Bad error message with Self in inner function

[tbu-]

Updated example

trait Trait {
    fn outer(self) {
        fn inner(_: Self) {
        }
    }
}

fn main() { }

error: missing `Self` type param in the substitution of `fn(Self)`

Original issue

I have no idea where this came from, so here's a stacktrace.

Starting program: /usr/bin/rustc datafile_raw.rs
warning: Could not load shared library symbols for linux-vdso.so.1.
Do you need "set solib-search-path" or "set sysroot"?
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/usr/lib/libthread_db.so.1".
warning: File "/usr/lib/libstdc++.so.6.0.19-gdb.py" auto-loading has been declined by your `auto-load safe-path' set to "$debugdir:$datadir/auto-load".
[New Thread 0x7ffff1f78480 (LWP 4681)]
datafile_raw.rs:348:75: 348:81 error: mismatched types: expected `fn(<generic #1>, &&'a Self) -> <generic #2>` but found `fn(uint, &'a Self) -> DatafileItem<'a>` (expected &-ptr but found self)
datafile_raw.rs:348         MapIterator { data: self, iterator: range(0, self.num_items()), map_fn: map_fn }
                                                    ^~~~~~
datafile_raw.rs:348:3: 348:83 error: mismatched types: expected `DatafileItemIterator<'a,Self>` but found `MapIterator<<generic #1>,<generic #2>,&'a Self,std::iter::Range<uint>>` (expected struct DatafileItemIterator but found struct MapIterator)
datafile_raw.rs:348         MapIterator { data: self, iterator: range(0, self.num_items()), map_fn: map_fn }
                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
[Switching to Thread 0x7ffff1f78480 (LWP 4681)]

Breakpoint 1, std::rt::unwind::Unwinder::begin_unwind::rust_fail () at src/libstd/rt/global_heap.rs:71
71  pub unsafe fn exchange_malloc(size: uint) -> *u8 {
(gdb) bt
#0  std::rt::unwind::Unwinder::begin_unwind::rust_fail () at src/libstd/rt/global_heap.rs:71
#1  0x00007ffff775c961 in std::rt::unwind::Unwinder::begin_unwind (self=0x6066a8, cause=...) at src/libstd/rt/unwind.rs:220
#2  0x00007ffff76bfa29 in std::rt::unwind::begin_unwind_inner (msg=..., file=..., line=148) at src/libstd/rt/unwind.rs:538
#3  0x00007ffff371240e in rt::unwind::begin_unwind::h2c1d88c0eb2e464eqik::v0.10.pre () from /usr/lib/librustc-6ccece0c-0.10-pre.so
#4  0x00007ffff3964b1c in lookup_vtable (vcx=<optimized out>, location_info=<optimized out>, trait_ref=<optimized out>, is_early=<optimized out>)
    at src/librustc/middle/typeck/check/vtable.rs:272
#5  push_inherent_candidates_from_self (self=<optimized out>, restrict_to=..., rcvr_ty=...) at src/librustc/middle/typeck/check/method.rs:498
#6  rustc::middle::typeck::check::method::LookupContext<'a>::push_bound_candidates (self=<optimized out>, restrict_to=..., self_ty=...) at src/librustc/middle/typeck/check/method.rs:364
#7  0x00007ffff39625b7 in rustc::middle::typeck::check::method::lookup (fcx=0x7fffecc18a60, expr=<optimized out>, self_expr=<optimized out>, m_name=<optimized out>, deref_args=<optimized out>, 
    check_traits=<optimized out>, autoderef_receiver=<optimized out>, self_ty=..., supplied_tps=...) at src/librustc/middle/typeck/check/method.rs:164
#8  0x00007ffff39a11af in trans_if (fcx=<optimized out>, ast_ty=<optimized out>, expr=<optimized out>, method_name=..., method_name=..., method_name=..., bcx=<optimized out>, 
    if_id=<optimized out>, cond=<optimized out>, thn=<optimized out>, els=..., dest=...) at src/librustc/middle/typeck/check/mod.rs:1921
#9  rustc::middle::typeck::check::check_expr_with_unifier (fcx=0x7fffecc18a60, expr=0x7fffec25f8c0, expected=..., lvalue_pref=<optimized out>, unifier=<optimized out>)
    at src/librustc/middle/typeck/check/mod.rs:2976
#10 0x00007ffff397fae8 in rustc::middle::typeck::check::check_block_with_expected (fcx=0x7fffecc18a60, blk=0x7fffec25f980, expected=...) at src/librustc/middle/typeck/check/mod.rs:1411
#11 0x00007ffff397be11 in rustc::middle::typeck::check::check_fn (ccx=0x7fffec0848c0, body=0x7fffec25f980, fn_kind=Vanilla, inherited=0x7fffecba4c00, purity=<optimized out>, 
    fn_sig=<optimized out>, decl=<optimized out>, id=<optimized out>) at src/librustc/middle/typeck/check/mod.rs:490
#12 0x00007ffff397b6bb in rustc::middle::typeck::check::check_bare_fn (ccx=0x7fffec0848c0, decl=0x7fffec1100b0, body=0x7fffec25f980, id=2447, param_env=..., fty=...)
    at src/librustc/middle/typeck/check/mod.rs:330
#13 0x00007ffff39766da in rustc::middle::typeck::check::check_item (ccx=0x7fffec0848c0, it=<optimized out>) at src/librustc/middle/typeck/check/mod.rs:575
#14 0x00007ffff397a460 in visit::walk_decl::h9cf355b08c4aabd1K1n::v0.10.pre () at src/librustc/middle/typeck/check/mod.rs:311
#15 0x00007ffff397a37e in visit::walk_stmt::h5901a3f261b3e26dy0n::v0.10.pre () at src/librustc/middle/typeck/check/mod.rs:312
#16 0x00007ffff397a113 in visit::walk_block::h45c060989eb1a99ftWn::v0.10.pre () at src/librustc/middle/typeck/check/mod.rs:312
#17 0x00007ffff397abbf in visit::walk_fn::he7254c7311eedc6e1ao::v0.10.pre () at src/librustc/middle/typeck/check/mod.rs:312
#18 0x00007ffff397b238 in visit::walk_method_helper::he88096d2d7de079fQfq::v0.10.pre () at src/librustc/middle/typeck/check/mod.rs:312
#19 0x00007ffff3978625 in visit::walk_item::h0447c6568c46391bN1p::v0.10.pre () at src/librustc/middle/typeck/check/mod.rs:312
#20 0x00007ffff397b4b4 in rustc::middle::typeck::check::check_item_types (ccx=0x7fffec0848c0, krate=<optimized out>) at src/librustc/middle/typeck/check/mod.rs:311
#21 0x00007ffff3a695fc in rustc::util::common::time<(),()> (what=..., do_it=<optimized out>, u=<optimized out>, f=<optimized out>) at src/librustc/util/common.rs:25
#22 0x00007ffff3a684b7 in rustc::middle::typeck::check_crate (tcx=0x7fffec2b1b90, krate=0x7ffff1f763c0, trait_map=...) at src/librustc/middle/typeck/mod.rs:463
#23 0x00007ffff3da21fa in rustc::driver::driver::phase_3_run_analysis_passes (sess=0x7fffec00ad00, krate=0x7ffff1f763c0, ast_map=...) at src/librustc/driver/driver.rs:316
#24 0x00007ffff3daa32f in rustc::driver::driver::compile_input (sess=0x7fffec00ad00, cfg=..., input=<optimized out>, outdir=<optimized out>, output=<optimized out>)
    at src/librustc/driver/driver.rs:573
#25 0x00007ffff3dcefe5 in rustc::run_compiler (args=...) at src/librustc/lib.rs:339
#26 0x00007ffff3ddef5d in fn91262 () at src/librustc/lib.rs:426
#27 0x00007ffff3ddd622 in fn91110 () at src/librustc/lib.rs:388
#28 0x00007ffff3dd958b in task::TaskBuilder::try::closure () at src/librustc/lib.rs:374
#29 0x00007ffff319517c in fn7303 () at src/libnative/task.rs:103
#30 0x00007ffff7756588 in fn42893 () at src/libstd/unstable/finally.rs:45
#31 try_finally<(),(),()> (mutate=<optimized out>, drop=<optimized out>, try_fn=<optimized out>, finally_fn=<optimized out>) at src/libstd/unstable/finally.rs:99
#32 finally (self=0xf000007ffff55187, dtor=<optimized out>) at src/libstd/unstable/finally.rs:44
#33 fn42888 () at src/libstd/rt/task.rs:128
#34 0x00007ffff776031c in rust_try () from /usr/lib/libstd-31b43f22-0.10-pre.so
#35 0x00007ffff77564f1 in std::rt::task::Task::run (self=<optimized out>, f={void (void)} 0x7ffff1f77b98) at src/libstd/rt/local.rs:30
#36 0x00007ffff3195003 in fn7279 () at src/libnative/task.rs:103
#37 0x00007ffff7759d24 in rt::thread::thread_start::h9d943e1fec71bd92kSc::v0.10.pre () at src/libstd/rt/thread.rs:48
#38 0x00007ffff26a30a2 in start_thread () from /usr/lib/libpthread.so.0
#39 0x00007ffff2ea2d1d in clone () from /usr/lib/libc.so.6

[alexcrichton]

Can you provide the code that triggers the assertion as well? Ideally minimized as well, but we can attempt to do that as well.

[tbu-]

Here's a minimized (probably not minimal) non-working example:

use std::iter;

struct Struct {
    data: i32,
}

struct MapIterator<T,U,D,I> {
    data: D,
    iterator: I,
    // `map` is already an function of an iterator, so we can't use `map` as a name here
    map_fn: fn (T, &D) -> U,
}

impl<T,U,D,I:Iterator<T>> Iterator<U> for MapIterator<T,U,D,I> {
    fn next(&mut self) -> Option<U> {
        self.iterator.next().map(|x| (self.map_fn)(x, &self.data))
    }
}

trait Trait {
    fn item(&self, index: uint) -> Struct;
    fn num_items(&self) -> uint;

    fn items<'a>(&'a self) -> MapIterator<uint,Struct,&'a Self,iter::Range<uint>> {
        fn map_fn<'a>(index: uint, df: & &'a Self) -> Struct {
            df.item(index)
        }
        MapIterator { data: self, iterator: range(0, self.num_items()), map_fn: map_fn }
    }
}

fn main() { }

[tbu-]

I'll check whether I can reduce it furtherly.

[tbu-]

use std::iter;

struct MapIterator<T,U,D,I> {
    data: D,
    iterator: I,
    // `map` is already an function of an iterator, so we can't use `map` as a name here
    map_fn: fn (T, &D) -> U,
}

impl<T,U,D,I:Iterator<T>> Iterator<U> for MapIterator<T,U,D,I> {
    fn next(&mut self) -> Option<U> {
        self.iterator.next().map(|x| (self.map_fn)(x, &self.data))
    }
}

trait Trait {
    fn items<'a>(&'a self) -> MapIterator<uint,i32,&'a Self,iter::Range<uint>> {
        fn map_fn<'a>(index: uint, df: & &'a Self) -> i32 {
            0
        }
        MapIterator { data: self, iterator: range(0u, 1), map_fn: map_fn }
    }
}

fn main() { }

When I changed the third type of MapIterator to (), the ICE stopped to appear.

[alexcrichton]

Updating title to ICE message.

[tbu-]

Now it's even shorter:

trait Trait {
    fn outer(self) {
        fn inner(_: Self) {
        }
    }
}

fn main() { }

[lilyball]

I just hit this. Oddly, in my original code, the ICE was actually "Option.unwrap() called on None", but it appears to be the same issue.

[alexcrichton]

Updating, this is no longer an ICE but rather just a pretty bad error message.

[bombless]

error: use of undeclared type name `Self`

The example code still give bad error message above, but the problem is actually a different one today.

[bombless]

BTW, no need to reopen this issue, #24968 already cover the new problem.