[gcc(refs/users/kmatsui/heads/is_array)] libstdc++: use new built-in trait __is_array

[gcc(refs/users/kmatsui/heads/is_array)] libstdc++: use new built-in trait __is_array

[Ken Matsui]

https://gcc.gnu.org/g:1245a9e56d9736bcb3250cec9de648d386d1fde8

commit 1245a9e56d9736bcb3250cec9de648d386d1fde8
Author: Ken Matsui <kmatsui@gcc.gnu.org>
Date:   Tue Mar 21 08:57:14 2023 -0700

    libstdc++: use new built-in trait __is_array
    
    This patch lets libstdc++ use new built-in trait __is_array.
    
    libstdc++-v3/ChangeLog:
    
            * include/std/type_traits (is_array): Use __is_array built-in trait.
            (is_array_v): Likewise.
    
    Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>

Diff:
---
 libstdc++-v3/include/std/type_traits | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
index 0e7a9c9c7f3..f2a3a327e7d 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -503,6 +503,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     { };
 
   /// is_array
+#if __has_builtin(__is_array)
+  template<typename _Tp>
+    struct is_array
+    : public __bool_constant<__is_array(_Tp)>
+    { };
+#else
   template<typename>
     struct is_array
     : public false_type { };
@@ -514,6 +520,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   template<typename _Tp>
     struct is_array<_Tp[]>
     : public true_type { };
+#endif
 
   template<typename>
     struct __is_pointer_helper
@@ -3161,12 +3168,17 @@ template <typename _Tp>
 template <typename _Tp>
   inline constexpr bool is_floating_point_v = is_floating_point<_Tp>::value;
 
+#if __has_builtin(__is_array)
+template <typename _Tp>
+  inline constexpr bool is_array_v = __is_array(_Tp);
+#else
 template <typename _Tp>
   inline constexpr bool is_array_v = false;
 template <typename _Tp>
   inline constexpr bool is_array_v<_Tp[]> = true;
 template <typename _Tp, size_t _Num>
   inline constexpr bool is_array_v<_Tp[_Num]> = true;
+#endif
 
 template <typename _Tp>
   inline constexpr bool is_pointer_v = is_pointer<_Tp>::value;