LibJS: Mark CreateTemporalDate in AddDateTime as infallible

This is an editorial change in the Temporal spec.

See: https://github.com/tc39/proposal-temporal/commit/cd356a6

Userland/Libraries/LibJS/Runtime/Temporal/PlainDateTime.cpp

@@ -307,19 +307,22 @@ i8 compare_iso_date_time(i32 year1, u8 month1, u8 day1, u8 hour1, u8 minute1, u8
 // 5.5.9 AddDateTime ( year, month, day, hour, minute, second, millisecond, microsecond, nanosecond, calendar, years, months, weeks, days, hours, minutes, seconds, milliseconds, microseconds, nanoseconds, options ), https://tc39.es/proposal-temporal/#sec-temporal-adddatetime
 ThrowCompletionOr<TemporalPlainDateTime> add_date_time(GlobalObject& global_object, i32 year, u8 month, u8 day, u8 hour, u8 minute, u8 second, u16 millisecond, u16 microsecond, u16 nanosecond, Object& calendar, double years, double months, double weeks, double days, double hours, double minutes, double seconds, double milliseconds, double microseconds, double nanoseconds, Object* options)
 {
-    // 1. Let timeResult be ! AddTime(hour, minute, second, millisecond, microsecond, nanosecond, hours, minutes, seconds, milliseconds, microseconds, nanoseconds).
+    // 1. Assert: ISODateTimeWithinLimits(year, month, day, hour, minute, second, millisecond, microsecond, nanosecond) is true.
+    VERIFY(iso_date_time_within_limits(global_object, year, month, day, hour, minute, second, millisecond, microsecond, nanosecond));
+
+    // 2. Let timeResult be ! AddTime(hour, minute, second, millisecond, microsecond, nanosecond, hours, minutes, seconds, milliseconds, microseconds, nanoseconds).
     auto time_result = add_time(hour, minute, second, millisecond, microsecond, nanosecond, hours, minutes, seconds, milliseconds, microseconds, nanoseconds);
 
-    // 2. Let datePart be ? CreateTemporalDate(year, month, day, calendar).
-    auto* date_part = TRY(create_temporal_date(global_object, year, month, day, calendar));
+    // 3. Let datePart be ! CreateTemporalDate(year, month, day, calendar).
+    auto* date_part = MUST(create_temporal_date(global_object, year, month, day, calendar));
 
-    // 3. Let dateDuration be ? CreateTemporalDuration(years, months, weeks, days + timeResult.[[Days]], 0, 0, 0, 0, 0, 0).
+    // 4. Let dateDuration be ? CreateTemporalDuration(years, months, weeks, days + timeResult.[[Days]], 0, 0, 0, 0, 0, 0).
     auto* date_duration = TRY(create_temporal_duration(global_object, years, months, weeks, days + time_result.days, 0, 0, 0, 0, 0, 0));
 
-    // 4. Let addedDate be ? CalendarDateAdd(calendar, datePart, dateDuration, options).
+    // 5. Let addedDate be ? CalendarDateAdd(calendar, datePart, dateDuration, options).
     auto* added_date = TRY(calendar_date_add(global_object, calendar, date_part, *date_duration, options));
 
-    // 5. Return the Record { [[Year]]: addedDate.[[ISOYear]], [[Month]]: addedDate.[[ISOMonth]], [[Day]]: addedDate.[[ISODay]], [[Hour]]: timeResult.[[Hour]], [[Minute]]: timeResult.[[Minute]], [[Second]]: timeResult.[[Second]], [[Millisecond]]: timeResult.[[Millisecond]], [[Microsecond]]: timeResult.[[Microsecond]], [[Nanosecond]]: timeResult.[[Nanosecond]] }.
+    // 6. Return the Record { [[Year]]: addedDate.[[ISOYear]], [[Month]]: addedDate.[[ISOMonth]], [[Day]]: addedDate.[[ISODay]], [[Hour]]: timeResult.[[Hour]], [[Minute]]: timeResult.[[Minute]], [[Second]]: timeResult.[[Second]], [[Millisecond]]: timeResult.[[Millisecond]], [[Microsecond]]: timeResult.[[Microsecond]], [[Nanosecond]]: timeResult.[[Nanosecond]] }.
     return TemporalPlainDateTime { .year = added_date->iso_year(), .month = added_date->iso_month(), .day = added_date->iso_day(), .hour = time_result.hour, .minute = time_result.minute, .second = time_result.second, .millisecond = time_result.millisecond, .microsecond = time_result.microsecond, .nanosecond = time_result.nanosecond };
 }