address comments

Author: yuxuanchen1997

libcxx/docs/ReleaseNotes/22.rst

@@ -41,8 +41,6 @@ Implemented Papers
 - P2321R2: ``zip`` (`Github <https://llvm.org/PR105169>`__) (The paper is partially implemented. ``zip_transform_view``
   is implemented in this release)
 - P3168R2: Give ``std::optional`` Range Support (`Github <https://llvm.org/PR105430>`__)
-- P0355R7: ``std::chrono::is_clock`` and ``std::chrono::is_clock_v`` (`Github <https://llvm.org/PR160607>` __)
-  (The paper is partially implemented. ``is_clock`` and ``is_clock_v`` is implemented in this release)
 
 Improvements and New Features
 -----------------------------

libcxx/include/__chrono/is_clock.h

@@ -11,15 +11,14 @@
 #define _LIBCPP___CHRONO_IS_CLOCK_H
 
 #include <__config>
+#include <__type_traits/integral_constant.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 #if _LIBCPP_STD_VER >= 20
 
-#  include <__type_traits/integral_constant.h>
-
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 namespace chrono {

libcxx/include/chrono

@@ -218,6 +218,9 @@ template <class ToDuration, class Rep, class Period>
 template <class ToDuration, class Rep, class Period>
     constexpr ToDuration round(const duration<Rep, Period>& d);    // C++17
 
+template <class T> struct is_clock;                                // C++20
+template <class T> inline constexpr bool is_clock_v = is_clock<T>::value;                   // C++20
+
 // duration I/O
 template<class charT, class traits, class Rep, class Period>       // C++20
   basic_ostream<charT, traits>&

libcxx/test/std/time/time.traits.is.clock/trait.is.clock.pass.cpp renamed to libcxx/test/std/time/time.traits.is.clock/trait.is.clock.compile.pass.cpp

@@ -0,0 +1,22 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: std-at-least-c++20
+
+#include <chrono>
+#include <ratio>
+
+namespace std::chrono {
+// try adding specializations to is_clock
+template <>
+struct is_clock<int> : std::false_type {}; // expected-error@*:* {{'is_clock' cannot be specialized}}
+
+template <>
+constexpr bool is_clock_v<float> = false; // expected-error@*:* {{'is_clock_v' cannot be specialized}}
+
+}