[libcxx-commits] [clang] [libcxx] Reapply "[Clang] Implement resolution for CWG1835 (#92957, #98547)" (PR #100425)

[Krystian Stasiowski via libcxx-commits]

sdkrystian wrote:

CWG reviewed [CWG2920](https://cplusplus.github.io/CWG/issues/2920.html) during the 08-16 teleconference:
> The resolution for [issue 1835](https://cplusplus.github.io/CWG/issues/1835.html) in P1787 has addressed real concerns. CWG recognizes that real-world code now no longer compiles, although the fix for the affected source code is trivial. A limited exception to support some of the existing code might be feasible. CWG solicits a paper with specification and analysis.

[The meeting minutes](https://wiki.edg.com/bin/view/Wg21telecons2024/Teleconference2024-08-16#CWG2920) portray a general feeling of apathy from CWG for code broken by the resolution. With the enhanced detection and recovery from missing `template` keywords implemented in this PR (see [my comment](https://github.com/llvm/llvm-project/pull/100425#issuecomment-2258973782) for examples; all cases reported by users are addressed), I feel that we can go ahead with relanding this patch. WDYT @AaronBallman, @cor3ntin, and @mizvekov?

https://github.com/llvm/llvm-project/pull/100425