Ticket #45329: 45329.diff

src/wp-includes/link-template.php

@@ -257 +257 @@
  * @param int|WP_Post $id        Optional. Post ID or post object. Default is the global `$post`.
  * @param bool        $leavename Optional, defaults to false. Whether to keep post name. Default false.
  * @param bool        $sample    Optional, defaults to false. Is it a sample permalink. Default false.
- * @return string|WP_Error The post permalink.
+ * @return string|null The post permalink.
  */
 function get_post_permalink( $id = 0, $leavename = false, $sample = false ) {
         global $wp_rewrite;
@@ -264 +264 @@
 
         $post = get_post( $id );
 
-        if ( is_wp_error( $post ) ) {
+        if ( ! ( $post instanceof WP_Post ) ) {
                 return $post;
         }