trait Moo {
    fn moo(&self) -> String;
}

trait SuperMoo: Moo {
    fn supermoo(&self) {
        println!("Super! {}", self.moo());
    }

    fn supercow() {
        println!("SuperCow!");
    }
}

struct Cow {

}

impl Moo for Cow {
    fn moo(&self) -> String {
        "MOOOOO".to_string()
    }
}

fn main() {
    let c = Cow{};
    let m = Box::new(c) as Box<Moo>;
    <c as SuperMoo>::supercow();
}