Support offset time zones in Intl.DTF polyfill

In Node 23, offset time zone IDs are now supported by
`Intl.DateTimeFormat`.

This commit changes the polyfill to handle these IDs.

Author: justingrant

lib/intl.ts

@@ -162,13 +162,13 @@ function createDateTimeFormat(
     SetSlot(dtf, TZ_ORIGINAL, ro.timeZone);
   } else {
     const id = ES.ToString(timeZoneOption);
-    if (ES.IsOffsetTimeZoneIdentifier(id)) {
-      // Note: https://github.com/tc39/ecma402/issues/683 will remove this
-      throw new RangeError('Intl.DateTimeFormat does not currently support offset time zones');
+    if (id.startsWith('−')) {
+      // The initial (Node 23) implementation of offset time zones allowed use
+      // of the Unicode minus sign, which was disallowed by a later spec change.
+      throw new RangeError('Unicode minus (U+2212) is not supported in time zone offsets');
     }
-    const record = ES.GetAvailableNamedTimeZoneIdentifier(id);
-    if (!record) throw new RangeError(`Intl.DateTimeFormat formats built-in time zones, not ${id}`);
-    SetSlot(dtf, TZ_ORIGINAL, record.identifier);
+    // store a normalized identifier
+    SetSlot(dtf, TZ_ORIGINAL, ES.ToTemporalTimeZoneIdentifier(id));
   }
   return undefined; // TODO: I couldn't satisfy TS without adding this. Is there another way?
 }

test/expected-failures.txt

@@ -6,13 +6,6 @@
 # canonicalizing the timezone name.
 staging/Intl402/Temporal/old/date-time-format.js
 
-# These are caught by the default test glob, but are unrelated to Temporal.
-# They rely on Intl.DateTimeFormat supporting offset time zones.
-intl402/DateTimeFormat/prototype/format/offset-timezone-gmt-same.js
-intl402/DateTimeFormat/prototype/formatToParts/offset-timezone-correct.js
-intl402/DateTimeFormat/prototype/resolvedOptions/offset-timezone-basic.js
-intl402/DateTimeFormat/prototype/resolvedOptions/offset-timezone-change.js
-
 # https://github.com/tc39/test262/pull/4336
 intl402/DateTimeFormat/canonicalize-utc-timezone.js