Revert "[libc++][TZDB] Implements zoned_traits. (llvm#91059)"

This reverts commit 151bd7c.

Author: fmayer

libcxx/include/CMakeLists.txt

@@ -277,7 +277,6 @@ set(files
   __chrono/year_month.h
   __chrono/year_month_day.h
   __chrono/year_month_weekday.h
-  __chrono/zoned_time.h
   __compare/common_comparison_category.h
   __compare/compare_partial_order_fallback.h
   __compare/compare_strong_order_fallback.h

libcxx/include/__chrono/zoned_time.h

@@ -786,9 +786,6 @@ class time_zone {
 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
 
-// [time.zone.zonedtraits], class template zoned_traits
-template<class T> struct zoned_traits;                                           // C++20
-
 // [time.zone.leap], leap second support
 class leap_second {                                                              // C++20
 public:
@@ -962,7 +959,6 @@ constexpr chrono::year                                  operator ""y(unsigned lo
 #    include <__chrono/time_zone_link.h>
 #    include <__chrono/tzdb.h>
 #    include <__chrono/tzdb_list.h>
-#    include <__chrono/zoned_time.h>
 #  endif
 
 #endif

libcxx/include/chrono

@@ -1159,7 +1159,6 @@ module std_private_chrono_year                   [system] { header "__chrono/yea
 module std_private_chrono_year_month             [system] { header "__chrono/year_month.h" }
 module std_private_chrono_year_month_day         [system] { header "__chrono/year_month_day.h" }
 module std_private_chrono_year_month_weekday     [system] { header "__chrono/year_month_weekday.h" }
-module std_private_chrono_zoned_time             [system] { header "__chrono/zoned_time.h" }
 
 module std_private_compare_common_comparison_category     [system] { header "__compare/common_comparison_category.h" }
 module std_private_compare_compare_partial_order_fallback [system] { header "__compare/compare_partial_order_fallback.h" }

libcxx/include/module.modulemap

@@ -227,10 +227,11 @@ export namespace std {
     using std::chrono::choose;
     using std::chrono::time_zone;
 
+#    if 0
+
     // [time.zone.zonedtraits], class template zoned_traits
     using std::chrono::zoned_traits;
 
-#    if 0
     // [time.zone.zonedtime], class template zoned_time
     using std::chrono::zoned_time;
 

libcxx/modules/std/chrono.inc

@@ -72,10 +72,4 @@ void test() {
     leap.date();  // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
     leap.value(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
   }
-
-  {
-    using t = std::chrono::zoned_traits<const std::chrono::time_zone*>;
-    t::default_zone();  // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
-    t::locate_zone(""); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
-  }
 }