#![allow(dead_code, deprecated, unused_variables, unused_mut)]
fn main() {
    let iter = (0..10).filter(|x| x % 2 == 0);
    assert_eq!((0, Some(10)), iter.size_hint());
    let iter = (0..10).filter(|x| x % 2 == 0).chain(15..20);
    assert_eq!((5, Some(15)), iter.size_hint());
}