add regression test

tests/ui/layout/rigid-alias-due-to-broken-impl.rs

@@ -0,0 +1,17 @@
+// Make sure we don't ICE if `layout_of` encounters an alias
+// which is rigid due to a malformed program. A regression test
+// for #152545.
+//
+// This specific ICE happens in the `KnownPanicsLint` visitor.
+
+//@ compile-flags: --crate-type=rlib
+trait Foo {
+    type Assoc;
+}
+
+// The trait solver only treats missng associated items
+// as rigid if the self-type is known to be unsized.
+impl Foo for str {}
+//~^ ERROR not all trait items implemented
+
+fn foo(_: [u32; std::mem::size_of::<<str as Foo>::Assoc>()]) {}