type_from_specialization.rs

#![feature(specialization)]

struct Foo;
struct No;
struct Yes;

trait Bar {
    type Result;
}

impl<T> Bar for T {
    default type Result = No;
}

impl Bar for Foo {
    type Result = Yes;
}

trait Baz {
    fn foo(&self) {
        println!("Hi");
    }
}

impl<T: Bar<Result=Yes>> Baz for T {}

fn main() {
    Foo.foo();
}