#![allow(dead_code, deprecated, unused_variables, unused_mut)]
fn main() {
    let mut iter = [1, 2, 3].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 = &5;
    }
    assert_eq!(iter.collect::< Vec < _ >> (), vec![& 5, & 3]);
}