interface Nested {
    str() string
}

struct Leaf {
    name string
}

fn (l Leaf) str() string {
    return l.name
}

fn denest_none() ?Nested {
    return none
}

fn denest_value() ?Nested {
    return Leaf{'leaf'}
}

fn test_dump_string_interpolation_of_option_interface_none() {
    n := denest_none()
    s := dump('${n}')
    assert s == 'Option(none)'
}

fn test_dump_string_interpolation_of_option_interface_value() {
    n := denest_value()
    s := dump('${n}')
    assert s == 'Option(Nested(leaf))'
}