#![allow(unused_variables)]
fn main() {
    let mut string = String::from("abcde");
    string.extend_from_within(2..);
    assert_eq!(string, "abcdecde");
    string.extend_from_within(..2);
    assert_eq!(string, "abcdecdeab");
    string.extend_from_within(4..8);
    assert_eq!(string, "abcdecdeabecde");
}