missing-unit-argument.rs:15:33
+   |
+15 |     let _: Result<(), String> = Ok();
+   |                                 ^^^^
+   |
+help: expected the unit value `()`. You can create one with a pair of parenthesis
+   |
+15 |     let _: Result<(), String> = Ok(());
+   |                                    ^^
+
+error[E0061]: this function takes 2 parameters but 0 parameters were supplied
+  --> $DIR/missing-unit-argument.rs:16:5
+   |
+11 | fn foo(():(), ():()) {}
+   | ----------------------- defined here
+...
+16 |     foo();
+   |     ^^^^^ expected 2 parameters
+
+error[E0061]: this function takes 2 parameters but 1 parameter was supplied
+  --> $DIR/missing-unit-argument.rs:17:9
+   |
+11 | fn foo(():(), ():()) {}
+   | ----------------------- defined here
+...
+17 |     foo(());
+   |         ^^ expected 2 parameters
+
+error[E0061]: this function takes 1 parameter but 0 parameters were supplied
+  --> $DIR/missing-unit-argument.rs:18:5
+   |
+12 | fn bar(():()) {}
+   | ---------------- defined here
+...
+18 |     bar();
+   |     ^^^^^
+   |
+help: expected the unit value `()`. You can create one with a pair of parenthesis
+   |
+18 |     bar(());
+   |         ^^
+
+error: aborting due to 4 previous errors
+
diff --git a/src/test/ui/suggestions/issue-43420-no-over-suggest.rs b/src/test/ui/suggestions/issue-43420-no-over-suggest.rs
new file mode 100644
index 0000000000000..d504b7cae28c4
--- /dev/null
+++ b/src/test/ui/suggestions/issue-43420-no-over-suggest.rs
@@ -0,0 +1,19 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// check that we substitute type parameters before we suggest anything - otherwise
+// we would suggest function such as `as_slice` for the `&[u16]`.
+
+fn foo(b: &[u16]) {}
+
+fn main() {
+    let a: Vec<u8> = Vec::new();
+    foo(&a);
+}
diff --git a/src/test/ui/suggestions/issue-43420-no-over-suggest.stderr b/src/test/ui/suggestions/issue-43420-no-over-suggest.stderr
new file mode 100644
index 0000000000000..bcad9ce56c65e
--- /dev/null
+++ b/src/test/ui/suggestions/issue-43420-no-over-suggest.stderr
@@ -0,0 +1,11 @@
+error[E0308]: mismatched types
+  --> $DIR/issue-43420-no-over-suggest.rs:18:9
+   |
+18 |     foo(&a);
+   |         ^^ expected slice, found struct `std::vec::Vec`
+   |
+   = note: expected type `&[u16]`
+              found type `&std::vec::Vec<u8>`
+
+error: aborting due to previous error
+
diff --git a/src/test/ui/suggestions/try-operator-on-main.rs b/src/test/ui/suggestions/try-operator-on-main.rs
index 55154e3507e87..eadd12924df66 100644
--- a/src/test/ui/suggestions/try-operator-on-main.rs
+++ b/src/test/ui/suggestions/try-operator-on-main.rs
@@ -8,6 +8,26 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+#![feature(try_trait)]
+
+use std::ops::Try;
+
 fn main() {
+    // error for a `Try` type on a non-`Try` fn
     std::fs::File::open("foo")?;
+
+    // a non-`Try` type on a non-`Try` fn
+    ()?;
+
+    // an unrelated use of `Try`
+    try_trait_generic::<()>();
+}
+
+
+
+fn try_trait_generic<T: Try>() -> T {
+    // and a non-`Try` object on a `Try` fn.
+    ()?;
+
+    loop {}
 }
diff --git a/src/test/ui/suggestions/try-operator-on-main.stderr b/src/test/ui/suggestions/try-operator-on-main.stderr
index cf0481bdab772..e83bf2abc1504 100644
--- a/src/test/ui/suggestions/try-operator-on-main.stderr
+++ b/src/test/ui/suggestions/try-operator-on-main.stderr
@@ -1,14 +1,46 @@
-error[E0277]: the trait bound `(): std::ops::Try` is not satisfied
-  --> $DIR/try-operator-on-main.rs:12:5
+error[E0277]: the `?` operator can only be used in a function that returns `Result` (or another type that implements `std::ops::Try`)
+  --> $DIR/try-operator-on-main.rs:17:5
    |
-12 |     std::fs::File::open("foo")?;
+17 |     std::fs::File::open("foo")?;
    |     ---------------------------
    |     |
-   |     the `?` operator can only be used in a function that returns `Result` (or another type that implements `std::ops::Try`)
+   |     cannot use the `?` operator in a function that returns `()`
    |     in this macro invocation
    |
    = help: the trait `std::ops::Try` is not implemented for `()`
    = note: required by `std::ops::Try::from_error`
 
-error: aborting due to previous error
+error[E0277]: the `?` operator can only be applied to values that implement `std::ops::Try`
+  --> $DIR/try-operator-on-main.rs:20:5
+   |
+20 |     ()?;
+   |     ---
+   |     |
+   |     the `?` operator cannot be applied to type `()`
+   |     in this macro invocation
+   |
+   = help: the trait `std::ops::Try` is not implemented for `()`
+   = note: required by `std::ops::Try::into_result`
+
+error[E0277]: the trait bound `(): std::ops::Try` is not satisfied
+  --> $DIR/try-operator-on-main.rs:23:5
+   |
+23 |     try_trait_generic::<()>();
+   |     ^^^^^^^^^^^^^^^^^^^^^^^ the trait `std::ops::Try` is not implemented for `()`
+   |
+   = note: required by `try_trait_generic`
+
+error[E0277]: the `?` operator can only be applied to values that implement `std::ops::Try`
+  --> $DIR/try-operator-on-main.rs:30:5
+   |
+30 |     ()?;
+   |     ---
+   |     |
+   |     the `?` operator cannot be applied to type `()`
+   |     in this macro invocation
+   |
+   = help: the trait `std::ops::Try` is not implemented for `()`
+   = note: required by `std::ops::Try::into_result`
+
+error: aborting due to 4 previous errors
 
diff --git a/src/tools/build-manifest/src/main.rs b/src/tools/build-manifest/src/main.rs
index 7a09ae48b91bd..e2be021e7cc39 100644
--- a/src/tools/build-manifest/src/main.rs
+++ b/src/tools/build-manifest/src/main.rs
@@ -239,7 +239,12 @@ impl Builder {
         self.package("rust-std", &mut manifest.pkg, TARGETS);
         self.package("rust-docs", &mut manifest.pkg, TARGETS);
         self.package("rust-src", &mut manifest.pkg, &["*"]);
-        self.package("rls", &mut manifest.pkg, HOSTS);
+        let rls_package_name = if self.rust_release == "nightly" {
+            "rls"
+        } else {
+            "rls-preview"
+        };
+        self.package(rls_package_name, &mut manifest.pkg, HOSTS);
         self.package("rust-analysis", &mut manifest.pkg, TARGETS);
 
         let mut pkg = Package {
@@ -276,7 +281,7 @@ impl Builder {
             }
 
             extensions.push(Component {
-                pkg: "rls".to_string(),
+                pkg: rls_package_name.to_string(),
                 target: host.to_string(),
             });
             extensions.push(Component {
@@ -353,7 +358,7 @@ impl Builder {
             format!("rust-src-{}.tar.gz", self.rust_release)
         } else if component == "cargo" {
             format!("cargo-{}-{}.tar.gz", self.cargo_release, target)
-        } else if component == "rls" {
+        } else if component == "rls" || component == "rls-preview" {
             format!("rls-{}-{}.tar.gz", self.rls_release, target)
         } else {
             format!("{}-{}-{}.tar.gz", component, self.rust_release, target)
@@ -363,7 +368,7 @@ impl Builder {
     fn cached_version(&self, component: &str) -> &str {
         if component == "cargo" {
             &self.cargo_version
-        } else if component == "rls" {
+        } else if component == "rls" || component == "rls-preview" {
             &self.rls_version
         } else {
             &self.rust_version
diff --git a/src/tools/cargo b/src/tools/cargo
index 3d3f2c05d742e..34c0674a25128 160000
--- a/src/tools/cargo
+++ b/src/tools/cargo
@@ -1 +1 @@
-Subproject commit 3d3f2c05d742e5f907e951aa8849b03f0bc1a895
+Subproject commit 34c0674a251287c94cdd1a112966bcb9010c62e8
diff --git a/src/tools/clippy b/src/tools/clippy
new file mode 160000
index 0000000000000..25444585592f5
--- /dev/null
+++ b/src/tools/clippy
@@ -0,0 +1 @@
+Subproject commit 25444585592f5da648edd5317fcdd21f2db8bb64
diff --git a/src/tools/compiletest/src/common.rs b/src/tools/compiletest/src/common.rs
index 0d6b350a1d431..cee7e52c7f3c6 100644
--- a/src/tools/compiletest/src/common.rs
+++ b/src/tools/compiletest/src/common.rs
@@ -83,117 +83,117 @@ impl fmt::Display for Mode {
 
 #[derive(Clone)]
 pub struct Config {
-    // The library paths required for running the compiler
+    /// The library paths required for running the compiler
     pub compile_lib_path: PathBuf,
 
-    // The library paths required for running compiled programs
+    /// The library paths required for running compiled programs
     pub run_lib_path: PathBuf,
 
-    // The rustc executable
+    /// The rustc executable
     pub rustc_path: PathBuf,
 
-    // The rustdoc executable
+    /// The rustdoc executable
     pub rustdoc_path: Option<PathBuf>,
 
-    // The python executable to use for LLDB
+    /// The python executable to use for LLDB
     pub lldb_python: String,
 
-    // The python executable to use for htmldocck
+    /// The python executable to use for htmldocck
     pub docck_python: String,
 
-    // The llvm FileCheck binary path
+    /// The llvm FileCheck binary path
     pub llvm_filecheck: Option<PathBuf>,
 
-    // The valgrind path
+    /// The valgrind path
     pub valgrind_path: Option<String>,
 
-    // Whether to fail if we can't run run-pass-valgrind tests under valgrind
-    // (or, alternatively, to silently run them like regular run-pass tests).
+    /// Whether to fail if we can't run run-pass-valgrind tests under valgrind
+    /// (or, alternatively, to silently run them like regular run-pass tests).
     pub force_valgrind: bool,
 
-    // The directory containing the tests to run
+    /// The directory containing the tests to run
     pub src_base: PathBuf,
 
-    // The directory where programs should be built
+    /// The directory where programs should be built
     pub build_base: PathBuf,
 
-    // The name of the stage being built (stage1, etc)
+    /// The name of the stage being built (stage1, etc)
     pub stage_id: String,
 
-    // The test mode, compile-fail, run-fail, run-pass
+    /// The test mode, compile-fail, run-fail, run-pass
     pub mode: Mode,
 
-    // Run ignored tests
+    /// Run ignored tests
     pub run_ignored: bool,
 
-    // Only run tests that match this filter
+    /// Only run tests that match this filter
     pub filter: Option<String>,
 
-    // Exactly match the filter, rather than a substring
+    /// Exactly match the filter, rather than a substring
     pub filter_exact: bool,
 
-    // Write out a parseable log of tests that were run
+    /// Write out a parseable log of tests that were run
     pub logfile: Option<PathBuf>,
 
-    // A command line to prefix program execution with,
-    // for running under valgrind
+    /// A command line to prefix program execution with,
+    /// for running under valgrind
     pub runtool: Option<String>,
 
-    // Flags to pass to the compiler when building for the host
+    /// Flags to pass to the compiler when building for the host
     pub host_rustcflags: Option<String>,
 
-    // Flags to pass to the compiler when building for the target
+    /// Flags to pass to the compiler when building for the target
     pub target_rustcflags: Option<String>,
 
-    // Target system to be tested
+    /// Target system to be tested
     pub target: String,
 
-    // Host triple for the compiler being invoked
+    /// Host triple for the compiler being invoked
     pub host: String,
 
-    // Path to / name of the GDB executable
+    /// Path to / name of the GDB executable
     pub gdb: Option<String>,
 
-    // Version of GDB, encoded as ((major * 1000) + minor) * 1000 + patch
+    /// Version of GDB, encoded as ((major * 1000) + minor) * 1000 + patch
     pub gdb_version: Option<u32>,
 
-    // Whether GDB has native rust support
+    /// Whether GDB has native rust support
     pub gdb_native_rust: bool,
 
-    // Version of LLDB
+    /// Version of LLDB
     pub lldb_version: Option<String>,
 
-    // Version of LLVM
+    /// Version of LLVM
     pub llvm_version: Option<String>,
 
-    // Is LLVM a system LLVM
+    /// Is LLVM a system LLVM
     pub system_llvm: bool,
 
-    // Path to the android tools
+    /// Path to the android tools
     pub android_cross_path: PathBuf,
 
-    // Extra parameter to run adb on arm-linux-androideabi
+    /// Extra parameter to run adb on arm-linux-androideabi
     pub adb_path: String,
 
-    // Extra parameter to run test suite on arm-linux-androideabi
+    /// Extra parameter to run test suite on arm-linux-androideabi
     pub adb_test_dir: String,
 
-    // status whether android device available or not
+    /// status whether android device available or not
     pub adb_device_status: bool,
 
-    // the path containing LLDB's Python module
+    /// the path containing LLDB's Python module
     pub lldb_python_dir: Option<String>,
 
-    // Explain what's going on
+    /// Explain what's going on
     pub verbose: bool,
 
-    // Print one character per test instead of one line
+    /// Print one character per test instead of one line
     pub quiet: bool,
 
-    // Whether to use colors in test.
+    /// Whether to use colors in test.
     pub color: ColorConfig,
 
-    // where to find the remote test client process, if we're using it
+    /// where to find the remote test client process, if we're using it
     pub remote_test_client: Option<PathBuf>,
 
     // Configuration for various run-make tests frobbing things like C compilers
diff --git a/src/tools/rls b/src/tools/rls
index 25ffb3a3d7809..303671ea8103c 160000
--- a/src/tools/rls
+++ b/src/tools/rls
@@ -1 +1 @@
-Subproject commit 25ffb3a3d7809b4fa112f3e04e926eb539dd5e90
+Subproject commit 303671ea8103cbc39575a1f47a204159546a04d0
diff --git a/src/tools/tidy/src/deps.rs b/src/tools/tidy/src/deps.rs
index f572ad9cd0204..e9e4b55402c47 100644
--- a/src/tools/tidy/src/deps.rs
+++ b/src/tools/tidy/src/deps.rs
@@ -33,6 +33,12 @@ static EXCEPTIONS: &'static [&'static str] = &[
     "openssl", // BSD+advertising clause, cargo, mdbook
     "pest", // MPL2, mdbook via handlebars
     "thread-id", // Apache-2.0, mdbook
+    "cssparser", // MPL-2.0, rustdoc
+    "smallvec", // MPL-2.0, rustdoc
+    "magenta-sys", // BSD-3-Clause, rustdoc
+    "magenta", // BSD-3-Clause, rustdoc
+    "cssparser-macros", // MPL-2.0, rustdoc
+    "selectors", // MPL-2.0, rustdoc
 ];
 
 pub fn check(path: &Path, bad: &mut bool) {
diff --git a/src/tools/tidy/src/lib.rs b/src/tools/tidy/src/lib.rs
index 020570e61dc63..731a3d96cff9d 100644
--- a/src/tools/tidy/src/lib.rs
+++ b/src/tools/tidy/src/lib.rs
@@ -62,6 +62,7 @@ fn filter_dirs(path: &Path) -> bool {
         "src/rt/hoedown",
         "src/tools/cargo",
         "src/tools/rls",
+        "src/tools/clippy",
         "src/tools/rust-installer",
     ];
     skip.iter().any(|p| path.ends_with(p))
diff --git a/src/tools/tidy/src/pal.rs b/src/tools/tidy/src/pal.rs
index 10c9971382046..8092a9e156beb 100644
--- a/src/tools/tidy/src/pal.rs
+++ b/src/tools/tidy/src/pal.rs
@@ -65,11 +65,10 @@ const EXCEPTION_PATHS: &'static [&'static str] = &[
     "src/rtstartup", // Not sure what to do about this. magic stuff for mingw
 
     // temporary exceptions
-    "src/libstd/rtdeps.rs", // Until rustbuild replaces make
+    "src/libstd/lib.rs", // FIXME(#44217)
     "src/libstd/path.rs",
     "src/libstd/f32.rs",
     "src/libstd/f64.rs",
-    "src/libstd/lib.rs", // Until next stage0 snapshot bump
     "src/libstd/sys_common/mod.rs",
     "src/libstd/sys_common/net.rs",
     "src/libterm", // Not sure how to make this crate portable, but test needs it