error[E0277]: the trait bound `String: MyTrait` is not satisfied
 --> tests/compile_fail/supertraits_are_actually_included.rs:6:6
  |
6 | impl String {
  |      ^^^^^^ the trait `MyTrait` is not implemented for `String`
  |
note: required by a bound in `StringExt`
 --> tests/compile_fail/supertraits_are_actually_included.rs:5:21
  |
5 | #[ext(supertraits = MyTrait)]
  |                     ^^^^^^^ required by this bound in `StringExt`
6 | impl String {
  |      ------ required by a bound in this