#![allow(dead_code, deprecated, unused_variables, unused_mut)]
use std::iter;
#[derive(PartialEq, Debug)]
struct Expensive;
fn main() {
    let mut things = iter::repeat_with(|| Expensive);
    assert_eq!(Some(Expensive), things.next());
    assert_eq!(Some(Expensive), things.next());
    assert_eq!(Some(Expensive), things.next());
    assert_eq!(Some(Expensive), things.next());
    assert_eq!(Some(Expensive), things.next());
}