error[E0658]: repr with 128-bit type is unstable --> $DIR/E0658.rs:2:1 | LL | enum Foo { | ^^^^^^^^ | = note: see issue #56071 for more information = help: add `#![feature(repr128)]` to the crate attributes to enable = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0658`.