#![allow(dead_code, deprecated, unused_variables, unused_mut)]
#![feature(iter_map_windows)]
#[derive(Default)]
struct NonFusedIterator {
    state: i32,
}
impl Iterator for NonFusedIterator {
    type Item = i32;
    fn next(&mut self) -> Option<i32> {
        let val = self.state;
        self.state = self.state + 1;
        if val < 5 || val % 2 == 0 { Some(val) } else { None }
    }
}
fn main() {
    let mut iter = NonFusedIterator::default();
    assert_eq!(iter.next(), Some(0));
    assert_eq!(iter.next(), Some(1));
    assert_eq!(iter.next(), Some(2));
    assert_eq!(iter.next(), Some(3));
    assert_eq!(iter.next(), Some(4));
    assert_eq!(iter.next(), None);
    assert_eq!(iter.next(), Some(6));
    assert_eq!(iter.next(), None);
    assert_eq!(iter.next(), Some(8));
    assert_eq!(iter.next(), None);
    let mut iter = NonFusedIterator::default().map_windows(|arr: &[_; 2]| *arr);
    assert_eq!(iter.next(), Some([0, 1]));
    assert_eq!(iter.next(), Some([1, 2]));
    assert_eq!(iter.next(), Some([2, 3]));
    assert_eq!(iter.next(), Some([3, 4]));
    assert_eq!(iter.next(), None);
    assert_eq!(iter.next(), None);
    assert_eq!(iter.next(), None);
    assert_eq!(iter.next(), None);
}