src/test/ui/associated-types/associated-types-overridden-binding.rs

#![feature(trait_alias)]

trait Foo: Iterator<Item = i32> {}
trait Bar: Foo<Item = u32> {} //~ ERROR type annotations required

trait I32Iterator = Iterator<Item = i32>;
trait U32Iterator = I32Iterator<Item = u32>;

fn main() {
    let _: &dyn I32Iterator<Item = u32>;
}