1 error[E0658]: the `#[rustc_on_unimplemented]` attribute is an experimental feature (see issue #29628)
2 --> $DIR/feature-gate-on-unimplemented.rs:14:1
4 LL | #[rustc_on_unimplemented = "test error `{Self}` with `{Bar}`"]
5 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
7 = help: add #![feature(on_unimplemented)] to the crate attributes to enable
9 error: aborting due to previous error
11 For more information about this error, try `rustc --explain E0658`.