#![allow(dead_code, deprecated, unused_variables, unused_mut)]
fn main() {
    let xs = [1, 2, 3];
    let mut iter = xs.into_iter().peekable();
    assert_eq!(iter.peek_mut(), Some(& mut 1));
    assert_eq!(iter.peek_mut(), Some(& mut 1));
    assert_eq!(iter.next(), Some(1));
    if let Some(p) = iter.peek_mut() {
        assert_eq!(* p, 2);
        *p = 1000;
    }
    assert_eq!(iter.collect::< Vec < _ >> (), vec![1000, 3]);
}