Index: include/type_traits
===================================================================
--- include/type_traits
+++ include/type_traits
@@ -376,13 +376,9 @@
 template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_reference<_Tp&&> : public true_type {};
 #endif
 
-#if defined(__clang__) || (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
-#define _LIBCPP_HAS_TYPE_TRAITS
-#endif
-
 // is_union
 
-#if __has_feature(is_union) || (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
+#if __has_feature(is_union) || (_GNUC_VER >= 403)
 
 template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_union
     : public integral_constant<bool, __is_union(_Tp)> {};
@@ -397,7 +393,7 @@
 
 // is_class
 
-#if __has_feature(is_class) || (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
+#if __has_feature(is_class) || (_GNUC_VER >= 403)
 
 template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_class
     : public integral_constant<bool, __is_class(_Tp)> {};
@@ -484,7 +480,7 @@
 
 // is_enum
 
-#if __has_feature(is_enum) || (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
+#if __has_feature(is_enum) || (_GNUC_VER >= 403)
 
 template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_enum
     : public integral_constant<bool, __is_enum(_Tp)> {};
@@ -797,7 +793,7 @@
 struct _LIBCPP_TYPE_VIS_ONLY is_base_of
     : public integral_constant<bool, __is_base_of(_Bp, _Dp)> {};
 
-#else  // __has_feature(is_base_of)
+#else  // _LIBCPP_HAS_IS_BASE_OF
 
 namespace __is_base_of_imp
 {
@@ -822,7 +818,7 @@
     : public integral_constant<bool, is_class<_Bp>::value &&
                                      sizeof(__is_base_of_imp::__test<_Bp, _Dp>(0)) == 2> {};
 
-#endif  // __has_feature(is_base_of)
+#endif  // _LIBCPP_HAS_IS_BASE_OF
 
 // is_convertible
 
@@ -945,7 +941,7 @@
 
 // is_empty
 
-#if __has_feature(is_empty)
+#if __has_feature(is_empty) || (_GNUC_VER >= 407)
 
 template <class _Tp>
 struct _LIBCPP_TYPE_VIS_ONLY is_empty
@@ -996,17 +992,17 @@
 
 // has_virtual_destructor
 
-#if __has_feature(has_virtual_destructor) || (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
+#if __has_feature(has_virtual_destructor) || (_GNUC_VER >= 403)
 
 template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY has_virtual_destructor
     : public integral_constant<bool, __has_virtual_destructor(_Tp)> {};
 
-#else  // _LIBCPP_HAS_TYPE_TRAITS
+#else
 
 template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY has_virtual_destructor
     : public false_type {};
 
-#endif  // _LIBCPP_HAS_TYPE_TRAITS
+#endif
 
 // alignment_of
 
@@ -2434,7 +2430,7 @@
 
 template <class _Tp>
 struct _LIBCPP_TYPE_VIS_ONLY is_trivially_constructible<_Tp>
-#if __has_feature(has_trivial_constructor) || (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
+#if __has_feature(has_trivial_constructor) || (_GNUC_VER >= 403)
     : integral_constant<bool, __has_trivial_constructor(_Tp)>
 #else
     : integral_constant<bool, is_scalar<_Tp>::value>
@@ -2563,7 +2559,7 @@
 
 // is_trivially_assignable
 
-#if __has_feature(is_trivially_constructible)
+#if __has_feature(is_trivially_assignable)
 
 template <class _Tp, class _Arg>
 struct is_trivially_assignable
@@ -2571,7 +2567,7 @@
 {
 };
 
-#else  // !__has_feature(is_trivially_constructible)
+#else  // !__has_feature(is_trivially_assignable)
 
 template <class _Tp, class _Arg>
 struct is_trivially_assignable
@@ -2597,7 +2593,7 @@
 
 #endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
 
-#endif  // !__has_feature(is_trivially_constructible)
+#endif  // !__has_feature(is_trivially_assignable)
 
 // is_trivially_copy_assignable
 
@@ -2619,12 +2615,12 @@
 
 // is_trivially_destructible
 
-#if __has_feature(has_trivial_destructor) || (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
+#if __has_feature(has_trivial_destructor) || (_GNUC_VER >= 403)
 
 template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_trivially_destructible
     : public integral_constant<bool, __has_trivial_destructor(_Tp)> {};
 
-#else  // _LIBCPP_HAS_TYPE_TRAITS
+#else
 
 template <class _Tp> struct __libcpp_trivial_destructor
     : public integral_constant<bool, is_scalar<_Tp>::value ||
@@ -2633,7 +2629,7 @@
 template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_trivially_destructible
     : public __libcpp_trivial_destructor<typename remove_all_extents<_Tp>::type> {};
 
-#endif  // _LIBCPP_HAS_TYPE_TRAITS
+#endif
 
 // is_nothrow_constructible
 
@@ -2648,7 +2644,7 @@
 
 #ifndef _LIBCPP_HAS_NO_VARIADICS
 
-#if __has_feature(cxx_noexcept)
+#if __has_feature(cxx_noexcept) || (_GNUC_VER >= 407 && __cplusplus >= 201103L)
 
 template <bool, class _Tp, class... _Args> struct __libcpp_is_nothrow_constructible;
 
@@ -2686,7 +2682,7 @@
 
 template <class _Tp>
 struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_constructible<_Tp>
-#if __has_feature(has_nothrow_constructor) || (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
+#if __has_feature(has_nothrow_constructor) || (_GNUC_VER >= 403)
     : integral_constant<bool, __has_nothrow_constructor(_Tp)>
 #else
     : integral_constant<bool, is_scalar<_Tp>::value>
@@ -2700,7 +2696,7 @@
 #else
 struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_constructible<_Tp, _Tp>
 #endif
-#if __has_feature(has_nothrow_copy) || (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
+#if __has_feature(has_nothrow_copy) || (_GNUC_VER >= 403)
     : integral_constant<bool, __has_nothrow_copy(_Tp)>
 #else
     : integral_constant<bool, is_scalar<_Tp>::value>
@@ -2710,7 +2706,7 @@
 
 template <class _Tp>
 struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_constructible<_Tp, const _Tp&>
-#if __has_feature(has_nothrow_copy) || (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
+#if __has_feature(has_nothrow_copy) || (_GNUC_VER >= 403)
     : integral_constant<bool, __has_nothrow_copy(_Tp)>
 #else
     : integral_constant<bool, is_scalar<_Tp>::value>
@@ -2720,7 +2716,7 @@
 
 template <class _Tp>
 struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_constructible<_Tp, _Tp&>
-#if __has_feature(has_nothrow_copy) || (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
+#if __has_feature(has_nothrow_copy) || (_GNUC_VER >= 403)
     : integral_constant<bool, __has_nothrow_copy(_Tp)>
 #else
     : integral_constant<bool, is_scalar<_Tp>::value>
@@ -2742,7 +2738,7 @@
 template <class _Tp>
 struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_constructible<_Tp, __is_construct::__nat,
                                                        __is_construct::__nat>
-#if __has_feature(has_nothrow_constructor) || (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
+#if __has_feature(has_nothrow_constructor) || (_GNUC_VER >= 403)
     : integral_constant<bool, __has_nothrow_constructor(_Tp)>
 #else
     : integral_constant<bool, is_scalar<_Tp>::value>
@@ -2753,7 +2749,7 @@
 template <class _Tp>
 struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_constructible<_Tp, _Tp,
                                                        __is_construct::__nat>
-#if __has_feature(has_nothrow_copy) || (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
+#if __has_feature(has_nothrow_copy) || (_GNUC_VER >= 403)
     : integral_constant<bool, __has_nothrow_copy(_Tp)>
 #else
     : integral_constant<bool, is_scalar<_Tp>::value>
@@ -2764,7 +2760,7 @@
 template <class _Tp>
 struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_constructible<_Tp, const _Tp&,
                                                        __is_construct::__nat>
-#if __has_feature(has_nothrow_copy) || (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
+#if __has_feature(has_nothrow_copy) || (_GNUC_VER >= 403)
     : integral_constant<bool, __has_nothrow_copy(_Tp)>
 #else
     : integral_constant<bool, is_scalar<_Tp>::value>
@@ -2775,7 +2771,7 @@
 template <class _Tp>
 struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_constructible<_Tp, _Tp&,
                                                        __is_construct::__nat>
-#if __has_feature(has_nothrow_copy) || (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
+#if __has_feature(has_nothrow_copy) || (_GNUC_VER >= 403)
     : integral_constant<bool, __has_nothrow_copy(_Tp)>
 #else
     : integral_constant<bool, is_scalar<_Tp>::value>
@@ -2810,7 +2806,7 @@
 
 // is_nothrow_assignable
 
-#if __has_feature(cxx_noexcept)
+#if __has_feature(cxx_noexcept) || (_GNUC_VER >= 407 && __cplusplus >= 201103L)
 
 template <bool, class _Tp, class _Arg> struct __libcpp_is_nothrow_assignable;
 
@@ -2840,7 +2836,7 @@
 
 template <class _Tp>
 struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_assignable<_Tp&, _Tp>
-#if __has_feature(has_nothrow_assign) || (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
+#if __has_feature(has_nothrow_assign) || (_GNUC_VER >= 403)
     : integral_constant<bool, __has_nothrow_assign(_Tp)> {};
 #else
     : integral_constant<bool, is_scalar<_Tp>::value> {};
@@ -2848,7 +2844,7 @@
 
 template <class _Tp>
 struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_assignable<_Tp&, _Tp&>
-#if __has_feature(has_nothrow_assign) || (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
+#if __has_feature(has_nothrow_assign) || (_GNUC_VER >= 403)
     : integral_constant<bool, __has_nothrow_assign(_Tp)> {};
 #else
     : integral_constant<bool, is_scalar<_Tp>::value> {};
@@ -2856,7 +2852,7 @@
 
 template <class _Tp>
 struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_assignable<_Tp&, const _Tp&>
-#if __has_feature(has_nothrow_assign) || (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
+#if __has_feature(has_nothrow_assign) || (_GNUC_VER >= 403)
     : integral_constant<bool, __has_nothrow_assign(_Tp)> {};
 #else
     : integral_constant<bool, is_scalar<_Tp>::value> {};
@@ -2866,7 +2862,7 @@
 
 template <class _Tp>
 struct is_nothrow_assignable<_Tp&, _Tp&&>
-#if __has_feature(has_nothrow_assign) || (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
+#if __has_feature(has_nothrow_assign) || (_GNUC_VER >= 403)
     : integral_constant<bool, __has_nothrow_assign(_Tp)> {};
 #else
     : integral_constant<bool, is_scalar<_Tp>::value> {};
@@ -2896,7 +2892,7 @@
 
 // is_nothrow_destructible
 
-#if __has_feature(cxx_noexcept)
+#if __has_feature(cxx_noexcept) || (_GNUC_VER >= 407 && __cplusplus >= 201103L)
 
 template <bool, class _Tp> struct __libcpp_is_nothrow_destructible;
 
@@ -2953,12 +2949,12 @@
 
 // is_pod
 
-#if __has_feature(is_pod) || (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
+#if __has_feature(is_pod) || (_GNUC_VER >= 403)
 
 template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_pod
     : public integral_constant<bool, __is_pod(_Tp)> {};
 
-#else  // _LIBCPP_HAS_TYPE_TRAITS
+#else
 
 template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_pod
     : public integral_constant<bool, is_trivially_default_constructible<_Tp>::value   &&
@@ -2966,7 +2962,7 @@
                                      is_trivially_copy_assignable<_Tp>::value    &&
                                      is_trivially_destructible<_Tp>::value> {};
 
-#endif  // _LIBCPP_HAS_TYPE_TRAITS
+#endif
 
 // is_literal_type;
 
@@ -2982,7 +2978,7 @@
 // is_standard_layout;
 
 template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_standard_layout
-#if __has_feature(is_standard_layout)
+#if __has_feature(is_standard_layout) || (_GNUC_VER >= 407)
     : public integral_constant<bool, __is_standard_layout(_Tp)>
 #else
     : integral_constant<bool, is_scalar<typename remove_all_extents<_Tp>::type>::value>
@@ -3002,7 +2998,7 @@
 // is_trivial;
 
 template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_trivial
-#if __has_feature(is_trivial)
+#if __has_feature(is_trivial) || (_GNUC_VER >= 407)
     : public integral_constant<bool, __is_trivial(_Tp)>
 #else
     : integral_constant<bool, is_trivially_copyable<_Tp>::value &&
@@ -3332,7 +3328,7 @@
 {
 };
 
-#if __has_feature(cxx_noexcept)
+#if __has_feature(cxx_noexcept) || (_GNUC_VER >= 407 && __cplusplus >= 201103L)
 
 template <bool, class _Tp>
 struct __is_nothrow_swappable_imp