#![allow(dead_code, deprecated, unused_variables, unused_mut)]
use std::time::Duration;
fn main() {
    assert_eq!(
        Duration::new(0, 1).checked_sub(Duration::new(0, 0)), Some(Duration::new(0, 1))
    );
    assert_eq!(Duration::new(0, 0).checked_sub(Duration::new(0, 1)), None);
}