i = !0

@Inheritable
C = Class()
C::[<: Self]
    __init__! self =
        print! "initialize C:", self
        i.inc!()
    __del__! self =
        print! "delete C:", self
        i.dec!()

p!() =
    c = C.new()
    assert i == 1
    print! c

p!()
assert i == 0

D = Inherit C, Additional := { x = Int }
D::[<: Self]
    @Override
    __init__! self =
        C::__init__! self
        print! "initialize D:", self, self::x

_ = D.new { x = 1 }