| error[E0723]: mutable references in const fn are unstable | |
| --> $DIR/feature-gate-const_mut_refs.rs:5:14 | |
| | | |
| LL | const fn foo(x: &mut i32) -> i32 { | |
| | ^ | |
| | | |
| = note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information | |
| = help: add `#![feature(const_fn)]` to the crate attributes to enable | |
| error: aborting due to previous error | |
| For more information about this error, try `rustc --explain E0723`. |