src/test/ui/traits/trait-alias/trait-alias-object-fail.rs

#![feature(trait_alias)]

trait EqAlias = Eq;
trait IteratorAlias = Iterator;

fn main() {
    let _: &dyn EqAlias = &123;
    //~^ ERROR the trait `std::cmp::Eq` cannot be made into an object [E0038]
    let _: &dyn IteratorAlias = &vec![123].into_iter();
    //~^ ERROR must be specified
}