[libc++] Simplify the implementation of is_null_pointer a bit

[philnik777]

No description provided.

[llvmbot]

@llvm/pr-subscribers-libcxx

Author: Nikolas Klauser (philnik777)

Changes

---

Full diff: https://github.com/llvm/llvm-project/pull/98728.diff

3 Files Affected:

• (modified) libcxx/include/__type_traits/is_fundamental.h (+1-1)
• (modified) libcxx/include/__type_traits/is_null_pointer.h (+3-9)
• (modified) libcxx/include/__type_traits/is_scalar.h (+1-1)

diff --git a/libcxx/include/__type_traits/is_fundamental.h b/libcxx/include/__type_traits/is_fundamental.h
index 57206e0d9deb1..55f8e41f75f45 100644
--- a/libcxx/include/__type_traits/is_fundamental.h
+++ b/libcxx/include/__type_traits/is_fundamental.h
@@ -34,7 +34,7 @@ inline constexpr bool is_fundamental_v = __is_fundamental(_Tp);
 
 template <class _Tp>
 struct _LIBCPP_TEMPLATE_VIS is_fundamental
-    : public integral_constant<bool, is_void<_Tp>::value || __is_nullptr_t<_Tp>::value || is_arithmetic<_Tp>::value> {};
+    : public integral_constant<bool, is_void<_Tp>::value || __is_null_pointer_v<_Tp> || is_arithmetic<_Tp>::value> {};
 
 #  if _LIBCPP_STD_VER >= 17
 template <class _Tp>
diff --git a/libcxx/include/__type_traits/is_null_pointer.h b/libcxx/include/__type_traits/is_null_pointer.h
index c666f5f24759c..9f5697e232684 100644
--- a/libcxx/include/__type_traits/is_null_pointer.h
+++ b/libcxx/include/__type_traits/is_null_pointer.h
@@ -11,7 +11,6 @@
 
 #include <__config>
 #include <__type_traits/integral_constant.h>
-#include <__type_traits/remove_cv.h>
 #include <cstddef>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
@@ -21,20 +20,15 @@
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 template <class _Tp>
-struct __is_nullptr_t_impl : public false_type {};
-template <>
-struct __is_nullptr_t_impl<nullptr_t> : public true_type {};
-
-template <class _Tp>
-struct _LIBCPP_TEMPLATE_VIS __is_nullptr_t : public __is_nullptr_t_impl<__remove_cv_t<_Tp> > {};
+inline const bool __is_null_pointer_v = __is_same(__remove_cv(_Tp), nullptr_t);
 
 #if _LIBCPP_STD_VER >= 14
 template <class _Tp>
-struct _LIBCPP_TEMPLATE_VIS is_null_pointer : public __is_nullptr_t_impl<__remove_cv_t<_Tp> > {};
+struct _LIBCPP_TEMPLATE_VIS is_null_pointer : integral_constant<bool, __is_null_pointer_v<_Tp>> {};
 
 #  if _LIBCPP_STD_VER >= 17
 template <class _Tp>
-inline constexpr bool is_null_pointer_v = is_null_pointer<_Tp>::value;
+inline constexpr bool is_null_pointer_v = __is_null_pointer_v<_Tp>;
 #  endif
 #endif // _LIBCPP_STD_VER >= 14
 
diff --git a/libcxx/include/__type_traits/is_scalar.h b/libcxx/include/__type_traits/is_scalar.h
index 15f1c71554f22..455200de47208 100644
--- a/libcxx/include/__type_traits/is_scalar.h
+++ b/libcxx/include/__type_traits/is_scalar.h
@@ -49,7 +49,7 @@ struct _LIBCPP_TEMPLATE_VIS is_scalar
           bool, is_arithmetic<_Tp>::value ||
                 is_member_pointer<_Tp>::value ||
                 is_pointer<_Tp>::value ||
-                __is_nullptr_t<_Tp>::value ||
+                __is_null_pointer_v<_Tp> ||
                 __is_block<_Tp>::value ||
                 is_enum<_Tp>::value> {};
 // clang-format on

[ldionne]

I would drop NFC from the commit when merging, though. It's not intended to change anything, but it's also not a change to e.g. a comment.