CORBA23 — Forward declarations and inheritance

Summary: The IDL spec explains forward declarations at the end of section 3.5.2.
However, it does not make the following illegal:

interface base; // Forward declaration

interface derived: base

;

interface base

;

The problem here is that a forward-declared interface is used as a base
interface before the definition for that interface has been seen.
In the absence of further words in the spec, this is legal, but clearly,
it should be illegal (otherwise, I can"t use a single-pass compiler).