[dllthomas]

This would seem to be "just" a matter of correctly handling polymorphism along yet another axis.

Let's say we had the following C++ code:

    int foo(int (*bar)(char), int (*baz)(), char c) {
        try {
            return bar(c)
        } catch(SomeException &e) {
            raise otherexception;
        }
    }

What exceptions can be raised by foo?

The answer is simply computed - "anything raised by its first argument except SomeException, plus the type of otherexception".

Such a system would be tremendously more flexible than Java's checked exceptions, while still allowing you to confidently restrict what might be thrown in a section of code.