struct A {

}

impl C for A {
    fn test1(&self) -> String {
        return String::from("test #1");
    }
}

struct B {

}

impl C for B {
    fn test1(&self) -> String {
        return String::from("test #1");
    }
}

impl D for B {
    fn test2(&self) -> String {
        return String::from("test #2");
    }
}

trait C {
    fn test1(&self) -> String;
}

trait D : C {
    fn test2(&self) -> String;
}

fn main() {
    let a = A{};
    let b = B{};
    println!("{}", a.test1());
    println!("{}", b.test2());
}