#![allow(dead_code, deprecated, unused_variables, unused_mut)]
fn main() {
    let yep = Some(42);
    let nope = None;
    let nums: Vec<i32> = (0..4).chain(yep).chain(4..8).collect();
    assert_eq!(nums, [0, 1, 2, 3, 42, 4, 5, 6, 7]);
    let nums: Vec<i32> = (0..4).chain(nope).chain(4..8).collect();
    assert_eq!(nums, [0, 1, 2, 3, 4, 5, 6, 7]);
}