[Form] fix return type on FormDataCollector

src/Symfony/Component/Form/Extension/DataCollector/FormDataCollectorInterface.php

@@ -14,6 +14,7 @@ namespace Symfony\Component\Form\Extension\DataCollector;
 use Symfony\Component\Form\FormInterface;
 use Symfony\Component\Form\FormView;
 use Symfony\Component\HttpKernel\DataCollector\DataCollectorInterface;
+use Symfony\Component\VarDumper\Cloner\Data;
 
 /**
  * Collects and structures information about forms.
@@ -78,7 +79,7 @@ interface FormDataCollectorInterface extends DataCollectorInterface
     /**
      * Returns all collected data.
      *
-     * @return array
+     * @return array|Data
      */
     public function getData();
 }

src/Symfony/Component/HttpKernel/DataCollector/DataCollector.php

@@ -28,6 +28,9 @@ use Symfony\Component\VarDumper\Cloner\VarCloner;
  */
 abstract class DataCollector implements DataCollectorInterface, \Serializable
 {
+    /**
+     * @var array|Data
+     */
     protected $data = [];
 
     /**