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Perform stricter checks in chrono::is_clock_v #5892

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Merged
merged 13 commits into from
Nov 27, 2025
+285 −69
Merged

Perform stricter checks in chrono::is_clock_v #5892

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38a8100
Add tests
vmichal Nov 21, 2025
68b732c
Perform additional (stricter) checks in std::chrono::is_clock_v
vmichal Nov 21, 2025
8417029
Replace _Clock::now() with _Clock::now to reject typedefs
vmichal Nov 21, 2025
aeeea02
Replace links in comments with proper reference to the standard
vmichal Nov 21, 2025
290c5eb
Correct endline character
vmichal Nov 21, 2025
a14115e
`T::now()` is part of the basic checks.
StephanTLavavej Nov 25, 2025
f4de01a
Remove unnecessary newlines.
StephanTLavavej Nov 25, 2025
6266357
Use terse `static_assert` in C++20.
StephanTLavavej Nov 25, 2025
e9b070d
Include `<ratio>`.
StephanTLavavej Nov 25, 2025
dce37e0
`constexpr static` => `static constexpr`
StephanTLavavej Nov 25, 2025
960d51c
`is_steady_member` => `is_steady_not_static`
StephanTLavavej Nov 25, 2025
e350ce8
Add `time_point_wrong_type3`, `is_steady_wrong_type`.
StephanTLavavej Nov 25, 2025
c5ba2a8
Reported VSO-2649325 "C1XX incorrectly handles `requires { C::now(); …
StephanTLavavej Nov 25, 2025
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22 changes: 18 additions & 4 deletions stl/inc/__msvc_chrono.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -58,15 +58,32 @@ namespace chrono {
}
};

_EXPORT_STD template <class _Rep, class _Period = ratio<1>>
class duration;

_EXPORT_STD template <class _Clock, class _Duration = typename _Clock::duration>
class time_point;

#if _HAS_CXX20
_EXPORT_STD template <class _Clock>
_NO_SPECIALIZATIONS_OF_VARIABLE_TEMPLATES constexpr bool is_clock_v = requires {
// Basic checks from N5014 [time.traits.is.clock]/1
typename _Clock::rep;
typename _Clock::period;
typename _Clock::duration;
typename _Clock::time_point;
_Clock::is_steady;
_Clock::now();

// Additional stricter checks from N5014 [time.clock.req]/2
// "An arithmetic type or a class emulating an arithmetic type" is not checked
requires _Is_ratio_v<typename _Clock::period>;
requires same_as<typename _Clock::duration, duration<typename _Clock::rep, typename _Clock::period>>;
requires same_as<typename _Clock::time_point, time_point<_Clock>>
|| same_as<typename _Clock::time_point,
time_point<typename _Clock::time_point::clock, typename _Clock::duration>>;
{ _Clock::is_steady } -> std::same_as<const bool&>;
{ _Clock::now() } -> std::same_as<typename _Clock::time_point>;
};
_EXPORT_STD template <class _Clock>
struct _NO_SPECIALIZATIONS_CITING("N5014 [time.traits.is.clock]/2") is_clock : bool_constant<is_clock_v<_Clock>> {};
Expand All @@ -84,9 +101,6 @@ namespace chrono {
true;
#endif // ^^^ !_HAS_CXX20 ^^^

_EXPORT_STD template <class _Rep, class _Period = ratio<1>>
class duration;

template <class _Ty>
constexpr bool _Is_duration_v = _Is_specialization_v<_Ty, duration>;

Expand Down Expand Up @@ -203,7 +217,7 @@ namespace chrono {
_Rep _MyRep; // the stored rep
};

_EXPORT_STD template <class _Clock, class _Duration = typename _Clock::duration>
_EXPORT_STD template <class _Clock, class _Duration>
class time_point { // represents a point in time
public:
using clock = _Clock;
Expand Down
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