error[E0658]: use of an internal attribute
  --> $DIR/diagnostic_item.rs:1:1
   |
LL | #[rustc_diagnostic_item = "foomp"]
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = help: add `#![feature(rustc_attrs)]` to the crate attributes to enable
   = note: the `#[rustc_diagnostic_item]` attribute allows the compiler to reference types from the standard library for diagnostic purposes

error: aborting due to 1 previous error

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