// [next] compile-flags: -Zlower-impl-trait-in-trait-to-assoc-ty // revisions: current next #![feature(return_position_impl_trait_in_trait)] #![allow(incomplete_features)] trait Foo { fn bar() -> impl std::fmt::Display; } impl Foo for () { fn bar() -> () {} //~^ ERROR `()` doesn't implement `std::fmt::Display` } fn main() {}