[libcxx-commits] [libcxx] [libc++] Make std::pair trivially copyable if its members are (PR #89652)

[Louis Dionne via libcxx-commits]

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@@ -74,6 +75,31 @@ struct _LIBCPP_TEMPLATE_VIS pair
   _LIBCPP_HIDE_FROM_ABI pair(pair const&) = default;
   _LIBCPP_HIDE_FROM_ABI pair(pair&&)      = default;
 
+  // Make pair trivially copyable if we have a way to do it
+  static const bool __enable_defaulted_assignment_operators =
+      !is_reference<first_type>::value && !is_reference<second_type>::value;
+#if _LIBCPP_STD_VER >= 20 && defined(_LIBCPP_ABI_TRIVIALLY_COPYABLE_PAIR)
+  static const bool __has_defaulted_members = __enable_defaulted_assignment_operators;
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ldionne wrote:

I think I would rather repeat the reference condition here and below. It avoids creating two names for the same thing, which then causes confusion when reading the non-defaulted `operator=` overloads in the code far below.

https://github.com/llvm/llvm-project/pull/89652