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[libcxx] Implement C++20 std::chrono::is_clock, std::chrono::is_clock_v
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‎libcxx/docs/ReleaseNotes/22.rst‎

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

‎libcxx/include/CMakeLists.txt‎

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@@ -262,6 +262,7 @@ set(files
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__chrono/gps_clock.h
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__chrono/hh_mm_ss.h
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__chrono/high_resolution_clock.h
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__chrono/is_clock.h
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__chrono/leap_second.h
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__chrono/literals.h
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__chrono/local_info.h

‎libcxx/include/__chrono/is_clock.h‎

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// -*- C++ -*-
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//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef _LIBCPP___CHRONO_IS_CLOCK_H
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#define _LIBCPP___CHRONO_IS_CLOCK_H
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#include <__config>
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#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
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# pragma GCC system_header
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#endif
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#if _LIBCPP_STD_VER >= 20
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# include <__type_traits/integral_constant.h>
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_LIBCPP_BEGIN_NAMESPACE_STD
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namespace chrono {
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template <class>
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struct is_clock : std::false_type {};
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template <class _Tp>
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requires requires {
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typename _Tp::rep;
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typename _Tp::period;
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typename _Tp::duration;
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typename _Tp::time_point;
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_Tp::is_steady;
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_Tp::now();
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}
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struct is_clock<_Tp> : std::true_type {};
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template <class _Tp>
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_LIBCPP_NO_SPECIALIZATIONS inline constexpr bool is_clock_v = is_clock<_Tp>::value;
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} // namespace chrono
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_LIBCPP_END_NAMESPACE_STD
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#endif // _LIBCPP_STD_VER
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#endif // _LIBCPP___CHRONO_IS_CLOCK_H

‎libcxx/include/chrono‎

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# include <__chrono/day.h>
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# include <__chrono/exception.h>
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# include <__chrono/hh_mm_ss.h>
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# include <__chrono/is_clock.h>
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# include <__chrono/literals.h>
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# include <__chrono/local_info.h>
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# include <__chrono/month.h>

‎libcxx/include/module.modulemap.in‎

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header "__chrono/high_resolution_clock.h"
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export *
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}
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module is_clock {
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header "__chrono/is_clock.h"
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export std_core.type_traits.integral_constant
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}
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module leap_second {
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header "__chrono/leap_second.h"
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}

‎libcxx/modules/std/chrono.inc‎

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using std::chrono::duration_values;
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// using std::chrono::is_clock;
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// using std::chrono::is_clock_v;
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using std::chrono::is_clock;
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using std::chrono::is_clock_v;
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// [time.duration.nonmember], duration arithmetic
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using std::chrono::operator+;

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

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//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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// REQUIRES: std-at-least-c++20
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#include <chrono>
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#include <ratio>
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struct EmptyStruct {};
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// Test structs missing required members
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struct MissingRep {
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using period = std::ratio<1>;
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using duration = std::chrono::seconds;
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using time_point = std::chrono::time_point<MissingRep>;
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static constexpr bool is_steady = false;
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static time_point now();
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};
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struct MissingPeriod {
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using rep = long;
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using duration = std::chrono::seconds;
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using time_point = std::chrono::time_point<MissingPeriod>;
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static constexpr bool is_steady = false;
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static time_point now();
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};
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struct MissingDuration {
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using rep = long;
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using time_point = long;
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static constexpr bool is_steady = false;
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static time_point now();
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};
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struct MissingTimePoint {
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using rep = long;
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using period = std::ratio<1>;
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using duration = std::chrono::seconds;
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static constexpr bool is_steady = false;
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static std::chrono::time_point<MissingTimePoint> now();
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};
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struct MissingIsSteady {
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using rep = long;
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using period = std::ratio<1>;
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using duration = std::chrono::seconds;
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using time_point = std::chrono::time_point<MissingIsSteady>;
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static time_point now();
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};
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struct MissingNow {
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using rep = long;
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using period = std::ratio<1>;
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using duration = std::chrono::seconds;
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using time_point = std::chrono::time_point<MissingNow>;
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static constexpr bool is_steady = false;
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};
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// Valid clock types
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struct ValidSteadyClock {
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using rep = long long;
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using period = std::nano;
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using duration = std::chrono::nanoseconds;
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using time_point = std::chrono::time_point<ValidSteadyClock>;
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static constexpr bool is_steady = true;
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static time_point now();
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};
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struct ValidSystemClock {
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using rep = int64_t;
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using period = std::micro;
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using duration = std::chrono::microseconds;
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using time_point = std::chrono::time_point<ValidSystemClock>;
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static constexpr bool is_steady = false;
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static time_point now();
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};
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int main(int, char**) {
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// Test both is_clock and is_clock_v
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static_assert(std::chrono::is_clock<std::chrono::system_clock>::value);
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static_assert(std::chrono::is_clock_v<std::chrono::system_clock>);
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// Test standard clock types
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static_assert(std::chrono::is_clock_v<std::chrono::system_clock>);
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static_assert(std::chrono::is_clock_v<std::chrono::steady_clock>);
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static_assert(std::chrono::is_clock_v<std::chrono::high_resolution_clock>);
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// Test non-clock types
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static_assert(!std::chrono::is_clock_v<EmptyStruct>);
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static_assert(!std::chrono::is_clock_v<int>);
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static_assert(!std::chrono::is_clock_v<void>);
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static_assert(!std::chrono::is_clock_v<std::chrono::system_clock::time_point>);
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static_assert(!std::chrono::is_clock_v<std::chrono::steady_clock::time_point>);
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static_assert(!std::chrono::is_clock_v<std::chrono::seconds>);
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static_assert(!std::chrono::is_clock_v<std::chrono::milliseconds>);
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// Test structs missing required members
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static_assert(!std::chrono::is_clock_v<MissingRep>);
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static_assert(!std::chrono::is_clock_v<MissingPeriod>);
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static_assert(!std::chrono::is_clock_v<MissingDuration>);
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static_assert(!std::chrono::is_clock_v<MissingTimePoint>);
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static_assert(!std::chrono::is_clock_v<MissingIsSteady>);
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static_assert(!std::chrono::is_clock_v<MissingNow>);
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// Test valid custom clocks
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static_assert(std::chrono::is_clock_v<ValidSteadyClock>);
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static_assert(std::chrono::is_clock_v<ValidSystemClock>);
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// cv-qualified and reference types
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static_assert(std::chrono::is_clock_v<const std::chrono::system_clock>);
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static_assert(std::chrono::is_clock_v<volatile std::chrono::system_clock>);
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static_assert(std::chrono::is_clock_v<const volatile std::chrono::system_clock>);
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static_assert(!std::chrono::is_clock_v<std::chrono::system_clock&>);
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static_assert(!std::chrono::is_clock_v<std::chrono::system_clock&&>);
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static_assert(!std::chrono::is_clock_v<const std::chrono::system_clock&>);
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// array and pointer types
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static_assert(!std::chrono::is_clock_v<std::chrono::system_clock[]>);
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static_assert(!std::chrono::is_clock_v<std::chrono::system_clock[10]>);
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static_assert(!std::chrono::is_clock_v<std::chrono::system_clock*>);
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static_assert(!std::chrono::is_clock_v<std::chrono::system_clock* const>);
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return 0;
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}

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