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 = note: see issue #29642 <https://github.com/rust-lang/rust/issues/29642> for more information
8 = help: add `#![feature(rustc_attrs)]` to the crate attributes to enable
10 error[E0658]: the `#[rustc_error]` attribute is just used for rustc unit tests and will never be stable
11 --> $DIR/feature-gate-rustc-attrs-1.rs:6:1
16 = note: see issue #29642 <https://github.com/rust-lang/rust/issues/29642> for more information
17 = help: add `#![feature(rustc_attrs)]` to the crate attributes to enable
19 error[E0658]: the `#[rustc_nonnull_optimization_guaranteed]` attribute is just used to enable niche optimizations in libcore and will never be stable
20 --> $DIR/feature-gate-rustc-attrs-1.rs:7:1
22 LL | #[rustc_nonnull_optimization_guaranteed]
23 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
25 = note: see issue #29642 <https://github.com/rust-lang/rust/issues/29642> for more information
26 = help: add `#![feature(rustc_attrs)]` to the crate attributes to enable
28 error: aborting due to 3 previous errors
30 For more information about this error, try `rustc --explain E0658`.