fn main() {
    trait Label { fn label(&self) -> &str; }
    struct Tray;
    struct Basket;
    impl Label for Tray { fn label(&self) -> &str { "tray" } }
    impl Label for Basket { fn label(&self) -> &str { "basket" } }
    let items: Vec<Box<dyn Label>> = vec![Box::new(Tray), Box::new(Basket)];
    assert_eq!(items.iter().map(|x| x.label()).collect::<Vec<_>>(), vec!["tray","basket"]);
    println!("Dynamic labels: tray, basket");
}