1 files changed, 93 insertions, 0 deletions
diff --git a/libcxx/include/__tuple_dir/tuple_element.h b/libcxx/include/__tuple_dir/tuple_element.h
new file mode 100644
index 000000000000..06f49bf500fb
--- /dev/null
+++ b/libcxx/include/__tuple_dir/tuple_element.h
@@ -0,0 +1,93 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_TUPLE_ELEMENT_H
+#define _LIBCPP___TUPLE_TUPLE_ELEMENT_H
+
+#include <__config>
+#include <__tuple_dir/tuple_indices.h>
+#include <__tuple_dir/tuple_types.h>
+#include <__type_traits/add_const.h>
+#include <__type_traits/add_cv.h>
+#include <__type_traits/add_volatile.h>
+#include <cstddef>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template <size_t _Ip, class _Tp> struct _LIBCPP_TEMPLATE_VIS tuple_element;
+
+template <size_t _Ip, class _Tp>
+struct _LIBCPP_TEMPLATE_VIS tuple_element<_Ip, const _Tp>
+{
+    typedef _LIBCPP_NODEBUG typename add_const<typename tuple_element<_Ip, _Tp>::type>::type type;
+};
+
+template <size_t _Ip, class _Tp>
+struct _LIBCPP_TEMPLATE_VIS tuple_element<_Ip, volatile _Tp>
+{
+    typedef _LIBCPP_NODEBUG typename add_volatile<typename tuple_element<_Ip, _Tp>::type>::type type;
+};
+
+template <size_t _Ip, class _Tp>
+struct _LIBCPP_TEMPLATE_VIS tuple_element<_Ip, const volatile _Tp>
+{
+    typedef _LIBCPP_NODEBUG typename add_cv<typename tuple_element<_Ip, _Tp>::type>::type type;
+};
+
+#ifndef _LIBCPP_CXX03_LANG
+
+#if !__has_builtin(__type_pack_element)
+
+namespace __indexer_detail {
+
+template <size_t _Idx, class _Tp>
+struct __indexed { using type _LIBCPP_NODEBUG = _Tp; };
+
+template <class _Types, class _Indexes> struct __indexer;
+
+template <class ..._Types, size_t ..._Idx>
+struct __indexer<__tuple_types<_Types...>, __tuple_indices<_Idx...>>
+    : __indexed<_Idx, _Types>...
+{};
+
+template <size_t _Idx, class _Tp>
+__indexed<_Idx, _Tp> __at_index(__indexed<_Idx, _Tp> const&);
+
+} // namespace __indexer_detail
+
+template <size_t _Idx, class ..._Types>
+using __type_pack_element _LIBCPP_NODEBUG = typename decltype(
+    __indexer_detail::__at_index<_Idx>(
+        __indexer_detail::__indexer<
+            __tuple_types<_Types...>,
+            typename __make_tuple_indices<sizeof...(_Types)>::type
+        >{})
+  )::type;
+#endif
+
+template <size_t _Ip, class ..._Types>
+struct _LIBCPP_TEMPLATE_VIS tuple_element<_Ip, __tuple_types<_Types...> >
+{
+    static_assert(_Ip < sizeof...(_Types), "tuple_element index out of range");
+    typedef _LIBCPP_NODEBUG __type_pack_element<_Ip, _Types...> type;
+};
+
+#if _LIBCPP_STD_VER > 11
+template <size_t _Ip, class ..._Tp>
+using tuple_element_t _LIBCPP_NODEBUG = typename tuple_element <_Ip, _Tp...>::type;
+#endif
+
+#endif // _LIBCPP_CXX03_LANG
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___TUPLE_TUPLE_ELEMENT_H