[libcxx-commits] [libcxx] Adds back special-case for booleans in std::variant gated by _LIBCPP_ENABLE_NARROWING_CONVERSIONS_IN_VARIANT. (PR #73121)

[Louis Dionne via libcxx-commits]

ldionne wrote:

I see, thanks for the context. In the future, I suggest including that information in the original PR message since you should expect us to ask this very question.

In order to determine what we want to do with this, I'd like to have a bit more information:
1. Can you share some examples of compilation errors you're seeing after this change? Are they vexing or are they stuff where the code was clearly wrong in the first place?
2. Same for runtime errors -- this is actually way more worrisome.
3. http://wg21.link/p1957 actually explores the impact on some large code bases like Google's code base. It says it found 2 issues, which seems to be incorrect. @zhihaoy can you provide more context since you authored the paper?

At the moment, I'm trying to figure out whether this is serious enough that we need to offer a transition path for everyone for one release, or whether this is even more serious and we need to bring this up in WG21. Or whether this is actually OK, none of the issues are vexing and basically this isn't something we'd want to work around upstream. Everything's on the table, but I'd like more information to help inform that decision.

https://github.com/llvm/llvm-project/pull/73121