[cfe-dev] Problems with injected-class-name in decl list for class template specializations

[Richard Smith via cfe-dev]

On 12 May 2018 at 04:03, Andrew Rogers <Andrew.Rogers at wdc.com> wrote:

> Hi Argyrios, Richard,
>
>
>
> I raised PR37399 <https://llvm.org/PR37399> and have been discussing how
> to fix it with Reid.
>
>
>
> The root of the problem is an interaction between the MSCXXABI code and
> the fact that an injected-class-name is inserted into the decl list for
> class template specializations after the MSCXXABI code has added an
> attribute to the decl for the class template specialization (in a case
> involving a dependent base of the class template where the MSCXXABI code is
> invoked before the injected-class-name is instantiated).
>
>
>
> The two options for fixing this problem either involve working around the
> fact that the injected-class-name is inserted into the decl list for the
> class template specialization by copying the MSCXXABI attribute to the
> injected-class-name decl when it’s added to the list (this works but feels
> ugly), or not inserting the injected-class-name into the decl list for the
> class template specialization (this causes a number of other tests to fail,
> possibly because ClassTemplateSpecializationDecl::getMostRecentDecl()
> explicitly works around the fact that there will be injected-class-names in
> the decl list for class template specializations, though as yet
> unconfirmed).
>
>
>
> I have noticed that you have both put comments on
> ClassTemplateSpecializationDecl::getMostRecentDecl() which seem to
> suggest the fact that the injected-class-name is inserted into the decl
> list for the class template specialization seems to be an error in and of
> itself. Does it make more sense to try and clean up the fact that
> injected-class-names are inserted into the decl list, resulting in a
> broader change, or just try and point-fix the MSCXXABI issue?
>

I think it makes sense to try to clean this up more generally, if you're
interested in giving that a go. Here's the design that I would try: add a
new TypeDecl subclass for the injected-class-name (maybe
InjectedClassNameDecl), and represent the injected-class-name of all
classes as an InjectedClassNameDecl rather than a CXXRecordDecl.

I’m a clang newbie, so would appreciate any feedback you could give – TIA!
> Further details are in PR37399 <https://llvm.org/PR37399>.
>
>
>
> Yours, Andrew R
>
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