[cfe-dev] A small proposal about TagType's and source ranges

[John McCall]

On Mar 13, 2011, at 12:38 AM, Abramo Bagnara wrote:

> Il 13/03/2011 05:34, John McCall ha scritto:
>> 
>> On Mar 12, 2011, at 11:28 AM, Abramo Bagnara wrote:
>> 
>>> Il 12/03/2011 20:10, John McCall ha scritto:
>>>> 
>>>> On Mar 12, 2011, at 8:54 AM, Abramo Bagnara wrote:
>>>> 
>>>>> 
>>>>> We are struggling to fix lack of proper source location range for
>>>>> TagType's due to missing setting of both source location for tag keyword
>>>>> and name.
>>>>> 
>>>>> We'd like to propose the following simplification of current approach to
>>>>> tag types and elaborated types storing:
>>>>> 
>>>>> Currently clang uses (only in C++) an ElaboratedType whenever the type
>>>>> has an explicit class/struct/union/enum keyword *or* a name qualifier.
>>>>> 
>>>>> We propose to use an ElaboratedType *only* whenever there is a name
>>>>> qualifier and to add to TagTypeLoc a (possibly invalid) tag keyword
>>>>> location (removing the one now available in ElaboratedTypeLoc).
>>>> 
>>>> How would we represent "struct A::B" in C++?
>>>> 
>>>> It's also important to distinguish between A and struct A in C++.  If we don't have an elaborated type node, what remembers this distinction?
>>> 
>>> On the syntactic side they can be distinguished in the TagTypeLoc using
>>> the validity of tag keyword location. On the semantic side they can be
>>> distinguished inheriting TagType from TypeWithKeyword.
>> 
>> 
>> Adding non-canonical state to TagType is not really acceptable;  it's really,
>> really nice right now that TagTypes are always canonical.
> 
> If you prefer in this way the inheritance from TypeWithKeyword can be
> avoided. Do we need to distinguish between "S" and "struct S" in places
> where TypeLoc is not available?

Generally not, but I'd rather not rely on it.  Wouldn't the better solution
to have some mode which enables ElaboratedTypes even in C?

John.