1 error[E0658]: unions in const fn are unstable (see issue #51909)
2 --> $DIR/feature-gate-const_fn_union.rs:21:5
4 LL | Foo { u }.i //~ ERROR unions in const fn are unstable
7 = help: add #![feature(const_fn_union)] to the crate attributes to enable
9 error: aborting due to previous error
11 For more information about this error, try `rustc --explain E0658`.