[libcxx-commits] [libcxx] [libc++] LWG4497: `std::nullopt_t` should be comparable (PR #195549)

[Hristo Hristov via libcxx-commits]

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@@ -362,6 +362,16 @@ struct nullopt_t {
     explicit __secret_tag() = default;
   };
   _LIBCPP_HIDE_FROM_ABI constexpr explicit nullopt_t(__secret_tag, __secret_tag) noexcept {}
+#    if _LIBCPP_STD_VER <= 17
+  _LIBCPP_HIDE_FROM_ABI constexpr friend bool operator==(nullopt_t, nullopt_t) { return true; }
+  _LIBCPP_HIDE_FROM_ABI constexpr friend bool operator!=(nullopt_t, nullopt_t) { return false; }
+  _LIBCPP_HIDE_FROM_ABI constexpr friend bool operator>(nullopt_t, nullopt_t) { return false; }
+  _LIBCPP_HIDE_FROM_ABI constexpr friend bool operator<(nullopt_t, nullopt_t) { return false; }
+  _LIBCPP_HIDE_FROM_ABI constexpr friend bool operator>=(nullopt_t, nullopt_t) { return true; }
+  _LIBCPP_HIDE_FROM_ABI constexpr friend bool operator<=(nullopt_t, nullopt_t) { return true; }
+#    else
+  _LIBCPP_HIDE_FROM_ABI constexpr friend strong_ordering operator<=>(nullopt_t, nullopt_t) = default;
+#    endif
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Zingam wrote:

This make sense. Still, wouldn't it be more user-friendly to be explicit or will it be a bad practice?


https://github.com/llvm/llvm-project/pull/195549