Regression test for #63154.

Author: pnkfelix

src/test/ui/nll/issue-63154-normalize.rs

@@ -0,0 +1,34 @@
+// Regression test for rust-lang/rust#63154
+//
+// Before, we would ICE after faiing to normalize the destination type
+// when checking call destinations and also when checking MIR
+// assignment statements.
+
+// check-pass
+
+trait HasAssocType {
+    type Inner;
+}
+
+impl HasAssocType for () {
+    type Inner = ();
+}
+
+trait Tr<I, T>: Fn(I) -> Option<T> {}
+impl<I, T, Q: Fn(I) -> Option<T>> Tr<I, T> for Q {}
+
+fn f<T: HasAssocType>() -> impl Tr<T, T::Inner> {
+    |_| None
+}
+
+fn g<T, Y>(f: impl Tr<T, Y>) -> impl Tr<T, Y> {
+    f
+}
+
+fn h() {
+    g(f())(());
+}
+
+fn main() {
+    h();
+}