src/test/ui/feature-gates/feature-gate-panic-implementation.stderr

error[E0658]: #[panic_implementation] is an unstable feature (see issue #44489)
  --> $DIR/feature-gate-panic-implementation.rs:18:1
   |
LL | #[panic_implementation] //~ ERROR #[panic_implementation] is an unstable feature (see issue #44489)
   | ^^^^^^^^^^^^^^^^^^^^^^^
   |
   = help: add #![feature(panic_implementation)] to the crate attributes to enable

error: aborting due to previous error

For more information about this error, try `rustc --explain E0658`.