error[E0658]: the `#[fundamental]` attribute is an experimental feature --> $DIR/feature-gate-fundamental.rs:1:1 | LL | #[fundamental] | ^^^^^^^^^^^^^^ | = note: see issue #29635 for more information = help: add `#![feature(fundamental)]` to the crate attributes to enable = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0658`.