test that flip_trait_bound works with trait objects

crates/ide-assists/src/handlers/flip_trait_bound.rs

@@ -58,6 +58,11 @@ fn flip_trait_bound_not_applicable_for_single_trait_bound() {
         check_assist_not_applicable(flip_trait_bound, "struct S<T> where T: $0A { }")
     }
 
+    #[test]
+    fn flip_trait_bound_works_for_dyn() {
+        check_assist(flip_trait_bound, "fn f<'a>(x: dyn Copy $0+ 'a)", "fn f<'a>(x: dyn 'a + Copy)")
+    }
+
     #[test]
     fn flip_trait_bound_works_for_struct() {
         check_assist(