impl trait vec !

main.rs

trait MakesNoise {
    fn make_noise(self) -> ();
}

struct Dog;
struct Cat;

impl MakesNoise for Dog {
    fn make_noise(self) -> () {
        println!("WOOF WOOF");
        // Who let the dogs out ?
    }
}

impl MakesNoise for Cat {
    fn make_noise(self) -> () {
        println!("Everybody wants to be a cat !");
        // Because the cat's the only cat, who knows where it's at
    }
}

fn make_some_noise(animals: Vec<impl MakesNoise>) -> () {
    for thing in animals {
        thing.make_noise();
    }
}

fn main() -> () {
    let a = Dog {};
    let b = Cat {};
    let animals: Vec<impl MakesNoise> = vec![a, b]; // `impl Trait` not allowed outside of function and inherent method return types
    make_some_noise(animals);

    a.make_noise();
    b.make_noise();
}