type Baz = Foo

@[heap]
struct Foo {
    a  int    = 123
    b  string = 'b'
    cb ?fn (&Foo)
}

@[heap]
struct Bar {
    a  int    = 321
    b  string = 'a'
    cb ?fn (&Baz)
}

fn g(a Foo) Foo {
    return a
}

fn t(a Bar) Foo {
    return g(a: 123, b: 'foo', cb: a.cb)
}

fn test_main() {
    a := Foo{
        cb: none
    }

    b := Foo{
        cb: fn (a &Foo) {
        }
    }

    w := Bar{
        cb: b.cb
    }

    z := Bar{
        cb: a.cb
    }

    t(a: 1, cb: a.cb)
    t(a: 2, cb: b.cb)
    t(a: 3, cb: w.cb)
    t(a: 4, cb: z.cb)
}