error[E0658]: the `#[rustc_on_unimplemented]` attribute is an experimental feature (see issue #29628)
- --> $DIR/feature-gate-on-unimplemented.rs:14:1
+ --> $DIR/feature-gate-on-unimplemented.rs:4:1
|
LL | #[rustc_on_unimplemented = "test error `{Self}` with `{Bar}`"]
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^