llvm-project

4d323e40 - [libc++] Allow the use of extensions in the implementation (#79532)

[libc++] Allow the use of extensions in the implementation (#79532) We've talked about allowing extensions on [discourse](https://discourse.llvm.org/t/rfc-use-language-extensions-from-future-standards-in-libc/71898/5) and in a libc++ monthly meeting and agreed to test it out in the LLVM 18 release. We've done that with the `tuple` constructor overload set (using conditional `explicit`). Since we haven't heard about any breakages, it seems safe to do. This patch enables the use of extension from later C++ standards inside the versioned `std` namespaces. This should be good enough, since almost all of our code is inside that namespace. This approach also avoids the use of extensions inside the test `std` suite. That part of the code base should stay clean, since it's a test suite that is also used by other vendors to test their implementations.