Add ICE regression test

Author: flip1995

tests/ui/ice-4545.rs

@@ -0,0 +1,15 @@
+fn repro() {
+    trait Foo {
+        type Bar;
+    }
+
+    #[allow(dead_code)]
+    struct Baz<T: Foo> {
+        field: T::Bar,
+    }
+}
+
+fn main() {
+    repro();
+}
+