Identity of interfaces (or not)

[BCS]

Reply to Tomas,

> The problem is that B has two vtables that implement the interface I.
> However, in A.addChild, i.parent get's the first one (introduced by
> A), and in main, it gets the second one (J , which derived from I).
> The identity check then fails because the pointers aren't the same,
> even though it's the same object in question.

why not make
  Ia == Ib
into
  cast(Object)Ia == cast(Object)Ib
?
 
> So is it a bug? Or is identity for interfaces simply not guaranteed to
> pass, even when it's the same Object in question?
> 
> Thanx
> - Tomas