Fix type incompatibility in some functions

Author: fabon-f

src/datetime/endOfDay.ts

@@ -5,13 +5,15 @@ import type { Temporal } from "../types.js";
  * @param dt datetime object which includes date and time info
  * @returns Temporal object which represents the end of the day
  */
-export function endOfDay(dt: Temporal.PlainDateTime): Temporal.PlainDateTime {
+export function endOfDay<DateTime extends Temporal.PlainDateTime>(
+	dt: DateTime,
+): DateTime {
 	return dt.with({
 		hour: 23,
 		minute: 59,
 		second: 59,
 		millisecond: 999,
 		microsecond: 999,
 		nanosecond: 999,
-	});
+	}) as DateTime;
 }

src/datetime/fromJulianDate.ts

@@ -8,9 +8,11 @@ import { fromModifiedJulianDate } from "./fromModifiedJulianDate.js";
  * @param Instant `Temporal.Instant` class
  * @returns `Temporal.Instant` which corresponds to the given julian date
  */
-export function fromJulianDate(
+export function fromJulianDate<
+	InstantClassType extends typeof Temporal.Instant,
+>(
 	julianDate: number,
-	Instant: typeof Temporal.Instant,
-): Temporal.Instant {
+	Instant: InstantClassType,
+): InstanceType<InstantClassType> {
 	return fromModifiedJulianDate(julianDate - 2400000.5, Instant);
 }

src/datetime/fromModifiedJulianDate.ts

@@ -7,16 +7,18 @@ import type { Temporal } from "../types.js";
  * @param Instant `Temporal.Instant` class
  * @returns `Temporal.Instant` which corresponds to the given modified julian date
  */
-export function fromModifiedJulianDate(
+export function fromModifiedJulianDate<
+	InstantClassType extends typeof Temporal.Instant,
+>(
 	modifiedJulianDate: number,
-	Instant: typeof Temporal.Instant,
-): Temporal.Instant {
+	Instant: InstantClassType,
+): InstanceType<InstantClassType> {
 	const modifiedJulianDayInt = Math.floor(modifiedJulianDate);
 	const nanoseconds = Math.floor(
 		(modifiedJulianDate - modifiedJulianDayInt) * 8.64e13,
 	);
 	return Instant.from("1858-11-17T00:00:00Z").add({
 		hours: modifiedJulianDayInt * 24,
 		nanoseconds,
-	});
+	}) as InstanceType<InstantClassType>;
 }

src/datetime/startOfDay.ts

@@ -5,13 +5,15 @@ import type { Temporal } from "../types.js";
  * @param dt datetime object which includes date and time info
  * @returns Temporal object which represents the start of a day
  */
-export function startOfDay(dt: Temporal.PlainDateTime): Temporal.PlainDateTime {
+export function startOfDay<DateTime extends Temporal.PlainDateTime>(
+	dt: DateTime,
+): DateTime {
 	return dt.with({
 		hour: 0,
 		minute: 0,
 		second: 0,
 		millisecond: 0,
 		microsecond: 0,
 		nanosecond: 0,
-	});
+	}) as DateTime;
 }