Changes from @12wrigja code review comments

Author: justingrant

lib/ecmascript.ts

@@ -744,10 +744,10 @@ export function ToTemporalDateTimeRoundingIncrement(
   smallestUnit: keyof TemporalDateTimeRoundingMaximumIncrements
 ) {
   const maximumIncrements: TemporalDateTimeRoundingMaximumIncrements = {
-    year: undefined as number | undefined,
-    month: undefined as number | undefined,
-    week: undefined as number | undefined,
-    day: undefined as number | undefined,
+    year: undefined,
+    month: undefined,
+    week: undefined,
+    day: undefined,
     hour: 24,
     minute: 60,
     second: 60,
@@ -808,6 +808,21 @@ export function ToSecondsStringPrecision(options: Temporal.ToStringPrecisionOpti
   }
 }
 
+export function ToLargestTemporalUnit<Allowed extends Temporal.DateTimeUnit, Disallowed extends Temporal.DateTimeUnit>(
+  options: { largestUnit?: Temporal.LargestUnitOption<Allowed> },
+  fallback: Allowed | 'auto',
+  disallowedStrings?: ReadonlyArray<Disallowed>
+): Allowed | 'auto';
+export function ToLargestTemporalUnit<
+  Allowed extends Temporal.DateTimeUnit,
+  Disallowed extends Temporal.DateTimeUnit,
+  IfAuto extends Allowed | undefined = Allowed
+>(
+  options: { largestUnit?: Temporal.LargestUnitOption<Allowed> },
+  fallback: Allowed | 'auto',
+  disallowedStrings: ReadonlyArray<Disallowed>,
+  autoValue?: IfAuto
+): Allowed;
 export function ToLargestTemporalUnit<
   Allowed extends Temporal.DateTimeUnit,
   Disallowed extends Temporal.DateTimeUnit,
@@ -880,7 +895,8 @@ export function ToRelativeTemporalObject(options: {
     | undefined;
 }): Temporal.ZonedDateTime | Temporal.PlainDateTime | undefined {
   const relativeTo = options.relativeTo;
-  // TODO: file a bug against TypeScript because `as undefined` below should not be needed.
+  // TODO: `as undefined` below should not be needed.  Verify that it can be
+  // removed after strictNullChecks is enabled.
   if (relativeTo === undefined) return relativeTo as undefined;
 
   let offsetBehaviour: OffsetBehaviour = 'option';