error[E0658]: diagnostic items compiler internal support for linting --> $DIR/diagnostic_item.rs:1:1 | LL | #[rustc_diagnostic_item = "foomp"] | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | = help: add `#![feature(rustc_attrs)]` to the crate attributes to enable error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0658`.