// run-pass fn select<'r>(x: &'r Option, y: &'r Option) -> &'r Option { match (x, y) { (&None, &None) => x, (&Some(_), _) => x, (&None, &Some(_)) => y } } pub fn main() { let x = None; let y = Some(3); assert_eq!(select(&x, &y).unwrap(), 3); }