diff --git a/polyfill/index.d.ts b/polyfill/index.d.ts
index d8a202c788..39e2784ee7 100644
--- a/polyfill/index.d.ts
+++ b/polyfill/index.d.ts
@@ -603,8 +603,9 @@ export namespace Temporal {
     readonly [Symbol.toStringTag]: 'Temporal.Instant';
   }
 
-  type EitherYearOrEraAndEraYear = { era: string; eraYear: number } | { year: number };
-  type EitherMonthCodeOrMonthAndYear = (EitherYearOrEraAndEraYear & { month: number }) | { monthCode: string };
+  type YearOrEraAndEraYear = { era: string; eraYear: number } | { year: number };
+  type MonthCodeOrMonthAndYear = (YearOrEraAndEraYear & { month: number }) | { monthCode: string };
+  type MonthOrMonthCode = { month: number } | { monthCode: string };
 
   export interface CalendarProtocol {
     id?: string;
@@ -648,15 +649,15 @@ export namespace Temporal {
       date: Temporal.PlainDate | Temporal.PlainDateTime | Temporal.PlainYearMonth | PlainDateLike | string
     ): boolean;
     dateFromFields(
-      fields: EitherMonthCodeOrMonthAndYear & { day: number },
+      fields: YearOrEraAndEraYear & MonthOrMonthCode & { day: number },
       options?: AssignmentOptions
     ): Temporal.PlainDate;
     yearMonthFromFields(
-      fields: EitherYearOrEraAndEraYear & ({ month: number } | { monthCode: string }),
+      fields: YearOrEraAndEraYear & MonthOrMonthCode,
       options?: AssignmentOptions
     ): Temporal.PlainYearMonth;
     monthDayFromFields(
-      fields: EitherMonthCodeOrMonthAndYear & { day: number },
+      fields: MonthCodeOrMonthAndYear & { day: number },
       options?: AssignmentOptions
     ): Temporal.PlainMonthDay;
     dateAdd(
@@ -726,15 +727,15 @@ export namespace Temporal {
       date: Temporal.PlainDate | Temporal.PlainDateTime | Temporal.PlainYearMonth | PlainDateLike | string
     ): boolean;
     dateFromFields(
-      fields: EitherMonthCodeOrMonthAndYear & { day: number },
+      fields: YearOrEraAndEraYear & MonthOrMonthCode & { day: number },
       options?: AssignmentOptions
     ): Temporal.PlainDate;
     yearMonthFromFields(
-      fields: EitherYearOrEraAndEraYear & ({ month: number } | { monthCode: string }),
+      fields: YearOrEraAndEraYear & MonthOrMonthCode,
       options?: AssignmentOptions
     ): Temporal.PlainYearMonth;
     monthDayFromFields(
-      fields: EitherMonthCodeOrMonthAndYear & { day: number },
+      fields: MonthCodeOrMonthAndYear & { day: number },
       options?: AssignmentOptions
     ): Temporal.PlainMonthDay;
     dateAdd(
diff --git a/polyfill/lib/calendar.mjs b/polyfill/lib/calendar.mjs
index 92942d8cad..b2b68efee2 100644
--- a/polyfill/lib/calendar.mjs
+++ b/polyfill/lib/calendar.mjs
@@ -26,6 +26,7 @@ import {
 const ArrayIncludes = Array.prototype.includes;
 const ArrayPrototypePush = Array.prototype.push;
 const IntlDateTimeFormat = globalThis.Intl.DateTimeFormat;
+const ArraySort = Array.prototype.sort;
 const MathAbs = Math.abs;
 const MathFloor = Math.floor;
 const ObjectAssign = Object.assign;
@@ -418,7 +419,7 @@ class OneObjectCache {
     this.hits = 0;
     this.misses = 0;
     if (cacheToClone !== undefined) {
-      let i = cacheToClone.length;
+      let i = 0;
       for (const entry of cacheToClone.map.entries()) {
         if (++i > OneObjectCache.MAX_CACHE_ENTRIES) break;
         this.map.set(...entry);
@@ -509,7 +510,7 @@ const nonIsoHelperBase = {
     return this.formatter;
   },
   isoToCalendarDate(isoDate, cache) {
-    let { year: isoYear, month: isoMonth, day: isoDay } = isoDate;
+    const { year: isoYear, month: isoMonth, day: isoDay } = isoDate;
     const key = JSON.stringify({ func: 'isoToCalendarDate', isoYear, isoMonth, isoDay, id: this.id });
     const cached = cache.get(key);
     if (cached) return cached;
@@ -575,8 +576,7 @@ const nonIsoHelperBase = {
       result.era = era;
       result.eraYear = eraYear;
     }
-    if (this.checkIcuBugs) this.checkIcuBugs(result, isoDate);
-
+    if (this.checkIcuBugs) this.checkIcuBugs(isoDate);
     const calendarDate = this.adjustCalendarDate(result, cache, 'constrain', true);
     if (calendarDate.year === undefined) throw new RangeError(`Missing year converting ${JSON.stringify(isoDate)}`);
     if (calendarDate.month === undefined) throw new RangeError(`Missing month converting ${JSON.stringify(isoDate)}`);
@@ -597,7 +597,7 @@ const nonIsoHelperBase = {
     return calendarDate;
   },
   validateCalendarDate(calendarDate) {
-    let { era, month, year, day, eraYear, monthCode, monthExtra } = calendarDate;
+    const { era, month, year, day, eraYear, monthCode, monthExtra } = calendarDate;
     // When there's a suffix (e.g. "5bis" for a leap month in Chinese calendar)
     // the derived class must deal with it.
     if (monthExtra !== undefined) throw new RangeError('Unexpected `monthExtra` value');
@@ -1283,7 +1283,7 @@ const helperIndian = ObjectAssign({}, nonIsoHelperBase, {
   // expected.
   vulnerableToBceBug:
     new Date('0000-01-01T00:00Z').toLocaleDateString('en-US-u-ca-indian', { timeZone: 'UTC' }) !== '10/11/-79 Saka',
-  checkIcuBugs(calendarDate, isoDate) {
+  checkIcuBugs(isoDate) {
     if (this.vulnerableToBceBug && isoDate.year < 1) {
       throw new RangeError(
         `calendar '${this.id}' is broken for ISO dates before 0001-01-01` +
@@ -1384,7 +1384,7 @@ function adjustEras(eras) {
   // Ensure that the latest epoch is first in the array. This lets us try to
   // match eras in index order, with the last era getting the remaining older
   // years. Any reverse-signed era must be at the end.
-  eras.sort((e1, e2) => {
+  ArraySort.call(eras, (e1, e2) => {
     if (e1.reverseOf) return 1;
     if (e2.reverseOf) return -1;
     return e2.isoEpoch.year - e1.isoEpoch.year;
@@ -1521,7 +1521,7 @@ const makeHelperGregorian = (id, originalEras) => {
       .toLocaleDateString('en-US-u-ca-japanese', { timeZone: 'UTC' })
       .startsWith('12'),
     calendarIsVulnerableToJulianBug: false,
-    checkIcuBugs(calendarDate, isoDate) {
+    checkIcuBugs(isoDate) {
       if (this.calendarIsVulnerableToJulianBug && this.v8IsVulnerableToJulianBug) {
         const beforeJulianSwitch = ES.CompareISODate(isoDate.year, isoDate.month, isoDate.day, 1582, 10, 15) < 0;
         if (beforeJulianSwitch) {
@@ -1793,7 +1793,7 @@ const helperChinese = ObjectAssign({}, nonIsoHelperBase, {
         if (
           month === undefined &&
           monthCode.endsWith('L') &&
-          !['M01L', 'M12L', 'M13L'].includes(monthCode) &&
+          !ArrayIncludes.call(['M01L', 'M12L', 'M13L'], monthCode) &&
           overflow === 'constrain'
         ) {
           let withoutML = monthCode.slice(1, -1);
@@ -1831,7 +1831,7 @@ const helperChinese = ObjectAssign({}, nonIsoHelperBase, {
         const months = this.getMonthList(year, cache);
         let numberPart = monthCode.replace('L', 'bis').slice(1);
         if (numberPart[0] === '0') numberPart = numberPart.slice(1);
-        let monthInfo = months[numberPart];
+        const monthInfo = months[numberPart];
         if (!monthInfo) throw new RangeError(`Unmatched monthCode ${monthCode} in Chinese year ${year}`);
         if (month !== monthInfo.monthIndex) {
           throw new RangeError(`monthCode ${monthCode} doesn't correspond to month ${month} in Chinese year ${year}`);
@@ -1909,7 +1909,7 @@ const nonIsoGeneralImpl = {
     return result;
   },
   fields(fields) {
-    if (fields.includes('year')) fields = [...fields, 'era', 'eraYear'];
+    if (ArrayIncludes.call(fields, 'year')) fields = [...fields, 'era', 'eraYear'];
     return fields;
   },
   mergeFields(fields, additionalFields) {