Editorial: Return Time Record from ToTemporalTimeOrMidnight, and rename

This avoids creation of an unobservable Temporal.PlainTime object, and is
also simpler to read. Since it no longer returns a Temporal object, give
it a more appropriate name.

UPSTREAM_COMMIT=dd9679fea7db0130738cf8636b47d2eb67e4afe9

Author: ptomato

lib/ecmascript.ts

@@ -1687,10 +1687,9 @@ export function ToTemporalTime(item: PlainTimeParams['from'][0], options?: Plain
   return CreateTemporalTime(time);
 }
 
-export function ToTemporalTimeOrMidnight(item: string | Temporal.PlainTime | Temporal.PlainTimeLike | undefined) {
-  const TemporalPlainTime = GetIntrinsic('%Temporal.PlainTime%');
-  if (item === undefined) return new TemporalPlainTime();
-  return ToTemporalTime(item);
+export function ToTimeRecordOrMidnight(item: PlainTimeParams['from'][0] | undefined) {
+  if (item === undefined) return MidnightTimeRecord();
+  return GetSlot(ToTemporalTime(item), TIME);
 }
 
 export function ToTemporalYearMonth(

lib/plaindate.ts

@@ -173,10 +173,10 @@ export class PlainDate implements Temporal.PlainDate {
   valueOf(): never {
     ES.ValueOfThrows('PlainDate');
   }
-  toPlainDateTime(temporalTimeParam: Params['toPlainDateTime'][0] = undefined): Return['toPlainDateTime'] {
+  toPlainDateTime(temporalTime: Params['toPlainDateTime'][0] = undefined): Return['toPlainDateTime'] {
     if (!ES.IsTemporalDate(this)) throw new TypeErrorCtor('invalid receiver');
-    const temporalTime = ES.ToTemporalTimeOrMidnight(temporalTimeParam);
-    const isoDateTime = ES.CombineISODateAndTimeRecord(GetSlot(this, ISO_DATE), GetSlot(temporalTime, TIME));
+    const time = ES.ToTimeRecordOrMidnight(temporalTime);
+    const isoDateTime = ES.CombineISODateAndTimeRecord(GetSlot(this, ISO_DATE), time);
     return ES.CreateTemporalDateTime(isoDateTime, GetSlot(this, CALENDAR));
   }
   toZonedDateTime(item: Params['toZonedDateTime'][0]): Return['toZonedDateTime'] {

lib/plaindatetime.ts

@@ -3,7 +3,7 @@ import { RangeError as RangeErrorCtor, TypeError as TypeErrorCtor } from './prim
 import * as ES from './ecmascript';
 import { MakeIntrinsicClass } from './intrinsicclass';
 
-import { CALENDAR, GetSlot, ISO_DATE_TIME, TIME } from './slots';
+import { CALENDAR, GetSlot, ISO_DATE_TIME } from './slots';
 import type { Temporal } from '..';
 import { DateTimeFormat } from './intl';
 import type { PlainDateTimeParams as Params, PlainDateTimeReturn as Return } from './internaltypes';
@@ -174,13 +174,10 @@ export class PlainDateTime implements Temporal.PlainDateTime {
     const newDateTime = ES.InterpretTemporalDateTimeFields(calendar, fields, overflow);
     return ES.CreateTemporalDateTime(newDateTime, calendar);
   }
-  withPlainTime(temporalTimeParam: Params['withPlainTime'][0] = undefined): Return['withPlainTime'] {
+  withPlainTime(temporalTime: Params['withPlainTime'][0] = undefined): Return['withPlainTime'] {
     if (!ES.IsTemporalDateTime(this)) throw new TypeErrorCtor('invalid receiver');
-    const temporalTime = ES.ToTemporalTimeOrMidnight(temporalTimeParam);
-    const isoDateTime = ES.CombineISODateAndTimeRecord(
-      GetSlot(this, ISO_DATE_TIME).isoDate,
-      GetSlot(temporalTime, TIME)
-    );
+    const time = ES.ToTimeRecordOrMidnight(temporalTime);
+    const isoDateTime = ES.CombineISODateAndTimeRecord(GetSlot(this, ISO_DATE_TIME).isoDate, time);
     return ES.CreateTemporalDateTime(isoDateTime, GetSlot(this, CALENDAR));
   }
   withCalendar(calendarParam: Params['withCalendar'][0]): Return['withCalendar'] {