trait Trait {
    fn f(&self);
}

impl Trait for u32 {
    fn f(&self) {
        print!("1");
    }
}

impl<'a> Trait for &'a i32 {
    fn f(&self) {
        print!("2");
    }
}

fn main() {
    let x = &0;
    x.f();
}