mizvekov wrote:
> The comments in this area are confusing me, FWIW:
>
> ```
> /// Stores the TagDecl associated with this type. The decl may point to any
> /// TagDecl that declares the entity.
> TagDecl *decl;
>
> ...
>
> TagDecl *getOriginalDecl() const { return decl; }
> ```
>
> The function is called "get original decl" which implies you get the first
> declaration seen in the TU, but the data member it returns has a comment
> saying it may point to any declaration in the redeclaration chain. One of
> these is wrong, correct?
Yeah, that is describing what is valid from the point of view of the AST Node.
As a user of TagType, you can certainly create one which points to any
declaration of an entity, and all of these nodes which point to a declaration
of the same entity are the same type.
>From the point of view of Sema, there are further rules on how these types are
>created, in normal day-to-day source code parsing, the declaration pointed to
>by a non-canonical TagType will be the one found by lookup at that point in
>the program.
FWIW the name `getOriginalDecl` was picked to temporarily disambiguate from the
behavior of the original `getDecl` that existed before the patch.
The difference in behavior is such that `getDecl` would always return the
definition if that existed, otherwise it would return the very first
declaration ever found by typename lookup when parsing a program, as there only
existed one TagType per entity.
The problem with keeping the name is that the behavior change meant that
whenever I would rebase the patch, new users of getDecl would have popped up
and it would be hard to make sure all uses of it were correct. By changing the
name, I get a compilation error which would allow me to inspect and make the
necessary changes.
As I stated before, once this patch is settled and everyone has had a nice
window to rebase their upstream, my plan is to submit another patch renaming
getOriginalDecl back to getDecl.
https://github.com/llvm/llvm-project/pull/147835
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