From ef2afa1e83fad5f813e5d12f4a88acbaf8cf85fe Mon Sep 17 00:00:00 2001
From: Nikolas Klauser <nikolasklauser@berlin.de>
Date: Mon, 6 Jan 2025 12:12:40 +0100
Subject: [PATCH] [libc++] Simplify unwrap_ref_decay a bit (#121623)

---
 libcxx/include/__type_traits/unwrap_ref.h | 15 ++++-----------
 libcxx/include/__utility/pair.h           |  6 ++----
 libcxx/include/tuple                      |  4 ++--
 3 files changed, 8 insertions(+), 17 deletions(-)

diff --git a/libcxx/include/__type_traits/unwrap_ref.h b/libcxx/include/__type_traits/unwrap_ref.h
index 74c4fde915c3..5ac037333d08 100644
--- a/libcxx/include/__type_traits/unwrap_ref.h
+++ b/libcxx/include/__type_traits/unwrap_ref.h
@@ -29,6 +29,9 @@ struct __unwrap_reference<reference_wrapper<_Tp> > {
   using type _LIBCPP_NODEBUG = _Tp&;
 };
 
+template <class _Tp>
+using __unwrap_ref_decay_t = typename __unwrap_reference<__decay_t<_Tp> >::type;
+
 #if _LIBCPP_STD_VER >= 20
 template <class _Tp>
 struct unwrap_reference : __unwrap_reference<_Tp> {};
@@ -40,19 +43,9 @@ template <class _Tp>
 struct unwrap_ref_decay : unwrap_reference<__decay_t<_Tp> > {};
 
 template <class _Tp>
-using unwrap_ref_decay_t = typename unwrap_ref_decay<_Tp>::type;
+using unwrap_ref_decay_t = __unwrap_ref_decay_t<_Tp>;
 #endif // _LIBCPP_STD_VER >= 20
 
-template <class _Tp>
-struct __unwrap_ref_decay
-#if _LIBCPP_STD_VER >= 20
-    : unwrap_ref_decay<_Tp>
-#else
-    : __unwrap_reference<__decay_t<_Tp> >
-#endif
-{
-};
-
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___TYPE_TRAITS_UNWRAP_REF_H
diff --git a/libcxx/include/__utility/pair.h b/libcxx/include/__utility/pair.h
index f9d0f4e47231..bb81e30926d7 100644
--- a/libcxx/include/__utility/pair.h
+++ b/libcxx/include/__utility/pair.h
@@ -532,11 +532,9 @@ swap(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y) noexcept(noexcept(__x
 #endif
 
 template <class _T1, class _T2>
-inline _LIBCPP_HIDE_FROM_ABI
-_LIBCPP_CONSTEXPR_SINCE_CXX14 pair<typename __unwrap_ref_decay<_T1>::type, typename __unwrap_ref_decay<_T2>::type>
+inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<__unwrap_ref_decay_t<_T1>, __unwrap_ref_decay_t<_T2> >
 make_pair(_T1&& __t1, _T2&& __t2) {
-  return pair<typename __unwrap_ref_decay<_T1>::type, typename __unwrap_ref_decay<_T2>::type>(
-      std::forward<_T1>(__t1), std::forward<_T2>(__t2));
+  return pair<__unwrap_ref_decay_t<_T1>, __unwrap_ref_decay_t<_T2> >(std::forward<_T1>(__t1), std::forward<_T2>(__t2));
 }
 
 template <class _T1, class _T2>
diff --git a/libcxx/include/tuple b/libcxx/include/tuple
index b2478746f5e2..e4f1fc209b73 100644
--- a/libcxx/include/tuple
+++ b/libcxx/include/tuple
@@ -1125,9 +1125,9 @@ inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 tuple<_Tp&...> tie(_T
 }
 
 template <class... _Tp>
-inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 tuple<typename __unwrap_ref_decay<_Tp>::type...>
+inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 tuple<__unwrap_ref_decay_t<_Tp>...>
 make_tuple(_Tp&&... __t) {
-  return tuple<typename __unwrap_ref_decay<_Tp>::type...>(std::forward<_Tp>(__t)...);
+  return tuple<__unwrap_ref_decay_t<_Tp>...>(std::forward<_Tp>(__t)...);
 }
 
 template <class... _Tp>