1 error[E0658]: unions in const fn are unstable
2 --> $DIR/feature-gate-const_fn_union.rs:12:5
7 = note: see issue #51909 <https://github.com/rust-lang/rust/issues/51909> for more information
8 = help: add `#![feature(const_fn_union)]` to the crate attributes to enable
10 error: aborting due to previous error
12 For more information about this error, try `rustc --explain E0658`.