Add test for issue-68653

Author: JohnTitor

src/test/ui/generic-associated-types/issue-68653.rs

@@ -0,0 +1,16 @@
+// A regression test for #68653, which was fixed by #68938.
+
+// check-pass
+
+#![allow(incomplete_features)]
+#![feature(generic_associated_types)]
+
+trait Fun {
+    type F<'a: 'a>;
+}
+
+impl <T> Fun for T {
+    type F<'a> = Self;
+}
+
+fn main() {}