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<chrono>: Overhaul zoned_time to use concepts instead of SFINAE #5907

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<chrono>: Overhaul zoned_time to use concepts instead of SFINAE #5907

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c70faa8
Move ref within `type_identity_t` for consistency.
StephanTLavavej Nov 24, 2025
30d3398
zoned_time overhaul: Convert SFINAE to concepts.
StephanTLavavej Nov 24, 2025
58d2abc
zoned_time: Avoid delegating constructors.
StephanTLavavej Nov 24, 2025
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104 changes: 53 additions & 51 deletions stl/inc/chrono
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Original file line number Diff line number Diff line change
Expand Up @@ -2460,86 +2460,88 @@ namespace chrono {
public:
using duration = common_type_t<_Duration, seconds>;

template <class _Traits2 = _Traits, class = void_t<decltype(_Traits2::default_zone())>>
zoned_time() : _Zone{_Traits::default_zone()} {}
zoned_time()
requires requires { _Traits::default_zone(); }
: _Zone{_Traits::default_zone()} {}

zoned_time(const zoned_time&) = default;
zoned_time& operator=(const zoned_time&) = default;

template <class _Traits2 = _Traits, class = void_t<decltype(_Traits2::default_zone())>>
zoned_time(const sys_time<_Duration>& _Sys) : _Zone{_Traits::default_zone()}, _Tp{_Sys} {}
zoned_time(const sys_time<_Duration>& _Sys)
requires requires { _Traits::default_zone(); }
: _Zone{_Traits::default_zone()}, _Tp{_Sys} {}

explicit zoned_time(_TimeZonePtr _Tz) noexcept /* strengthened */ : _Zone{_STD move(_Tz)} {}

template <class _Traits2 = _Traits,
enable_if_t<is_constructible_v<zoned_time, decltype(_Traits2::locate_zone(string_view{}))>, int> = 0>
explicit zoned_time(string_view _Name) : _Zone{_Traits::locate_zone(_Name)} {}
explicit zoned_time(string_view _Name)
requires requires {
{ _Traits::locate_zone(_Name) } -> convertible_to<_TimeZonePtr>;
}
: _Zone{_Traits::locate_zone(_Name)} {}

template <class _Duration2, enable_if_t<is_convertible_v<sys_time<_Duration2>, sys_time<_Duration>>, int> = 0>
template <class _Duration2>
requires is_convertible_v<sys_time<_Duration2>, sys_time<_Duration>>
zoned_time(const zoned_time<_Duration2, _TimeZonePtr>& _Zt) noexcept /* strengthened */
: _Zone{_Zt.get_time_zone()}, _Tp{_Zt.get_sys_time()} {}

zoned_time(_TimeZonePtr _Tz, const sys_time<_Duration>& _Sys) : _Zone{_STD move(_Tz)}, _Tp{_Sys} {}

template <class _Traits2 = _Traits,
enable_if_t<is_constructible_v<zoned_time, decltype(_Traits2::locate_zone(string_view{})),
const sys_time<_Duration>&>,
int> = 0>
zoned_time(string_view _Name, type_identity_t<const sys_time<_Duration>&> _Sys)
: zoned_time{_Traits::locate_zone(_Name), _Sys} {}
requires requires {
{ _Traits::locate_zone(_Name) } -> convertible_to<_TimeZonePtr>;
}
: _Zone{_Traits::locate_zone(_Name)}, _Tp{_Sys} {}

template <class _Ptr = _TimeZonePtr,
enable_if_t<
is_convertible_v<decltype(_STD declval<_Ptr&>()->to_sys(local_time<_Duration>{})), sys_time<duration>>,
int> = 0>
zoned_time(_TimeZonePtr _Tz, const local_time<_Duration>& _Local)
requires requires {
{ _Tz->to_sys(_Local) } -> convertible_to<sys_time<duration>>;
}
: _Zone{_STD move(_Tz)}, _Tp{_Zone->to_sys(_Local)} {}

template <class _Traits2 = _Traits,
enable_if_t<is_constructible_v<zoned_time, decltype(_Traits2::locate_zone(string_view{})),
const local_time<_Duration>&>,
int> = 0>
zoned_time(string_view _Name, type_identity_t<const local_time<_Duration>>& _Local)
: zoned_time{_Traits::locate_zone(_Name), _Local} {}

template <class _Ptr = _TimeZonePtr,
enable_if_t<
is_convertible_v<decltype(_STD declval<_Ptr&>()->to_sys(local_time<_Duration>{}, choose::earliest)),
sys_time<duration>>,
int> = 0>
zoned_time(string_view _Name, type_identity_t<const local_time<_Duration>&> _Local)
requires requires {
{ _Traits::locate_zone(_Name) } -> convertible_to<_TimeZonePtr>;
{ _STD declval<_TimeZonePtr&>() -> to_sys(_Local) } -> convertible_to<sys_time<duration>>;
}
: _Zone{_Traits::locate_zone(_Name)}, _Tp{_Zone->to_sys(_Local)} {}

zoned_time(_TimeZonePtr _Tz, const local_time<_Duration>& _Local, choose _Choose)
requires requires {
{ _Tz->to_sys(_Local, _Choose) } -> convertible_to<sys_time<duration>>;
}
: _Zone{_STD move(_Tz)}, _Tp{_Zone->to_sys(_Local, _Choose)} {}

template <class _Traits2 = _Traits,
enable_if_t<is_constructible_v<zoned_time, decltype(_Traits2::locate_zone(string_view{})),
const local_time<_Duration>&, choose>,
int> = 0>
zoned_time(string_view _Name, type_identity_t<const local_time<_Duration>&> _Local, choose _Choose)
: zoned_time{_Traits::locate_zone(_Name), _Local, _Choose} {}
requires requires {
{ _Traits::locate_zone(_Name) } -> convertible_to<_TimeZonePtr>;
{ _STD declval<_TimeZonePtr&>() -> to_sys(_Local, _Choose) } -> convertible_to<sys_time<duration>>;
}
: _Zone{_Traits::locate_zone(_Name)}, _Tp{_Zone->to_sys(_Local, _Choose)} {}

template <class _Duration2, class _TimeZonePtr2,
enable_if_t<is_convertible_v<sys_time<_Duration2>, sys_time<_Duration>>, int> = 0>
template <class _Duration2, class _TimeZonePtr2>
requires is_convertible_v<sys_time<_Duration2>, sys_time<_Duration>>
zoned_time(_TimeZonePtr _Tz, const zoned_time<_Duration2, _TimeZonePtr2>& _Zt) noexcept /* strengthened */
: _Zone{_STD move(_Tz)}, _Tp{_Zt.get_sys_time()} {}

template <class _Duration2, class _TimeZonePtr2,
enable_if_t<is_convertible_v<sys_time<_Duration2>, sys_time<_Duration>>, int> = 0>
template <class _Duration2, class _TimeZonePtr2>
requires is_convertible_v<sys_time<_Duration2>, sys_time<_Duration>>
zoned_time(
_TimeZonePtr _Tz, const zoned_time<_Duration2, _TimeZonePtr2>& _Zt, choose) noexcept /* strengthened */
: zoned_time{_Tz, _Zt} {}
: _Zone{_STD move(_Tz)}, _Tp{_Zt.get_sys_time()} {}

template <class _Duration2, class _TimeZonePtr2, class _Traits2 = _Traits,
enable_if_t<is_constructible_v<zoned_time, decltype(_Traits2::locate_zone(string_view{})),
const zoned_time<_Duration2, _TimeZonePtr2>&>,
int> = 0>
template <class _Duration2, class _TimeZonePtr2>
zoned_time(string_view _Name, const zoned_time<_Duration2, _TimeZonePtr2>& _Zt)
: zoned_time{_Traits::locate_zone(_Name), _Zt} {}

template <class _Duration2, class _TimeZonePtr2, class _Traits2 = _Traits,
enable_if_t<is_constructible_v<zoned_time, decltype(_Traits2::locate_zone(string_view{})),
const zoned_time<_Duration2, _TimeZonePtr2>&, choose>,
int> = 0>
zoned_time(string_view _Name, const zoned_time<_Duration2, _TimeZonePtr2>& _Zt, choose _Choose)
: zoned_time{_Traits::locate_zone(_Name), _Zt, _Choose} {}
requires requires {
{ _Traits::locate_zone(_Name) } -> convertible_to<_TimeZonePtr>;
} && is_convertible_v<sys_time<_Duration2>, sys_time<_Duration>>
: _Zone{_Traits::locate_zone(_Name)}, _Tp{_Zt.get_sys_time()} {}

template <class _Duration2, class _TimeZonePtr2>
zoned_time(string_view _Name, const zoned_time<_Duration2, _TimeZonePtr2>& _Zt, choose)
requires requires {
{ _Traits::locate_zone(_Name) } -> convertible_to<_TimeZonePtr>;
} && is_convertible_v<sys_time<_Duration2>, sys_time<_Duration>>
: _Zone{_Traits::locate_zone(_Name)}, _Tp{_Zt.get_sys_time()} {}

zoned_time& operator=(const sys_time<_Duration>& _Sys) noexcept /* strengthened */ {
_Tp = _Sys;
Expand Down