tu.rs

trait Foo {
    fn new() -> Self;
}

struct Bar(int, int);

impl Foo for Bar {
    fn new() -> Bar {
        Bar(1, 2)
    }
}

impl Foo for (int, int) {
    fn new() -> (int, int) {
        (3, 4)
    }
}

fn main() {
    let ts = Foo::new::<Bar>();
}