[PATCH v2] libstdc++: use __is_enum built-in trait

[Ken Matsui via Gcc-patches]

This patch replaces is_enum<T>::value with __is_enum built-in trait in
the type_traits header.

libstdc++-v3/ChangeLog:

        * include/std/type_traits (__make_unsigned_selector): Use
        __is_enum built-in trait.
        (__make_signed_selector): Likewise.
        (__underlying_type_impl): Likewise.

Signed-off-by: Ken Matsui <kmat...@gcc.gnu.org>
---
 libstdc++-v3/include/std/type_traits | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/libstdc++-v3/include/std/type_traits 
b/libstdc++-v3/include/std/type_traits
index 0e7a9c9c7f3..9f086992ebc 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -1740,7 +1740,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   // Select between integral and enum: not possible to be both.
   template<typename _Tp,
           bool _IsInt = is_integral<_Tp>::value,
-          bool _IsEnum = is_enum<_Tp>::value>
+          bool _IsEnum = __is_enum(_Tp)>
     class __make_unsigned_selector;
 
   template<typename _Tp>
@@ -1900,7 +1900,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   // Select between integral and enum: not possible to be both.
   template<typename _Tp,
           bool _IsInt = is_integral<_Tp>::value,
-          bool _IsEnum = is_enum<_Tp>::value>
+          bool _IsEnum = __is_enum(_Tp)>
     class __make_signed_selector;
 
   template<typename _Tp>
@@ -2353,7 +2353,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     struct __common_type_fold<_CTp, _Rp, void>
     { };
 
-  template<typename _Tp, bool = is_enum<_Tp>::value>
+  template<typename _Tp, bool = __is_enum(_Tp)>
     struct __underlying_type_impl
     {
       using type = __underlying_type(_Tp);
-- 
2.41.0