Rollup merge of rust-lang#91875 - b-naber:mir-transform-norm-erase-re…

…g, r=Aaron1011

Use try_normalize_erasing_regions in RevealAllVisitor

Fixes rust-lang#91745

Thanks to `@Aaron1011` for [pointing out the problem](rust-lang#91745 (comment)).

r? `@Aaron1011`

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);
     }
 }

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=()> = &();
+}