#![feature(adt_const_params)] //~^ WARN the feature `adt_const_params` is incomplete and may not be safe to use and/or cause compiler crashes [incomplete_features] #[derive(PartialEq, Eq)] enum Nat { Z, S(Box<Nat>), } fn foo<const N: Nat>() {} //~^ ERROR `Nat` must implement `ConstParamTy` to be used as the type of a const generic parameter fn main() {}