#![allow(dead_code, deprecated, unused_variables, unused_mut)]
fn make_iter(do_insert: bool) -> impl Iterator<Item = i32> {
    match do_insert {
        true => return (0..4).chain(Some(42)).chain(4..8),
        false => return (0..4).chain(None).chain(4..8),
    }
}
fn main() {
    println!("{:?}", make_iter(true).collect::< Vec < _ >> ());
    println!("{:?}", make_iter(false).collect::< Vec < _ >> ());
}