error[E0658]: this is an internal attribute that will never be stable
  --> $DIR/gate-do-not-const-check.rs:1:1
   |
LL | #[rustc_do_not_const_check]
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = help: add `#![feature(rustc_attrs)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

error: aborting due to 1 previous error

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