Add DataTransformer stub

Author: VincentLanglet

extension.neon

@@ -15,6 +15,7 @@ parameters:
 		- stubs/Symfony/Component/EventDispatcher/EventDispatcherInterface.stub
 		- stubs/Symfony/Component/EventDispatcher/EventSubscriberInterface.stub
 		- stubs/Symfony/Component/EventDispatcher/GenericEvent.stub
+		- stubs/Symfony/Component/Form/DataTransformerInterface.stub
 		- stubs/Symfony/Component/Form/FormBuilderInterface.stub
 		- stubs/Symfony/Component/Form/FormInterface.stub
 		- stubs/Symfony/Component/Form/FormTypeExtensionInterface.stub

stubs/Symfony/Component/Form/DataTransformerInterface.stub

@@ -0,0 +1,26 @@
+<?php
+
+namespace Symfony\Component\Form;
+
+use Symfony\Component\Form\Exception\TransformationFailedException;
+
+/**
+ * @phpstan-template T
+ * @phpstan-template R
+ */
+interface DataTransformerInterface
+{
+    /**
+     * @phpstan-param T|null $value The value in the original representation
+     *
+     * @phpstan-return R|null The value in the transformed representation
+     */
+    public function transform($value);
+
+    /**
+     * @phpstan-param R|null $value The value in the transformed representation
+     *
+     * @phpstan-return T|null The value in the original representation
+     */
+    public function reverseTransform($value);
+}