Additional little check to show how we're assumign the User object is the User entity

Author: weaverryan

cookbook/security/voters_data_permission.rst

@@ -118,6 +118,13 @@ edit a particular object. Here's an example implementation::
                 return VoterInterface::ACCESS_DENIED;
             }
 
+            // double-check that our User object is the entity we expect.
+            // It always will be, unless we've configured our security system
+            // in some other way.
+            if (!$user instanceof User) {
+                throw new \LogicException('The user is somehow not our User class!');
+            }
+
             switch($attribute) {
                 case self::VIEW:
                     // the data object could have for example a method isPrivate()