sfinae_change.patch

diff --git a/include/variant b/include/variant
index 6ecc193..8969790 100644
--- a/include/variant
+++ b/include/variant
@@ -1071,7 +1071,16 @@ using __best_match_t = typename result_of_t<__overload<_Types...>(_Tp&&)>::type;
 } // __variant_detail
 
 template <class... _Types>
-class _LIBCPP_TYPE_VIS_ONLY variant {
+class _LIBCPP_TYPE_VIS_ONLY variant :
+  private __sfinae_ctor_base<
+    __all<is_copy_constructible_v<_Types>...>::value,
+    __all<is_move_constructible_v<_Types>...>::value
+  >,
+  private __sfinae_assign_base<
+    __all<(is_copy_constructible_v<_Types> && is_move_constructible_v<_Types>
+           && is_copy_assignable_v<_Types>)...>::value,
+    __all<(is_move_constructible_v<_Types> && is_move_assignable_v<_Types>)...>::value
+  > {
   static_assert(0 < sizeof...(_Types),
                 "variant must consist of at least one alternative.");