[libcxx-commits] [libcxx] [libc++] Add __simple_tuple and replace a bunch of uses of tuple with it (PR #214566)

[via libcxx-commits]

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@@ -0,0 +1,108 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___TUPLE_SIMPLE_TUPLE_H
+#define _LIBCPP___TUPLE_SIMPLE_TUPLE_H
+
+#include <__config>
+#include <__cstddef/size_t.h>
+#include <__type_traits/conditional.h>
+#include <__type_traits/copy_cvref.h>
+#include <__type_traits/disjunction.h>
+#include <__type_traits/enable_if.h>
+#include <__type_traits/integral_constant.h>
+#include <__type_traits/invoke.h>
+#include <__type_traits/is_empty.h>
+#include <__type_traits/is_final.h>
+#include <__type_traits/is_reference.h>
+#include <__type_traits/is_same.h>
+#include <__type_traits/remove_cvref.h>
+#include <__utility/forward.h>
+#include <__utility/integer_sequence.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+#ifndef _LIBCPP_CXX03_LANG
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template <size_t, class _Tp, bool = is_empty<_Tp>::value && !__is_final_v<_Tp>>
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higher-performance wrote:

Why do you need `is_empty` and `__is_final_v` if all you're doing is storing the type as a field instead of inheriting from it?

https://github.com/llvm/llvm-project/pull/214566