[llvm-branch-commits] [libcxx] [libc++][TZDB] Finishes zoned_time constructors. (PR #95010)

[Louis Dionne via llvm-branch-commits]

================
@@ -76,12 +81,71 @@ class zoned_time {
 
   _LIBCPP_HIDE_FROM_ABI explicit zoned_time(string_view __name)
     requires(requires { __traits::locate_zone(string_view{}); } &&
-             // constructible_from<zoned_time, decltype(__traits::locate_zone(string_view{}))>
-             // would create a dependency on itself. Instead depend on the fact
-             // a constructor taking a _TimeZonePtr exists.
              constructible_from<_TimeZonePtr, decltype(__traits::locate_zone(string_view{}))>)
       : __zone_{__traits::locate_zone(__name)}, __tp_{} {}
 
+  template <class _Duration2>
+  _LIBCPP_HIDE_FROM_ABI zoned_time(const zoned_time<_Duration2, _TimeZonePtr>& __zt)
+    requires is_convertible_v<sys_time<_Duration2>, sys_time<_Duration>>
+      : __zone_{__zt.get_time_zone()}, __tp_{__zt.get_sys_time()} {}
+
+  _LIBCPP_HIDE_FROM_ABI zoned_time(_TimeZonePtr __zone, const sys_time<_Duration>& __tp)
+      : __zone_{std::move(__zone)}, __tp_{__tp} {}
+
+  _LIBCPP_HIDE_FROM_ABI zoned_time(string_view __name, const sys_time<_Duration>& __tp)
+    requires requires { _TimeZonePtr{__traits::locate_zone(string_view{})}; }
+      : zoned_time{__traits::locate_zone(__name), __tp} {}
+
+  _LIBCPP_HIDE_FROM_ABI zoned_time(_TimeZonePtr __zone, const local_time<_Duration>& __tp)
+    requires(is_convertible_v<decltype(std::declval<_TimeZonePtr&>() -> to_sys(local_time<_Duration>{})),
+                              sys_time<duration>>)
+      : __zone_{std::move(__zone)}, __tp_{__zone_->to_sys(__tp)} {}
+
+  _LIBCPP_HIDE_FROM_ABI zoned_time(string_view __name, const local_time<_Duration>& __tp)
+    requires(requires {
+      _TimeZonePtr{__traits::locate_zone(string_view{})};
+    } && is_convertible_v<decltype(std::declval<_TimeZonePtr&>() -> to_sys(local_time<_Duration>{})),
----------------
ldionne wrote:

```suggestion
    requires is_constructible<zoned_time, decltype(__traits::locate_zone(__name))> && is_convertible_v<decltype(std::declval<_TimeZonePtr&>() -> to_sys(local_time<_Duration>{})),
```

The constraint in http://eel.is/c++draft/time.zone#zonedtime.ctor-18.sentence-1 is:
> Constraints: zoned_time is constructible from the return type of `traits​::​locate_zone(name)` and `tp`.

https://github.com/llvm/llvm-project/pull/95010