[llvm-branch-commits] [libcxx] [libc++] Remove the need for _LIBCPP_TEMPLATE_VIS (PR #133010)

[Louis Dionne via llvm-branch-commits]

https://github.com/ldionne requested changes to this pull request.

I am fine with the spirit of this patch. I think it needs a release note though since we're making library-wide changes. We don't think those changes are going to affect anyone, but I think it's a nice courtesy to give our users and it doesn't cost us anything to call it out.

Also, I'd like this patch to be split into two. First, the changes that introduce `NAMESPACE_VIS` and that make `TEMPLATE_VIS` a no-op. Then, one or two weeks after landing the first patch, we can have a second patch that removes `_LIBCPP_TEMPLATE_VIS`, which is now a no-op. I think this will simplify things in case we need to revert the patch for an unforeseen reason, and it'll allow people who do wonky stuff (e.g. override `_LIBCPP_TEMPLATE_VIS` for their own purposes) to apply a temporary workaround while they figure out how not to do something unsupported. Again, that's low cost to us and it'll make things much easier for everyone in case things happen to go wrong, unexpectedly.

https://github.com/llvm/llvm-project/pull/133010