[libcxx-commits] [libcxx] [libcxx] Implement C++20 std::chrono::is_clock, std::chrono::is_clock_v (PR #160607)

[A. Jiang via libcxx-commits]

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@@ -0,0 +1,73 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___CHRONO_IS_CLOCK_H
+#define _LIBCPP___CHRONO_IS_CLOCK_H
+
+#include <__config>
+#include <__type_traits/integral_constant.h>
+#include <__type_traits/is_arithmetic.h>
+#include <__type_traits/is_same.h>
+#include <ratio>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+#if _LIBCPP_STD_VER >= 20
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+namespace chrono {
+
+template <class _Rep, class _Period>
+class duration;
+
+template <class _Clock, class _Duration>
+class time_point;
+
+// Helper to check that _Tp::time_point has the form time_point<_, typename _Tp::duration>.
+template <class _TimePoint, class _ClockType>
+constexpr bool __is_valid_clock_time_point_v = false;
+
+template <class _TimePointClock, class _ClockType>
+constexpr bool __is_valid_clock_time_point_v<time_point<_TimePointClock, typename _ClockType::duration>, _ClockType> =
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frederick-vs-ja wrote:

I think we no longer need `inline` here. GCC 15 has [CWG2387](https://cplusplus.github.io/CWG/issues/2387.html) implemented (see https://gcc.gnu.org/PR109126) (and Clang has implemented it long time ago), so `inline` doesn't have effect now.

https://github.com/llvm/llvm-project/pull/160607