struct Dog {
    breed string
}

struct Cat {
    breed string
}

fn (d Dog) speak() string {
    return 'woof'
}

fn (c Cat) speak() string {
    return 'meow'
}

interface Speaker {
    breed string
    speak() string
}

fn test_array_of_interface_init() {
    dog := Dog{'Leonberger'}
    cat := Cat{'Siamese'}

    mut rets := []string{}

    for item in [Speaker(dog), cat] {
        println(item.speak())
        rets << item.speak()
    }

    assert rets.len == 2
    assert rets[0] == 'woof'
    assert rets[1] == 'meow'
}