feat: Support specifying type of data_class in forms

extension.neon

@@ -34,13 +34,15 @@ parameters:
 		- stubs/Symfony/Component/EventDispatcher/EventDispatcherInterface.stub
 		- stubs/Symfony/Component/EventDispatcher/EventSubscriberInterface.stub
 		- stubs/Symfony/Component/EventDispatcher/GenericEvent.stub
+		- stubs/Symfony/Component/Form/AbstractType.stub
 		- stubs/Symfony/Component/Form/ChoiceList/Loader/ChoiceLoaderInterface.stub
 		- stubs/Symfony/Component/Form/Exception/ExceptionInterface.stub
 		- stubs/Symfony/Component/Form/Exception/RuntimeException.stub
 		- stubs/Symfony/Component/Form/Exception/TransformationFailedException.stub
 		- stubs/Symfony/Component/Form/DataTransformerInterface.stub
 		- stubs/Symfony/Component/Form/FormBuilderInterface.stub
 		- stubs/Symfony/Component/Form/FormInterface.stub
+		- stubs/Symfony/Component/Form/FormFactoryInterface.stub
 		- stubs/Symfony/Component/Form/FormTypeExtensionInterface.stub
 		- stubs/Symfony/Component/Form/FormTypeInterface.stub
 		- stubs/Symfony/Component/Form/FormView.stub
@@ -50,6 +52,7 @@ parameters:
 		- stubs/Symfony/Component/HttpFoundation/Session.stub
 		- stubs/Symfony/Component/Messenger/StampInterface.stub
 		- stubs/Symfony/Component/Messenger/Envelope.stub
+		- stubs/Symfony/Component/OptionsResolver/Exception/InvalidOptionsException.stub
 		- stubs/Symfony/Component/OptionsResolver/Options.stub
 		- stubs/Symfony/Component/Process/Process.stub
 		- stubs/Symfony/Component/PropertyAccess/PropertyPathInterface.stub

stubs/Symfony/Component/Form/AbstractType.stub

@@ -0,0 +1,12 @@
+<?php
+
+namespace Symfony\Component\Form;
+
+/**
+ * @template TData
+ *
+ * @implements FormTypeInterface<TData>
+ */
+abstract class AbstractType implements FormTypeInterface
+{
+}

stubs/Symfony/Component/Form/FormFactoryInterface.stub

@@ -0,0 +1,36 @@
+<?php
+
+namespace Symfony\Component\Form;
+
+use Symfony\Component\Form\Extension\Core\Type\FormType;
+
+interface FormFactoryInterface
+{
+	/**
+	 * @template TFormType of FormTypeInterface<TData>
+	 * @template TData
+	 *
+	 * @param class-string<TFormType> $type
+	 * @param TData $data
+	 * @param array<string, mixed> $options
+	 *
+	 * @phpstan-return ($data is null ? FormInterface<null|TData> : FormInterface<TData>)
+	 *
+	 * @throws \Symfony\Component\OptionsResolver\Exception\InvalidOptionsException
+	 */
+	public function create(string $type = FormType::class, $data = null, array $options = []): FormInterface;
+
+	/**
+	 * @template TFormType of FormTypeInterface<TData>
+	 * @template TData
+	 *
+	 * @param class-string<TFormType> $type
+	 * @param TData $data
+	 * @param array<string, mixed> $options
+     *
+     * @phpstan-return ($data is null ? FormInterface<null|TData> : FormInterface<TData>)
+	 *
+	 * @throws \Symfony\Component\OptionsResolver\Exception\InvalidOptionsException
+	 */
+	public function createNamed(string $name, string $type = FormType::class, $data = null, array $options = []): FormInterface;
+}

stubs/Symfony/Component/Form/FormInterface.stub

@@ -3,10 +3,15 @@
 namespace Symfony\Component\Form;
 
 /**
- * @extends \ArrayAccess<string, \Symfony\Component\Form\FormInterface>
- * @extends \Traversable<string, \Symfony\Component\Form\FormInterface>
+ * @template TData
+ *
+ * @extends \ArrayAccess<string, \Symfony\Component\Form\FormInterface<mixed>>
+ * @extends \Traversable<string, \Symfony\Component\Form\FormInterface<mixed>>
  */
 interface FormInterface extends \ArrayAccess, \Traversable, \Countable
 {
-
+    /**
+     * @return TData
+     */
+    public function getData();
 }

stubs/Symfony/Component/Form/FormTypeExtensionInterface.stub

@@ -2,6 +2,9 @@
 
 namespace Symfony\Component\Form;
 
+/**
+ * @template TData
+ */
 interface FormTypeExtensionInterface
 {
     /**
@@ -10,11 +13,13 @@ interface FormTypeExtensionInterface
     public function buildForm(FormBuilderInterface $builder, array $options): void;
 
     /**
+     * @phpstan-param FormInterface<TData> $form
      * @param array<string, mixed> $options
      */
     public function buildView(FormView $view, FormInterface $form, array $options): void;
 
     /**
+     * @phpstan-param FormInterface<TData> $form
      * @param array<string, mixed> $options
      */
     public function finishView(FormView $view, FormInterface $form, array $options): void;

stubs/Symfony/Component/Form/FormTypeInterface.stub

@@ -2,6 +2,9 @@
 
 namespace Symfony\Component\Form;
 
+/**
+ * @template TData
+ */
 interface FormTypeInterface
 {
     /**
@@ -10,11 +13,13 @@ interface FormTypeInterface
     public function buildForm(FormBuilderInterface $builder, array $options): void;
 
     /**
+     * @phpstan-param FormInterface<TData> $form
      * @param array<string, mixed> $options
      */
     public function buildView(FormView $view, FormInterface $form, array $options): void;
 
     /**
+     * @phpstan-param FormInterface<TData> $form
      * @param array<string, mixed> $options
      */
     public function finishView(FormView $view, FormInterface $form, array $options): void;

stubs/Symfony/Component/OptionsResolver/Exception/InvalidOptionsException.stub

@@ -0,0 +1,7 @@
+<?php
+
+namespace Symfony\Component\OptionsResolver\Exception;
+
+class InvalidOptionsException extends \InvalidArgumentException
+{
+}

tests/Stubs/Symfony/Component/Form/DataClass.php

@@ -0,0 +1,14 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Stubs\Symfony\Component\Form;
+
+class DataClass
+{
+
+	/** @var int */
+	public $foo;
+
+	/** @var string */
+	public $bar;
+
+}

tests/Stubs/Symfony/Component/Form/DataClassType.php

@@ -0,0 +1,34 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Stubs\Symfony\Component\Form;
+
+use Symfony\Component\Form\AbstractType;
+use Symfony\Component\Form\Extension\Core\Type\NumberType;
+use Symfony\Component\Form\Extension\Core\Type\TextType;
+use Symfony\Component\Form\FormBuilderInterface;
+use Symfony\Component\OptionsResolver\OptionsResolver;
+
+/**
+ * @extends AbstractType<DataClass>
+ */
+class DataClassType extends AbstractType
+{
+
+	public function buildForm(FormBuilderInterface $builder, array $options): void
+	{
+		$builder
+			->add('foo', NumberType::class)
+			->add('bar', TextType::class)
+		;
+	}
+
+	public function configureOptions(OptionsResolver $resolver): void
+	{
+		$resolver
+			->setDefaults([
+				'data_class' => DataClass::class,
+			])
+		;
+	}
+
+}

tests/Stubs/Symfony/Component/Form/FormFactoryAwareClass.php

@@ -0,0 +1,42 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Stubs\Symfony\Component\Form;
+
+use Symfony\Component\Form\FormFactoryInterface;
+
+class FormFactoryAwareClass
+{
+
+	/** @var FormFactoryInterface */
+	private $formFactory;
+
+	public function __construct(FormFactoryInterface $formFactory)
+	{
+		$this->formFactory = $formFactory;
+	}
+
+	public function doSomething(): void
+	{
+		$form = $this->formFactory->create(DataClassType::class, new DataClass());
+		$data = $form->getData();
+		$this->thisOnlyAcceptsDataClass($data);
+		$this->thisOnlyAcceptsDataClassOrNull($data);
+	}
+
+	public function doSomethingNullable(): void
+	{
+		$form = $this->formFactory->create(DataClassType::class);
+		$data = $form->getData();
+		// $this->thisOnlyAcceptsDataClass($data); // ERROR!
+		$this->thisOnlyAcceptsDataClassOrNull($data);
+	}
+
+	private function thisOnlyAcceptsDataClass(DataClass $data): void
+	{
+	}
+
+	private function thisOnlyAcceptsDataClassOrNull(?DataClass $data): void
+	{
+	}
+
+}