[clang] [clang] Fix implicit integer conversion for opaque enums declared in class templates (PR #121039)

[Erich Keane via cfe-commits]

=?utf-8?q?André?= Brand <andre.brand at mailbox.org>
Message-ID:
In-Reply-To: <llvm.org/llvm/llvm-project/pull/121039 at github.com>


erichkeane wrote:

> @erichkeane I am not sure what you mean. As I pointed out earlier, the examples @cor3ntin brought up actually conform to the standard as in [[temp.spec.general]](https://wg21.link/temp.spec#temp.inst-3):
> 
> > The implicit instantiation of a class template specialization causes the implicit instantiation of the declarations, but not of the definitions of [...] scoped member enumerations, [...]
> 
> The issues are correctly diagnosed by clang if the struct is _explicitly instantiated_ as demonstrated here in Compiler Explorer: https://godbolt.org/z/GzYq9jzjo.

My quick look through the ActOnEnum and this function looked like it showed some misses.  If Corentin is comfortable with our checking here, then I'm happy too.

> 
> Nevertheless, I investigated further and managed to discover some real bugs with diagnostics on template instantiation. These affect not only enums but also nested classes. If you are interested, you can have a look: https://godbolt.org/z/vKG6vqWhs. I have already started working on these issues but so far they seem unrelated.

Thats great, thanks for finding that and working on it!  Those look like some pretty unfortunate misses.
> 
> I plan to keep working on it but I can't promise much given the facts that I only have the weekends to spend time on it and my limited familiarity with the codebase (this would be my very first commit to LLVM). But, of course, I promise to try my best! 🙂

Definitely appreciate it!

I'm happy when Corentin is here, I have no concerns.



https://github.com/llvm/llvm-project/pull/121039