Polyfill: Implement previous commit in reference code

Brings the reference code in line with the editorial changes in the spec
text from the previous commit.

polyfill/lib/duration.mjs

@@ -38,6 +38,7 @@ import {
   SetSlot,
   TIME_ZONE
 } from './slots.mjs';
+import { TimeDuration } from './timeduration.mjs';
 
 export class Duration {
   constructor(
@@ -282,9 +283,20 @@ export class Duration {
       throw new RangeErrorCtor(`a starting point is required for ${largestUnit}s balancing`);
     }
     assert(!ES.IsCalendarUnit(smallestUnit), 'smallestUnit was larger than largestUnit');
-    let duration = ES.ToInternalDurationRecordWith24HourDays(this);
-    duration = ES.RoundTimeDuration(duration, roundingIncrement, smallestUnit, roundingMode);
-    return ES.TemporalDurationFromInternal(duration, largestUnit);
+    let internalDuration = ES.ToInternalDurationRecordWith24HourDays(this);
+    if (smallestUnit === 'day') {
+      // First convert time units up to days
+      const DAY_NANOS = 86400 * 1e9;
+      const { quotient, remainder } = internalDuration.time.divmod(DAY_NANOS);
+      let days = internalDuration.date.days + quotient + remainder.fdiv(DAY_NANOS);
+      days = ES.RoundNumberToIncrement(days, roundingIncrement, roundingMode);
+      const dateDuration = { years: 0, months: 0, weeks: 0, days };
+      internalDuration = ES.CombineDateAndTimeDuration(dateDuration, TimeDuration.ZERO);
+    } else {
+      const timeDuration = ES.RoundTimeDuration(internalDuration.time, roundingIncrement, smallestUnit, roundingMode);
+      internalDuration = ES.CombineDateAndTimeDuration(ES.ZeroDateDuration(), timeDuration);
+    }
+    return ES.TemporalDurationFromInternal(internalDuration, largestUnit);
   }
   total(totalOf) {
     if (!ES.IsTemporalDuration(this)) throw new TypeErrorCtor('invalid receiver');
@@ -349,10 +361,11 @@ export class Duration {
     if (unit === 'nanosecond' && increment === 1) return ES.TemporalDurationToString(this, precision);
 
     const largestUnit = ES.DefaultTemporalLargestUnit(this);
-    let duration = ES.ToInternalDurationRecord(this);
-    duration = ES.RoundTimeDuration(duration, increment, unit, roundingMode);
+    let internalDuration = ES.ToInternalDurationRecord(this);
+    const timeDuration = ES.RoundTimeDuration(internalDuration.time, increment, unit, roundingMode);
+    internalDuration = ES.CombineDateAndTimeDuration(internalDuration.date, timeDuration);
     const roundedDuration = ES.TemporalDurationFromInternal(
-      duration,
+      internalDuration,
       ES.LargerOfTwoTemporalUnits(largestUnit, 'second')
     );
     return ES.TemporalDurationToString(roundedDuration, precision);

polyfill/lib/ecmascript.mjs

@@ -778,7 +778,7 @@ export function AdjustDateDurationRecord({ years, months, weeks, days }, newDays
   };
 }
 
-function ZeroDateDuration() {
+export function ZeroDateDuration() {
   return { years: 0, months: 0, weeks: 0, days: 0 };
 }
 
@@ -2952,7 +2952,7 @@ export function TemporalDurationFromInternal(internalDuration, largestUnit) {
   );
 }
 
-function CombineDateAndTimeDuration(dateDuration, timeDuration) {
+export function CombineDateAndTimeDuration(dateDuration, timeDuration) {
   const dateSign = DateDurationSign(dateDuration);
   const timeSign = timeDuration.sign();
   if (dateSign !== 0 && timeSign !== 0 && dateSign !== timeSign) {
@@ -2994,8 +2994,9 @@ function DifferenceTime(time1, time2) {
 }
 
 function DifferenceInstant(ns1, ns2, increment, smallestUnit, roundingMode) {
-  const diff = { date: ZeroDateDuration(), time: TimeDuration.fromEpochNsDiff(ns2, ns1) };
-  return RoundTimeDuration(diff, increment, smallestUnit, roundingMode);
+  let timeDuration = TimeDuration.fromEpochNsDiff(ns2, ns1);
+  timeDuration = RoundTimeDuration(timeDuration, increment, smallestUnit, roundingMode);
+  return CombineDateAndTimeDuration(ZeroDateDuration(), timeDuration);
 }
 
 function DifferenceISODateTime(isoDateTime1, isoDateTime2, calendar, largestUnit) {
@@ -3691,10 +3692,13 @@ export function DifferenceTemporalPlainTime(operation, plainTime, other, options
   const settings = GetDifferenceSettings(operation, resolvedOptions, 'time', [], 'nanosecond', 'hour');
 
   let timeDuration = DifferenceTime(GetSlot(plainTime, TIME), GetSlot(other, TIME));
-  let duration = { date: ZeroDateDuration(), time: timeDuration };
-  if (settings.smallestUnit !== 'nanosecond' || settings.roundingIncrement !== 1) {
-    duration = RoundTimeDuration(duration, settings.roundingIncrement, settings.smallestUnit, settings.roundingMode);
-  }
+  timeDuration = RoundTimeDuration(
+    timeDuration,
+    settings.roundingIncrement,
+    settings.smallestUnit,
+    settings.roundingMode
+  );
+  const duration = CombineDateAndTimeDuration(ZeroDateDuration(), timeDuration);
 
   let result = TemporalDurationFromInternal(duration, settings.largestUnit);
   if (operation === 'since') result = CreateNegatedTemporalDuration(result);
@@ -4060,20 +4064,10 @@ export function RoundTime(
   }
 }
 
-export function RoundTimeDuration(duration, increment, unit, roundingMode) {
-  // unit must not be a calendar unit
-  if (unit === 'day') {
-    // First convert time units up to days
-    const { quotient, remainder } = duration.time.divmod(DAY_NANOS);
-    let days = duration.date.days + quotient + remainder.fdiv(DAY_NANOS);
-    days = RoundNumberToIncrement(days, increment, roundingMode);
-    const dateDuration = AdjustDateDurationRecord(duration.date, days);
-    return CombineDateAndTimeDuration(dateDuration, TimeDuration.ZERO);
-  }
-
+export function RoundTimeDuration(timeDuration, increment, unit, roundingMode) {
+  // unit must be a time unit
   const divisor = Call(MapPrototypeGet, NS_PER_TIME_UNIT, [unit]);
-  const timeDuration = duration.time.round(divisor * increment, roundingMode);
-  return CombineDateAndTimeDuration(duration.date, timeDuration);
+  return timeDuration.round(divisor * increment, roundingMode);
 }
 
 export function TotalTimeDuration(timeDuration, unit) {