Add missing @return annotations to fix deprecations on PHP 8

Author: nicolas-grekas

Controller/AbstractController.php

@@ -58,7 +58,7 @@ public function setContainer(ContainerInterface $container): ?ContainerInterface
     /**
      * Gets a container parameter by its name.
      *
-     * @return mixed
+     * @return array|bool|float|int|string|null
      *
      * @final
      */

Controller/Controller.php

@@ -31,7 +31,7 @@ abstract class Controller implements ContainerAwareInterface
     /**
      * Gets a container configuration parameter by its name.
      *
-     * @return mixed
+     * @return array|bool|float|int|string|null
      *
      * @final
      */

Routing/LegacyRouteLoaderContainer.php

@@ -29,6 +29,8 @@ public function __construct(ContainerInterface $container, ContainerInterface $s
 
     /**
      * {@inheritdoc}
+     *
+     * @return mixed
      */
     public function get($id)
     {

Test/TestContainer.php

@@ -58,6 +58,8 @@ public function getParameterBag(): ParameterBagInterface
 
     /**
      * {@inheritdoc}
+     *
+     * @return array|bool|float|int|string|null
      */
     public function getParameter($name)
     {