From f3ecd64c617585e79956a3bba265e22ff1cad1e4 Mon Sep 17 00:00:00 2001
From: b-naber <bn263@gmx.de>
Date: Mon, 13 Dec 2021 22:24:08 +0100
Subject: [PATCH] use try_normalize_erasing_regions in RevealAllVisitor

---
 .../rustc_mir_transform/src/reveal_all.rs     |  5 ++++-
 src/test/ui/mir/issue-91745.rs                | 21 +++++++++++++++++++
 2 files changed, 25 insertions(+), 1 deletion(-)
 create mode 100644 src/test/ui/mir/issue-91745.rs

diff --git a/compiler/rustc_mir_transform/src/reveal_all.rs b/compiler/rustc_mir_transform/src/reveal_all.rs
index a717dd3e0cd8a..ee661793a44aa 100644
--- a/compiler/rustc_mir_transform/src/reveal_all.rs
+++ b/compiler/rustc_mir_transform/src/reveal_all.rs
@@ -36,6 +36,9 @@ impl<'tcx> MutVisitor<'tcx> for RevealAllVisitor<'tcx> {
 
     #[inline]
     fn visit_ty(&mut self, ty: &mut Ty<'tcx>, _: TyContext) {
-        *ty = self.tcx.normalize_erasing_regions(self.param_env, ty);
+        // We have to use `try_normalize_erasing_regions` here, since it's
+        // possible that we visit impossible-to-satisfy where clauses here,
+        // see #91745
+        *ty = self.tcx.try_normalize_erasing_regions(self.param_env, *ty).unwrap_or(ty);
     }
 }
diff --git a/src/test/ui/mir/issue-91745.rs b/src/test/ui/mir/issue-91745.rs
new file mode 100644
index 0000000000000..ca3d66b1c8eb7
--- /dev/null
+++ b/src/test/ui/mir/issue-91745.rs
@@ -0,0 +1,21 @@
+// check-pass
+
+pub trait Foo {
+    type Bar;
+}
+
+pub trait Broken {
+    type Assoc;
+    fn broken(&self) where Self::Assoc: Foo;
+}
+
+impl<T> Broken for T {
+    type Assoc = ();
+    fn broken(&self) where Self::Assoc: Foo {
+        let _x: <Self::Assoc as Foo>::Bar;
+    }
+}
+
+fn main() {
+    let _m: &dyn Broken<Assoc=()> = &();
+}