tests/ui/traits/trivial_impl2.rs

//! This test checks that we currently need to implement
//! members, even if their where bounds don't hold for the impl type.

trait Foo<T> {
    fn foo()
    where
        Self: Foo<()>;
}

impl Foo<u32> for () {}
//~^ ERROR: not all trait items implemented, missing: `foo`

fn main() {}