struct A {
    x: [u32; 3],
}

impl A {
    fn iter<'a>(&'a self) -> impl Iterator<Item=u32> + 'a {
        (0..3).filter(move |&i| self.x[i] != 0).map(move |i| self.x[i])
    }
}

fn main() {
    let a = A { x : [0, 1, 2]};
    for el in a.iter() {
        println!("{}", el);
    }
}