Revert "[libc++][TZDB] Implements time_zone::to_sys. (llvm#90901)"

This reverts commit 87cedbe.

Author: fmayer

libcxx/include/__chrono/time_zone.h

@@ -42,8 +42,6 @@ _LIBCPP_BEGIN_NAMESPACE_STD
 
 namespace chrono {
 
-enum class choose { earliest, latest };
-
 class _LIBCPP_AVAILABILITY_TZDB time_zone {
   _LIBCPP_HIDE_FROM_ABI time_zone() = default;
 
@@ -99,36 +97,6 @@ class _LIBCPP_AVAILABILITY_TZDB time_zone {
     return {};
   }
 
-  template <class _Duration>
-  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI sys_time<common_type_t<_Duration, seconds>>
-  to_sys(const local_time<_Duration>& __time, choose __z) const {
-    local_info __info = get_info(__time);
-    switch (__info.result) {
-    case local_info::unique:
-    case local_info::nonexistent: // first and second are the same
-      return sys_time<common_type_t<_Duration, seconds>>{__time.time_since_epoch() - __info.first.offset};
-
-    case local_info::ambiguous:
-      switch (__z) {
-      case choose::earliest:
-        return sys_time<common_type_t<_Duration, seconds>>{__time.time_since_epoch() - __info.first.offset};
-
-      case choose::latest:
-        return sys_time<common_type_t<_Duration, seconds>>{__time.time_since_epoch() - __info.second.offset};
-
-        // Note a value out of bounds is not specified.
-      }
-    }
-
-    // TODO TZDB The standard does not specify anything in these cases.
-    _LIBCPP_ASSERT_ARGUMENT_WITHIN_DOMAIN(
-        __info.result != -1, "cannot convert the local time; it would be before the minimum system clock value");
-    _LIBCPP_ASSERT_ARGUMENT_WITHIN_DOMAIN(
-        __info.result != -2, "cannot convert the local time; it would be after the maximum system clock value");
-
-    return {};
-  }
-
   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI const __impl& __implementation() const noexcept { return *__impl_; }
 
 private:

libcxx/include/chrono

@@ -774,10 +774,6 @@ class time_zone {
   template<class Duration>
   sys_time<common_type_t<Duration, seconds>>
     to_sys(const local_time<Duration>& tp) const;
-
-  template<class Duration>
-  sys_time<common_type_t<Duration, seconds>>
-    to_sys(const local_time<Duration>& tp, choose z) const;
 };
 bool operator==(const time_zone& x, const time_zone& y) noexcept;                // C++20
 strong_ordering operator<=>(const time_zone& x, const time_zone& y) noexcept;    // C++20

libcxx/modules/std/chrono.inc

@@ -223,8 +223,11 @@ export namespace std {
 #  if !defined(_LIBCPP_HAS_NO_TIME_ZONE_DATABASE) && !defined(_LIBCPP_HAS_NO_FILESYSTEM) &&                            \
       !defined(_LIBCPP_HAS_NO_LOCALIZATION)
 
+#    if 0
     // [time.zone.timezone], class time_zone
     using std::chrono::choose;
+#    endif // if 0
+
     using std::chrono::time_zone;
 
 #    if 0

libcxx/test/libcxx/diagnostics/chrono.nodiscard.verify.cpp

@@ -49,12 +49,9 @@ void test() {
   {
     std::chrono::sys_seconds s{};
     std::chrono::local_seconds l{};
-    std::chrono::choose z = std::chrono::choose::earliest;
     tz.name();           // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
     tz.get_info(s);      // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
     tz.get_info(l);      // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
-    tz.to_sys(l);        // not nodiscard
-    tz.to_sys(l, z);     // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
     operator==(tz, tz);  // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
     operator<=>(tz, tz); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
   }