mizvekov added a comment. In D99005#2860598 <https://reviews.llvm.org/D99005#2860598>, @Quuxplusone wrote:
> I have no strong/well-informed opinions here. I have an idea to offer, //if// > there is precedent for it. My idea is, keep it as an error if the rvalue > resolution finds nothing, but (1) fall back to an lvalue resolution //for > error-recovery purposes//, and (2) suppress the error in system headers. > Then, the usage in MSVC STL will keep working but only because it's in a > system header. I seem to recall that there is precedent for diagnostics that > are "non-downgradable error in user code, yet still suppressed in system > headers." If I'm imagining things, then please do not invent such a facility > purely for this feature. That would still leave the effect of changing the deduced type of a `decltype(auto)` returning function. But I am on the same boat here in that I am not sure if you are imagining things as well :) > My second choice is to do whatever minimalistic hack suffices to satisfy the > customer (Aaron etc. in this case), but only with the understanding that we > plan to eliminate that hack as soon as MSVC STL gets updated. My third choice > is to revert the whole thing and then land a new version of it that always > falls back to lvalue resolution, but with an on-by-default //warning// (not > error) (so this would probably affect a ton of your test cases); then the > user can downgrade that warning as a workaround. Again, the change in flow where we make the expression an xvalue early and definitively before return type deduction occurs makes things more complicated. My vote is the second choice, as I think making a workaround where we temporarily do the C++20 thing only in some contexts is far simpler, specially if we don't have to update a ton of test cases to cover it :) Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D99005/new/ https://reviews.llvm.org/D99005 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
