Merge branch '6.3' into 6.4

* 6.3:
  add return types to test fixtures

Author: xabbuh

Tests/Fixtures/DummyString.php

@@ -22,7 +22,7 @@ class DummyString implements DenormalizableInterface
     /** @var string $value */
     public $value;
 
-    public function denormalize(DenormalizerInterface $denormalizer, $data, string $format = null, array $context = [])
+    public function denormalize(DenormalizerInterface $denormalizer, $data, string $format = null, array $context = []): void
     {
         $this->value = $data;
     }

Tests/Fixtures/NotNormalizableDummy.php

@@ -24,7 +24,7 @@ public function __construct()
     {
     }
 
-    public function denormalize(DenormalizerInterface $denormalizer, $data, string $format = null, array $context = [])
+    public function denormalize(DenormalizerInterface $denormalizer, $data, string $format = null, array $context = []): void
     {
         throw new NotNormalizableValueException();
     }