Code Modernization: Silence the deprecation warnings for missing return type in `WP_Theme`.

This fixes the "Deprecated: Return type of `WP_Theme::[METHODNAME]($offset)` should be compatible with `ArrayAccess::[METHODNAME](): type`" warnings on PHP 8.1.

PHP native interfaces now have declared return types and methods in classes implementing these interfaces need to either have the return type declared (in a covariant compatible manner with the PHP native interface method declaration), or need to silence the deprecation warning using the `#[ReturnTypeWillChange]` attribute.

Follow-up to [51517].

Props jrf.
See #53635.
Built from https://develop.svn.wordpress.org/trunk@51529


git-svn-id: http://core.svn.wordpress.org/trunk@51140 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/class-wp-theme.php

@@ -556,6 +556,7 @@ final class WP_Theme implements ArrayAccess {
 	 * @param mixed $offset
 	 * @param mixed $value
 	 */
+	#[ReturnTypeWillChange]
 	public function offsetSet( $offset, $value ) {}
 
 	/**
@@ -565,6 +566,7 @@ final class WP_Theme implements ArrayAccess {
 	 *
 	 * @param mixed $offset
 	 */
+	#[ReturnTypeWillChange]
 	public function offsetUnset( $offset ) {}
 
 	/**
@@ -575,6 +577,7 @@ final class WP_Theme implements ArrayAccess {
 	 * @param mixed $offset
 	 * @return bool
 	 */
+	#[ReturnTypeWillChange]
 	public function offsetExists( $offset ) {
 		static $keys = array(
 			'Name',
@@ -616,6 +619,7 @@ final class WP_Theme implements ArrayAccess {
 	 * @param mixed $offset
 	 * @return mixed
 	 */
+	#[ReturnTypeWillChange]
 	public function offsetGet( $offset ) {
 		switch ( $offset ) {
 			case 'Name':

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.9-alpha-51528';
+$wp_version = '5.9-alpha-51529';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.