1 files changed, 72 insertions, 0 deletions
diff --git a/libcxx/include/__chrono/is_clock.h b/libcxx/include/__chrono/is_clock.h
new file mode 100644
index 0000000..e63b848
--- /dev/null
+++ b/libcxx/include/__chrono/is_clock.h
@@ -0,0 +1,72 @@
+// -*- 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 <__chrono/duration.h>
+#include <__chrono/time_point.h>
+#include <__concepts/same_as.h>
+#include <__type_traits/integral_constant.h>
+#include <__type_traits/is_arithmetic.h>
+#include <__type_traits/is_class.h>
+#include <__type_traits/is_union.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 {
+
+// Helper to check that _Tp::time_point has the form time_point<_, typename _Tp::duration>.
+template <class _TimePoint, class _ClockType>
+inline constexpr bool __is_valid_clock_time_point_v = false;
+
+template <class _TimePointClock, class _ClockType>
+inline constexpr bool
+    __is_valid_clock_time_point_v<time_point<_TimePointClock, typename _ClockType::duration>, _ClockType> = true;
+
+// Check if a clock satisfies the Cpp17Clock requirements as defined in [time.clock.req]
+template <class _Tp>
+_LIBCPP_NO_SPECIALIZATIONS inline constexpr bool is_clock_v = requires {
+  typename _Tp::rep;
+  requires is_arithmetic_v<typename _Tp::rep> || is_class_v<typename _Tp::rep> || is_union_v<typename _Tp::rep>;
+
+  typename _Tp::period;
+  requires __is_ratio_v<typename _Tp::period>;
+
+  typename _Tp::duration;
+  requires same_as<typename _Tp::duration, duration<typename _Tp::rep, typename _Tp::period>>;
+
+  typename _Tp::time_point;
+  requires __is_valid_clock_time_point_v<typename _Tp::time_point, _Tp>;
+
+  _Tp::is_steady;
+  requires same_as<decltype((_Tp::is_steady)), const bool&>;
+
+  _Tp::now();
+  requires same_as<decltype(_Tp::now()), typename _Tp::time_point>;
+};
+
+template <class _Tp>
+struct _LIBCPP_NO_SPECIALIZATIONS is_clock : bool_constant<is_clock_v<_Tp>> {};
+
+} // namespace chrono
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_STD_VER
+#endif // _LIBCPP___CHRONO_IS_CLOCK_H