error[E0658]: the `#[fundamental]` attribute is an experimental feature
  --> $DIR/feature-gate-fundamental.rs:1:1
   |
LL | #[fundamental]
   | ^^^^^^^^^^^^^^
   |
   = note: for more information, see https://github.com/rust-lang/rust/issues/29635
   = help: add `#![feature(fundamental)]` to the crate attributes to enable

error: aborting due to previous error

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