error[E0658]: allow_internal_unsafe side-steps the unsafe_code lint
  --> $DIR/feature-gate-allow-internal-unsafe-nested-macro.rs:18:9
   |
LL |         #[allow_internal_unsafe] //~ ERROR allow_internal_unsafe side-steps
   |         ^^^^^^^^^^^^^^^^^^^^^^^^
...
LL | bar!();
   | ------- in this macro invocation
   |
   = help: add #![feature(allow_internal_unsafe)] to the crate attributes to enable

error: aborting due to previous error

If you want more information on this error, try using "rustc --explain E0658"