[cfe-dev] Proposal to simplify ObjC Type AST's

[Chris Lattner]

On May 24, 2009, at 1:48 PM, steve naroff wrote:
>>> I think having a common base class (abstract or not) makes either  
>>> of these more appealing than what we have now.
>>
>> This composition enables the "protocol-qualified" concept to be  
>> abstract too.
>>
>
> Hey Chris,
>
> Sounds good to me. I'd simply call it ObjCQualifiedType (or  
> ObjCProtocolQualifiedType).
>
I don't see that this adds any value, what problem does it solve?  Why  
add another set of multiple inheritance?  To me, we should have  
exactly one class for all of this.  The space efficiency issue can be  
easily addressed by tail allocating the array of protocol qualifiers  
(as a second step).

If there is a specific reason that lots of clients want to use  
dyn_cast to determine if an interface pointer has protocol qualifiers  
(instead of using ->getNumQualifiers() != 0), we can definitely add  
helper classes for that.  I just don't think we should make a big  
class hierarchy for no reason.

-Chris