From 832751fe1df232e36b283fa136b4e26475e55c00 Mon Sep 17 00:00:00 2001
From: Nilstrieb <48135649+Nilstrieb@users.noreply.github.com>
Date: Sat, 28 Jan 2023 20:43:16 +0100
Subject: [PATCH] Also erase substs for new infcx in pin move error

The code originally correctly erased the regions of the type it passed
to the newly created infcx. But after the `fn_sig` query was made to
return an `EarlyBinder<T>`, some substs that were around were
substituted there without erasing their regions. They were then passed
into the newly cerated infcx, which caused the ICE.
---
 .../rustc_borrowck/src/diagnostics/mod.rs     |  4 ++++
 ...-mut-reborrow-infer-var-issue-107419.fixed | 11 ++++++++++
 ...pin-mut-reborrow-infer-var-issue-107419.rs | 11 ++++++++++
 ...mut-reborrow-infer-var-issue-107419.stderr | 20 +++++++++++++++++++
 4 files changed, 46 insertions(+)
 create mode 100644 tests/ui/moves/pin-mut-reborrow-infer-var-issue-107419.fixed
 create mode 100644 tests/ui/moves/pin-mut-reborrow-infer-var-issue-107419.rs
 create mode 100644 tests/ui/moves/pin-mut-reborrow-infer-var-issue-107419.stderr

diff --git a/compiler/rustc_borrowck/src/diagnostics/mod.rs b/compiler/rustc_borrowck/src/diagnostics/mod.rs
index 1011794d7b3b2..8c579bac7e8eb 100644
--- a/compiler/rustc_borrowck/src/diagnostics/mod.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/mod.rs
@@ -1128,8 +1128,12 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                                 "{place_name} {partially_str}moved due to this method call{loop_message}",
                             ),
                         );
+
                         let infcx = tcx.infer_ctxt().build();
+                        // Erase and shadow everything that could be passed to the new infcx.
                         let ty = tcx.erase_regions(moved_place.ty(self.body, tcx).ty);
+                        let method_substs = tcx.erase_regions(method_substs);
+
                         if let ty::Adt(def, substs) = ty.kind()
                             && Some(def.did()) == tcx.lang_items().pin_type()
                             && let ty::Ref(_, _, hir::Mutability::Mut) = substs.type_at(0).kind()
diff --git a/tests/ui/moves/pin-mut-reborrow-infer-var-issue-107419.fixed b/tests/ui/moves/pin-mut-reborrow-infer-var-issue-107419.fixed
new file mode 100644
index 0000000000000..0b9a3bae9619c
--- /dev/null
+++ b/tests/ui/moves/pin-mut-reborrow-infer-var-issue-107419.fixed
@@ -0,0 +1,11 @@
+// run-rustfix
+use std::pin::Pin;
+
+fn foo(_: &mut ()) {}
+
+fn main() {
+    let mut uwu = ();
+    let mut r = Pin::new(&mut uwu);
+    foo(r.as_mut().get_mut());
+    foo(r.get_mut()); //~ ERROR use of moved value
+}
diff --git a/tests/ui/moves/pin-mut-reborrow-infer-var-issue-107419.rs b/tests/ui/moves/pin-mut-reborrow-infer-var-issue-107419.rs
new file mode 100644
index 0000000000000..0e952b06ee118
--- /dev/null
+++ b/tests/ui/moves/pin-mut-reborrow-infer-var-issue-107419.rs
@@ -0,0 +1,11 @@
+// run-rustfix
+use std::pin::Pin;
+
+fn foo(_: &mut ()) {}
+
+fn main() {
+    let mut uwu = ();
+    let mut r = Pin::new(&mut uwu);
+    foo(r.get_mut());
+    foo(r.get_mut()); //~ ERROR use of moved value
+}
diff --git a/tests/ui/moves/pin-mut-reborrow-infer-var-issue-107419.stderr b/tests/ui/moves/pin-mut-reborrow-infer-var-issue-107419.stderr
new file mode 100644
index 0000000000000..7e513b73c21b2
--- /dev/null
+++ b/tests/ui/moves/pin-mut-reborrow-infer-var-issue-107419.stderr
@@ -0,0 +1,20 @@
+error[E0382]: use of moved value: `r`
+  --> $DIR/pin-mut-reborrow-infer-var-issue-107419.rs:10:9
+   |
+LL |     let mut r = Pin::new(&mut uwu);
+   |         ----- move occurs because `r` has type `Pin<&mut ()>`, which does not implement the `Copy` trait
+LL |     foo(r.get_mut());
+   |           --------- `r` moved due to this method call
+LL |     foo(r.get_mut());
+   |         ^ value used here after move
+   |
+note: `Pin::<&'a mut T>::get_mut` takes ownership of the receiver `self`, which moves `r`
+  --> $SRC_DIR/core/src/pin.rs:LL:COL
+help: consider reborrowing the `Pin` instead of moving it
+   |
+LL |     foo(r.as_mut().get_mut());
+   |           +++++++++
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0382`.