[cfe-dev] ParseTag only called from ParseEnumSpecifier

[Ted Kremenek]

I noticed today that ParseTag is only called by ParseEnumSpecifier.   
In the past ParseTag was used do much of the heavy lifting of parsing  
structs, unions, and enums, and the comments on the source still say  
this.  Now it looks like ParseTag is only called by  
ParseEnumSpecifier, which means most of the comments are not true and  
that the logic could probably just be rolled into ParseEnumSpecifier  
directly.

 From my understanding of the code, it appears that  
ParseClassSpecifier (in ParseDeclCXX.cpp) now does all the parsing for  
structs, unions, and C++ classes.  This seems a little weird to me,  
and it isn't clear from the comments in the Parse library that this is  
the case.  Specifically, I have two concerns:

(1) ParseTag now appears to be somewhat redundant and unnecessary, and  
in some ways ill-named.  It doesn't appear to serve its original  
purpose anymore, and thus it's logic should probably just be folded  
into ParseEnumSpecifier.

(2) It seems strange to me that parsing structs and unions, core  
pieces of the C language, is done in ParseClassSpecifier  
(ParseDeclCXX.cpp).  There seems to be a lot of commonality here that   
could possibly be refactored and moved back into ParseDecl.cpp.  This  
is my first look at this code in a while, so I'm don't claim to  
understand all of the design decisions here, but conceptually it just  
seems a little confusing.

As a side note, my original interest in this code was to allow the  
parser+actions to be able to distinguish up front between enum/struct/ 
union/class forward declarations and definitions.  This would allow us  
to hopefully clean up some elements of the ASTs with regards to  
forward declarations of tag types, and it seems it would also relay  
more information to the parser Actions.