fn test_interface_embedding_method_call() {
    mut window := &Window{}
    btn := &Button{}
    window.initables << btn
    window.run()
}

@[heap]
pub struct Window {
mut:
    initables []Initable
    popview   PopView = DummyPopup{}
}

interface Initable {
mut:
    init(&Window)
}

interface Drawable {
    draw()
}

pub fn (mut window Window) run() {
    for mut i in window.initables {
        i.init(window)
    }
    for wd in window.initables {
        if wd is Drawable {
            d := wd as Drawable
            d.draw()
        }
    }
    window.popview.draw()
}

struct DummyPopup {}

fn (d DummyPopup) draw() {}

interface PopView {
    Drawable
}

@[heap]
pub struct Button {
mut:
    window &Window = unsafe { nil }
}

pub fn (mut b Button) init(window &Window) {
    b.window = window
}

pub fn (b Button) draw() {
    g := b.window.initables
    println(g.len)
    assert g.len == 1
}