Eliminate duplication between Duration Records and Temporal.Duration instances

polyfill/lib/calendar.mjs

@@ -167,7 +167,14 @@ impl['iso8601'] = {
     return arrayFromSet(result);
   },
   dateAdd({ year, month, day }, { years = 0, months = 0, weeks = 0, days = 0 }, overflow) {
-    return ES.AddISODate(year, month, day, years, months, weeks, days, overflow);
+    year += years;
+    month += months;
+    ({ year, month } = ES.BalanceISOYearMonth(year, month));
+    ({ year, month, day } = ES.RegulateISODate(year, month, day, overflow));
+    day += days + 7 * weeks;
+    ({ year, month, day } = ES.BalanceISODate(year, month, day));
+    ES.RejectDateRange(year, month, day);
+    return { year, month, day };
   },
   dateUntil(one, two, largestUnit) {
     return ES.DifferenceISODate(one.year, one.month, one.day, two.year, two.month, two.day, largestUnit);
@@ -722,7 +729,7 @@ const nonIsoHelperBase = {
     return this.isoToCalendarDate(isoDate, cache);
   },
   addDaysIso(isoDate, days) {
-    const added = ES.AddISODate(isoDate.year, isoDate.month, isoDate.day, 0, 0, 0, days, 'constrain');
+    const added = ES.BalanceISODate(isoDate.year, isoDate.month, isoDate.day + days);
     return added;
   },
   addDaysCalendar(calendarDate, days, cache) {
@@ -1174,7 +1181,7 @@ const helperIndian = ObjectAssign({}, nonIsoHelperBase, {
     const isoYear = calendarDate.year + 78 + (monthInfo.nextYear ? 1 : 0);
     const isoMonth = monthInfo.month;
     const isoDay = monthInfo.day;
-    const isoDate = ES.AddISODate(isoYear, isoMonth, isoDay, 0, 0, 0, calendarDate.day - 1, 'constrain');
+    const isoDate = ES.BalanceISODate(isoYear, isoMonth, isoDay + calendarDate.day - 1);
     return isoDate;
   },
   // https://bugs.chromium.org/p/v8/issues/detail?id=10529 causes Intl's Indian