1 error[E0658]: the `#[rustc_variance]` attribute is just used for rustc unit tests and will never be stable
2 --> $DIR/feature-gate-rustc-attrs-1.rs:5:1
7 = help: add `#![feature(rustc_attrs)]` to the crate attributes to enable
9 error[E0658]: the `#[rustc_error]` attribute is just used for rustc unit tests and will never be stable
10 --> $DIR/feature-gate-rustc-attrs-1.rs:6:1
15 = help: add `#![feature(rustc_attrs)]` to the crate attributes to enable
17 error[E0658]: the `#[rustc_nonnull_optimization_guaranteed]` attribute is just used to enable niche optimizations in libcore and will never be stable
18 --> $DIR/feature-gate-rustc-attrs-1.rs:7:1
20 LL | #[rustc_nonnull_optimization_guaranteed]
21 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
23 = help: add `#![feature(rustc_attrs)]` to the crate attributes to enable
25 error: aborting due to 3 previous errors
27 For more information about this error, try `rustc --explain E0658`.