Implement P0550R2: Transformation Trait remove_cvref

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@318011 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 14 insertions, 0 deletions

diff --git a/include/type_traits b/include/type_traits
index 6c111abfd..1dd50b82f 100644
--- a/include/type_traits
+++ b/include/type_traits
@@ -150,6 +150,7 @@ namespace std
     template <size_t Len, size_t Align = most_stringent_alignment_requirement>
         struct aligned_storage;
     template <size_t Len, class... Types> struct aligned_union;
+    template <class T> struct remove_cvref; // C++20
 
     template <class T> struct decay;
     template <class... T> struct common_type;
@@ -203,6 +204,8 @@ namespace std
     template <std::size_t Len, class... Types>
       using aligned_union_t   = typename aligned_union<Len,Types...>::type;  // C++14
     template <class T>
+      using remove_cvref_t    = typename remove_cvref<T>::type;  // C++20
+    template <class T>
       using decay_t           = typename decay<T>::type;  // C++14
     template <bool b, class T=void>
       using enable_if_t       = typename enable_if<b,T>::type;  // C++14
@@ -1141,6 +1144,17 @@ template <class _Tp, class _Up>
 struct __is_same_uncvref : is_same<typename __uncvref<_Tp>::type,
                                    typename __uncvref<_Up>::type> {};
 
+#if _LIBCPP_STD_VER > 17
+// aligned_union - same as __uncvref
+template <class _Tp>
+struct remove_cvref {
+    using type = remove_cv_t<remove_reference_t<_Tp>>;
+};
+
+template <class _Tp> using remove_cvref_t = typename remove_cvref<_Tp>::type;
+#endif
+
+
 struct __any
 {
     __any(...);