Speculatively implement LWG-4139 [time.zone.leap] recursive constraint in <=>#4902
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StephanTLavavej merged 3 commits intomicrosoft:mainfrom Aug 25, 2024
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CaseyCarter
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Aug 21, 2024
| bool _Is_positive; | ||
| seconds _Elapsed_offset; | ||
| }; | ||
| _NODISCARD friend constexpr bool operator==(const leap_second& _Left, const leap_second& _Right) noexcept { |
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No change requested: I don't think we need a comment here to indicated speculative implementation of LWG-4139, despite that this is a fairly big change and that LWG hasn't yet signed off on a proposed resolution. LWG has demonstrated approval of the "make leap_second's operators hidden friends" approach, and both libc++ and libstdc++implement it, so I have no doubt this will be the eventual resolution of the issue.
StephanTLavavej
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Aug 21, 2024
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I'm mirroring this to the MSVC-internal repo - please notify me if any further changes are pushed. |
<=><=>
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Thanks for the preventative spaceship maintenance! 🔧 🛸 🪄 |
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LWG-4139 indicated constraint recursion in the current specification of the
operator<=>forleap_secondandsys_time, which is not yet revealed due to the bugs in MSVC and (old versions of) Clang.Although the proposed resolution is not shown in the LWG issue, I think the necessary changes are clear enough - just moving the operator functions from the synopsis of
<chrono>to that ofstd::chrono::leap_secondand addingfriend.This has been done in libstdc++ years ago (gcc-mirror/gcc@1736bf5), and recently in libc++ via LLVM-104713.