[libc++][chrono] P2592R3: Hashing for chrono

libcxx/docs/ReleaseNotes/22.rst

@@ -38,6 +38,7 @@ What's New in Libc++ 22.0.0?
 Implemented Papers
 ------------------
 
+- P2592R3: Hashing support for ``std::chrono`` value classes (`Github <https://llvm.org/PR105358>`__)
 - P2321R2: ``zip`` (`Github <https://llvm.org/PR105169>`__) (The paper is partially implemented. ``zip_transform_view``
   is implemented in this release)
 - P3044R2: sub-``string_view`` from ``string`` (`Github <https://llvm.org/PR148140>`__)

libcxx/docs/Status/Cxx2cPapers.csv

@@ -1,6 +1,6 @@
 "Paper #","Paper Name","Meeting","Status","First released version","GitHub issue","Notes"
 "`P2497R0 <https://wg21.link/P2497R0>`__","Testing for success or failure of ``<charconv>`` functions","2023-06 (Varna)","|Complete|","18","`#105357 <https://github.com/llvm/llvm-project/issues/105357>`__",""
-"`P2592R3 <https://wg21.link/P2592R3>`__","Hashing support for ``std::chrono`` value classes","2023-06 (Varna)","","","`#105358 <https://github.com/llvm/llvm-project/issues/105358>`__",""
+"`P2592R3 <https://wg21.link/P2592R3>`__","Hashing support for ``std::chrono`` value classes","2023-06 (Varna)","|Complete|","22","`#105358 <https://github.com/llvm/llvm-project/issues/105358>`__",""
 "`P2587R3 <https://wg21.link/P2587R3>`__","``to_string`` or not ``to_string``","2023-06 (Varna)","","","`#105359 <https://github.com/llvm/llvm-project/issues/105359>`__",""
 "`P2562R1 <https://wg21.link/P2562R1>`__","``constexpr`` Stable Sorting","2023-06 (Varna)","|Complete|","21","`#105360 <https://github.com/llvm/llvm-project/issues/105360>`__",""
 "`P2545R4 <https://wg21.link/P2545R4>`__","Read-Copy Update (RCU)","2023-06 (Varna)","","","`#105361 <https://github.com/llvm/llvm-project/issues/105361>`__",""

libcxx/include/__chrono/day.h

@@ -13,6 +13,8 @@
 #include <__chrono/duration.h>
 #include <__compare/ordering.h>
 #include <__config>
+#include <__cstddef/size_t.h>
+#include <__functional/hash.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
@@ -92,6 +94,15 @@ _LIBCPP_HIDE_FROM_ABI inline constexpr day& day::operator-=(const days& __dd) no
 
 } // namespace chrono
 
+#  if _LIBCPP_STD_VER >= 26
+
+template <>
+struct hash<chrono::day> {
+  _LIBCPP_HIDE_FROM_ABI static size_t operator()(const chrono::day& __d) noexcept { return static_cast<unsigned>(__d); }
+};
+
+#  endif // _LIBCPP_STD_VER >= 26
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP_STD_VER >= 20

libcxx/include/__chrono/duration.h

@@ -13,6 +13,8 @@
 #include <__compare/ordering.h>
 #include <__compare/three_way_comparable.h>
 #include <__config>
+#include <__cstddef/size_t.h>
+#include <__functional/hash.h>
 #include <__type_traits/common_type.h>
 #include <__type_traits/enable_if.h>
 #include <__type_traits/is_convertible.h>
@@ -538,6 +540,18 @@ using namespace literals::chrono_literals;
 
 #endif // _LIBCPP_STD_VER >= 14
 
+#if _LIBCPP_STD_VER >= 26
+
+template <class _Rep, class _Period>
+  requires __has_enabled_hash<_Rep>::value
+struct hash<chrono::duration<_Rep, _Period>> {
+  _LIBCPP_HIDE_FROM_ABI static size_t operator()(const chrono::duration<_Rep, _Period>& __d) {
+    return hash<_Rep>{}(__d.count());
+  }
+};
+
+#endif // _LIBCPP_STD_VER >= 26
+
 _LIBCPP_END_NAMESPACE_STD
 
 _LIBCPP_POP_MACROS

libcxx/include/__chrono/leap_second.h

@@ -22,6 +22,8 @@
 #  include <__compare/ordering.h>
 #  include <__compare/three_way_comparable.h>
 #  include <__config>
+#  include <__cstddef/size_t.h>
+#  include <__functional/hash.h>
 #  include <__utility/private_constructor_tag.h>
 
 #  if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
@@ -122,6 +124,17 @@ class leap_second {
 
 } // namespace chrono
 
+#    if _LIBCPP_STD_VER >= 26
+
+template <>
+struct hash<chrono::leap_second> {
+  _LIBCPP_HIDE_FROM_ABI static size_t operator()(const chrono::leap_second& __lp) noexcept {
+    return std::__hash_combine(hash<chrono::sys_seconds>{}(__lp.date()), hash<chrono::seconds>{}(__lp.value()));
+  }
+};
+
+#    endif // _LIBCPP_STD_VER >= 26
+
 #  endif // _LIBCPP_STD_VER >= 20
 
 _LIBCPP_END_NAMESPACE_STD

libcxx/include/__chrono/month.h

@@ -13,6 +13,8 @@
 #include <__chrono/duration.h>
 #include <__compare/ordering.h>
 #include <__config>
+#include <__cstddef/size_t.h>
+#include <__functional/hash.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
@@ -108,6 +110,17 @@ inline constexpr month December{12};
 
 } // namespace chrono
 
+#  if _LIBCPP_STD_VER >= 26
+
+template <>
+struct hash<chrono::month> {
+  _LIBCPP_HIDE_FROM_ABI static size_t operator()(const chrono::month& __m) noexcept {
+    return static_cast<unsigned>(__m);
+  }
+};
+
+#  endif // _LIBCPP_STD_VER >= 26
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP_STD_VER >= 20

libcxx/include/__chrono/month_weekday.h

@@ -13,6 +13,8 @@
 #include <__chrono/month.h>
 #include <__chrono/weekday.h>
 #include <__config>
+#include <__cstddef/size_t.h>
+#include <__functional/hash.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
@@ -98,6 +100,26 @@ _LIBCPP_HIDE_FROM_ABI inline constexpr month_weekday_last operator/(const weekda
 }
 } // namespace chrono
 
+#  if _LIBCPP_STD_VER >= 26
+
+template <>
+struct hash<chrono::month_weekday> {
+  _LIBCPP_HIDE_FROM_ABI static size_t operator()(const chrono::month_weekday& __mw) noexcept {
+    return std::__hash_combine(
+        hash<chrono::month>{}(__mw.month()), hash<chrono::weekday_indexed>{}(__mw.weekday_indexed()));
+  }
+};
+
+template <>
+struct hash<chrono::month_weekday_last> {
+  _LIBCPP_HIDE_FROM_ABI static size_t operator()(const chrono::month_weekday_last& __mwl) noexcept {
+    return std::__hash_combine(
+        hash<chrono::month>{}(__mwl.month()), hash<chrono::weekday_last>{}(__mwl.weekday_last()));
+  }
+};
+
+#  endif // _LIBCPP_STD_VER >= 26
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP_STD_VER >= 20

libcxx/include/__chrono/monthday.h

@@ -15,6 +15,8 @@
 #include <__chrono/month.h>
 #include <__compare/ordering.h>
 #include <__config>
+#include <__cstddef/size_t.h>
+#include <__functional/hash.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
@@ -126,6 +128,24 @@ _LIBCPP_HIDE_FROM_ABI inline constexpr month_day_last operator/(last_spec, int _
 
 } // namespace chrono
 
+#  if _LIBCPP_STD_VER >= 26
+
+template <>
+struct hash<chrono::month_day> {
+  _LIBCPP_HIDE_FROM_ABI static size_t operator()(const chrono::month_day& __md) noexcept {
+    return std::__hash_combine(hash<chrono::month>{}(__md.month()), hash<chrono::day>{}(__md.day()));
+  }
+};
+
+template <>
+struct hash<chrono::month_day_last> {
+  _LIBCPP_HIDE_FROM_ABI static size_t operator()(const chrono::month_day_last& __mdl) noexcept {
+    return hash<chrono::month>{}(__mdl.month());
+  }
+};
+
+#  endif // _LIBCPP_STD_VER >= 26
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP_STD_VER >= 20

libcxx/include/__chrono/time_point.h

@@ -14,6 +14,8 @@
 #include <__compare/ordering.h>
 #include <__compare/three_way_comparable.h>
 #include <__config>
+#include <__cstddef/size_t.h>
+#include <__functional/hash.h>
 #include <__type_traits/common_type.h>
 #include <__type_traits/enable_if.h>
 #include <__type_traits/is_convertible.h>
@@ -224,6 +226,18 @@ operator-(const time_point<_Clock, _Duration1>& __lhs, const time_point<_Clock,
 
 } // namespace chrono
 
+#if _LIBCPP_STD_VER >= 26
+
+template <class _Clock, class _Duration>
+  requires __has_enabled_hash<_Duration>::value
+struct hash<chrono::time_point<_Clock, _Duration>> {
+  _LIBCPP_HIDE_FROM_ABI static size_t operator()(const chrono::time_point<_Clock, _Duration>& __tp) {
+    return hash<_Duration>{}(__tp.time_since_epoch());
+  }
+};
+
+#endif // _LIBCPP_STD_VER >= 26
+
 _LIBCPP_END_NAMESPACE_STD
 
 _LIBCPP_POP_MACROS

libcxx/include/__chrono/weekday.h

@@ -15,6 +15,8 @@
 #include <__chrono/system_clock.h>
 #include <__chrono/time_point.h>
 #include <__config>
+#include <__cstddef/size_t.h>
+#include <__functional/hash.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
@@ -160,6 +162,29 @@ inline constexpr weekday Saturday{6};
 
 } // namespace chrono
 
+#  if _LIBCPP_STD_VER >= 26
+
+template <>
+struct hash<chrono::weekday> {
+  _LIBCPP_HIDE_FROM_ABI static size_t operator()(const chrono::weekday& __w) noexcept { return __w.c_encoding(); }
+};
+
+template <>
+struct hash<chrono::weekday_indexed> {
+  _LIBCPP_HIDE_FROM_ABI static size_t operator()(const chrono::weekday_indexed& __wi) noexcept {
+    return std::__hash_combine(hash<chrono::weekday>{}(__wi.weekday()), __wi.index());
+  }
+};
+
+template <>
+struct hash<chrono::weekday_last> {
+  _LIBCPP_HIDE_FROM_ABI static size_t operator()(const chrono::weekday_last& __wl) noexcept {
+    return hash<chrono::weekday>{}(__wl.weekday());
+  }
+};
+
+#  endif // _LIBCPP_STD_VER >= 26
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP_STD_VER >= 20

libcxx/include/__chrono/year.h

@@ -13,6 +13,8 @@
 #include <__chrono/duration.h>
 #include <__compare/ordering.h>
 #include <__config>
+#include <__cstddef/size_t.h>
+#include <__functional/hash.h>
 #include <limits>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
@@ -109,6 +111,15 @@ _LIBCPP_HIDE_FROM_ABI constexpr bool year::ok() const noexcept {
 
 } // namespace chrono
 
+#  if _LIBCPP_STD_VER >= 26
+
+template <>
+struct hash<chrono::year> {
+  _LIBCPP_HIDE_FROM_ABI static size_t operator()(const chrono::year& __y) noexcept { return static_cast<int>(__y); }
+};
+
+#  endif // _LIBCPP_STD_VER >= 26
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP_STD_VER >= 20

libcxx/include/__chrono/year_month.h

@@ -15,6 +15,8 @@
 #include <__chrono/year.h>
 #include <__compare/ordering.h>
 #include <__config>
+#include <__cstddef/size_t.h>
+#include <__functional/hash.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
@@ -116,6 +118,17 @@ _LIBCPP_HIDE_FROM_ABI inline constexpr year_month& year_month::operator-=(const
 
 } // namespace chrono
 
+#  if _LIBCPP_STD_VER >= 26
+
+template <>
+struct hash<chrono::year_month> {
+  _LIBCPP_HIDE_FROM_ABI static size_t operator()(const chrono::year_month& __ym) noexcept {
+    return std::__hash_combine(hash<chrono::year>{}(__ym.year()), hash<chrono::month>{}(__ym.month()));
+  }
+};
+
+#  endif // _LIBCPP_STD_VER >= 26
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP_STD_VER >= 20

libcxx/include/__chrono/year_month_day.h

@@ -21,6 +21,8 @@
 #include <__chrono/year_month.h>
 #include <__compare/ordering.h>
 #include <__config>
+#include <__cstddef/size_t.h>
+#include <__functional/hash.h>
 #include <limits>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
@@ -330,6 +332,27 @@ _LIBCPP_HIDE_FROM_ABI inline constexpr bool year_month_day::ok() const noexcept
 
 } // namespace chrono
 
+#  if _LIBCPP_STD_VER >= 26
+
+template <>
+struct hash<chrono::year_month_day> {
+  _LIBCPP_HIDE_FROM_ABI static size_t operator()(const chrono::year_month_day& __ymd) noexcept {
+    return std::__hash_combine(
+        hash<chrono::year>{}(__ymd.year()),
+        std::__hash_combine(hash<chrono::month>{}(__ymd.month()), hash<chrono::day>{}(__ymd.day())));
+  }
+};
+
+template <>
+struct hash<chrono::year_month_day_last> {
+  _LIBCPP_HIDE_FROM_ABI static size_t operator()(const chrono::year_month_day_last& __ymdl) noexcept {
+    return std::__hash_combine(
+        hash<chrono::year>{}(__ymdl.year()), hash<chrono::month_day_last>{}(__ymdl.month_day_last()));
+  }
+};
+
+#  endif // _LIBCPP_STD_VER >= 26
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP_STD_VER >= 20

libcxx/include/__chrono/year_month_weekday.h

@@ -22,6 +22,8 @@
 #include <__chrono/year_month.h>
 #include <__chrono/year_month_day.h>
 #include <__config>
+#include <__cstddef/size_t.h>
+#include <__functional/hash.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
@@ -280,6 +282,30 @@ year_month_weekday_last::operator-=(const years& __dy) noexcept {
 
 } // namespace chrono
 
+#  if _LIBCPP_STD_VER >= 26
+
+template <>
+struct hash<chrono::year_month_weekday> {
+  _LIBCPP_HIDE_FROM_ABI static size_t operator()(const chrono::year_month_weekday& __ymw) noexcept {
+    return std::__hash_combine(
+        hash<chrono::year>{}(__ymw.year()),
+        std::__hash_combine(
+            hash<chrono::month>{}(__ymw.month()), hash<chrono::weekday_indexed>{}(__ymw.weekday_indexed())));
+  }
+};
+
+template <>
+struct hash<chrono::year_month_weekday_last> {
+  _LIBCPP_HIDE_FROM_ABI static size_t operator()(const chrono::year_month_weekday_last& __ymwl) noexcept {
+    return std::__hash_combine(
+        hash<chrono::year>{}(__ymwl.year()),
+        std::__hash_combine(
+            hash<chrono::month>{}(__ymwl.month()), hash<chrono::weekday_last>{}(__ymwl.weekday_last())));
+  }
+};
+
+#  endif // _LIBCPP_STD_VER >= 26
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP_STD_VER >= 20