error[E0741]: `Bar` must implement `ConstParamTy` to be used as the type of a const generic parameter --> $DIR/issue-97278.rs:11:20 | LL | fn test() {} | ^^^ | help: add `#[derive(ConstParamTy)]` to the struct | LL + #[derive(ConstParamTy)] LL | enum Bar { | error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0741`.