error[E0658]: const generics are unstable
  --> $DIR/feature-gate-const_generics.rs:1:14
   |
LL | fn foo<const X: ()>() {}
   |              ^
   |
   = note: for more information, see https://github.com/rust-lang/rust/issues/44580
   = help: add `#![feature(const_generics)]` to the crate attributes to enable

error[E0658]: const generics are unstable
  --> $DIR/feature-gate-const_generics.rs:3:18
   |
LL | struct Foo<const X: usize>([(); X]);
   |                  ^
   |
   = note: for more information, see https://github.com/rust-lang/rust/issues/44580
   = help: add `#![feature(const_generics)]` to the crate attributes to enable

error: aborting due to 2 previous errors

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