import time

interface InterfaceObject {
mut:
    duration ?time.Duration
    update()
}

struct Object {
mut:
    duration ?time.Duration
}

fn (mut obj Object) update() {
    duration := obj.duration or { time.second }
    println(duration)
}

struct FooObject {
    Object
}

fn (mut obj FooObject) update() {
    duration := obj.duration or { time.millisecond * 500 }
    println(duration)
}

fn test_interface_with_option_field() {
    mut object := InterfaceObject(FooObject{})
    println(object)
    assert '${object.duration}' == 'Option(none)'
}