[PATCH] D136533: [clang] Fix missing diagnostic of declaration use when accessing TypeDecls through typename access

Tue Oct 25 10:30:58 PDT 2022

erichkeane added a comment.

In D136533#3883089 <https://reviews.llvm.org/D136533#3883089>, @mizvekov wrote:

> In D136533#3883048 <https://reviews.llvm.org/D136533#3883048>, @erichkeane wrote:
>
>> One thing you might try is seeing if this is a libcxx-specific thing instead, and try doing a self-build using libcxx.
>
> We tested this on the libc++ CI, as this patch touches a test case in there, and I also tested it on my machine on both windows and linux.
>
> I believe this is a macOS specific issue, and I don't believe the problem is in this patch.
>
> In either case, this seems to be an issue with libc++ that is out there in the wild.
>
> There are likely some cases where folks were using unsupported features for their macOS version, and this bug that we fixed prevented us from correctly diagnosing that.
>
> If I understood everything correctly so far, we can't change shipped libc++.
> So we either:
>
> - Bump the minimum macOS version.
> - Stop using whatever libc++ declared as being unsupported in those old macOS versions.
>
> libc++ gated that feature on a minimum OS version, if you try to use it otherwise, this doesn't compile, as intended.
>
> Would it even be right to add some kind of libc++ specific workaround, if that configuration was declared as unsupported?

I don't believe that the libc++ CI does 'self build with libcxx as the host library', so it would not have caught this.  That said, this could definitely just be an issue in the version that ships with macos, and we cannot really release something that doesn't self-build on one of our supported platforms.

Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D136533/new/

https://reviews.llvm.org/D136533