normalize the self-type that we extract from impl

Author: nikomatsakis

src/librustc_mir/borrow_check/nll/type_check/mod.rs

@@ -1019,6 +1019,7 @@ impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
                 {
                     let impl_self_ty = tcx.type_of(impl_def_id);
                     let impl_self_ty = impl_self_ty.subst(tcx, &substs);
+                    let impl_self_ty = self.normalize(impl_self_ty, locations);
 
                     // There may be type variables in `substs` and hence
                     // in `impl_self_ty`, but they should all have been

src/test/ui/nll/user-annotations/normalize-self-ty.rs

@@ -0,0 +1,25 @@
+// Regression test for #55183: check a case where the self type from
+// the inherent impl requires normalization to be equal to the
+// user-provided type.
+//
+// run-pass
+
+#![feature(nll)]
+
+trait Mirror {
+    type Me;
+}
+
+impl<T> Mirror for T {
+    type Me = T;
+}
+
+struct Foo<A, B>(A, B);
+
+impl<A> Foo<A, <A as Mirror>::Me> {
+    fn m(b: A) { }
+}
+
+fn main() {
+    <Foo<&'static u32, &u32>>::m(&22);
+}