Fix more specific return type hints for some ext/date methods

Ideally, these methods should have been declared with a static return type, so let's add a PHPDoc type hint + a TODO for fixing the issue in the future.

Author: kocsismate

ext/date/php_date.stub.php

@@ -225,10 +225,14 @@ public function __wakeup(): void {}
     /** @tentative-return-type */
     public static function __set_state(array $array): DateTime {}
 
-    /** @tentative-return-type */
-    public static function createFromImmutable(DateTimeImmutable $object): DateTime {}
+    /**
+     * @tentative-return-type
+     * @return static
+     */
+    public static function createFromImmutable(DateTimeImmutable $object): DateTime {} // TODO return type should be static
 
-    public static function createFromInterface(DateTimeInterface $object): DateTime {}
+    /** @return static */
+    public static function createFromInterface(DateTimeInterface $object): DateTime {} // TODO return type should be static
 
     /**
      * @tentative-return-type
@@ -403,10 +407,14 @@ public function setISODate(int $year, int $week, int $dayOfWeek = 1): DateTimeIm
     /** @tentative-return-type */
     public function setTimestamp(int $timestamp): DateTimeImmutable {}
 
-    /** @tentative-return-type */
-    public static function createFromMutable(DateTime $object): DateTimeImmutable {}
+    /**
+     * @tentative-return-type
+     * @return static
+     */
+    public static function createFromMutable(DateTime $object): DateTimeImmutable {} // TODO return type should be static
 
-    public static function createFromInterface(DateTimeInterface $object): DateTimeImmutable {}
+    /** @return static */
+    public static function createFromInterface(DateTimeInterface $object): DateTimeImmutable {} // TODO return type should be static
 }
 
 class DateTimeZone

ext/date/php_date_arginfo.h

@@ -1,5 +1,5 @@
 /* This is a generated file, edit the .stub.php file instead.
- * Stub hash: db6fd5b6c366dd8ee48ead99d235baa86e564401 */
+ * Stub hash: 86c6321ad1dc6f0efe94669dc6fd759752c32302 */
 
 ZEND_BEGIN_ARG_WITH_RETURN_TYPE_MASK_EX(arginfo_strtotime, 0, 1, MAY_BE_LONG|MAY_BE_FALSE)
 	ZEND_ARG_TYPE_INFO(0, datetime, IS_STRING, 0)