#![allow(dead_code, deprecated, unused_variables, unused_mut)]
#[derive(Debug)]
struct MyCollection(Vec<i32>);
impl MyCollection {
    fn new() -> MyCollection {
        MyCollection(Vec::new())
    }
    fn add(&mut self, elem: i32) {
        self.0.push(elem);
    }
}
impl Extend<i32> for MyCollection {
    fn extend<T: IntoIterator<Item = i32>>(&mut self, iter: T) {
        for elem in iter {
            self.add(elem);
        }
    }
}
fn main() {
    let mut c = MyCollection::new();
    c.add(5);
    c.add(6);
    c.add(7);
    c.extend(vec![1, 2, 3]);
    assert_eq!("MyCollection([5, 6, 7, 1, 2, 3])", format!("{c:?}"));
}