aaron.ballman added a comment. In D111400#3088321 <https://reviews.llvm.org/D111400#3088321>, @aaron.ballman wrote:
> In D111400#3088133 <https://reviews.llvm.org/D111400#3088133>, > @hubert.reinterpretcast wrote: > >> In D111400#3087877 <https://reviews.llvm.org/D111400#3087877>, >> @aaron.ballman wrote: >> >>> So your concern is that allowing this patch to be used as an extension in >>> older language modes may change the behavior of existing code? Or is your >>> concern more broad than just this patch? >> >> The behaviour of Clang before this patch in older language modes is >> inconsistent with the specification before P2242R3 (for the template case) >> in such a way that it could appear that P2242R3 is already implemented for >> the template case (but not following the usual convention for extensions >> affecting SFINAE); however, the mechanism by which that occurs might be >> something other than an implementation of P2242R3. >> >> My concern is that the status quo of the Clang implementation with respect >> to this area is broken, which in turn makes it possible for this patch to >> exacerbate the issue by building on top of the brokenness and then making a >> fix more complicated. At the very least, this patch does not demonstrate >> that the "extension" does not affect SFINAE. >> >> In other words, my concern is that this patch is necessarily incomplete >> unless if the situation around the template case is resolved. > > Thank you for the explanation, that's helpful! I'm sympathetic to not wanting > to build on top of an unstable foundation, but I'm also a bit worried that > we're asking a lot of @cor3ntin in terms of this PR because it sounds like > this is a general request to fix template instantiation before doing more > constexpr work (because anything constexpr is generally SFINAE-able). I think > we need to fix the template instantiation issues, but I'm also not certain we > should gate constexpr work on those fixes. > > I'd definitely like to hear thoughts from @rsmith on the right way to proceed. Pinging @rsmith -- I'd like to unblock @cor3ntin. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D111400/new/ https://reviews.llvm.org/D111400 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
