#![allow(dead_code, deprecated, unused_variables, unused_mut)]
fn nobody() -> Option<&'static str> {
    None
}
fn vikings() -> Option<&'static str> {
    Some("vikings")
}
fn main() {
    assert_eq!(Some("barbarians").or_else(vikings), Some("barbarians"));
    assert_eq!(None.or_else(vikings), Some("vikings"));
    assert_eq!(None.or_else(nobody), None);
}