tests/ui/type-alias-impl-trait/type-alias-impl-trait-fn-type.rs

#![feature(type_alias_impl_trait)]
#![allow(dead_code)]

// FIXME: this is ruled out for now but should work

type Foo = fn() -> impl Send;
//~^ ERROR: `impl Trait` only allowed in function and inherent method argument and return types

fn make_foo() -> Foo {
    || 15
}

fn main() {}