Switched from parent type hard-coded FQCN to ::class keyword.

src/Symfony/Bridge/Doctrine/Form/Type/DoctrineType.php

@@ -22,6 +22,7 @@ use Symfony\Bridge\Doctrine\Form\EventListener\MergeDoctrineCollectionListener;
 use Symfony\Component\Form\AbstractType;
 use Symfony\Component\Form\ChoiceList\Factory\CachingFactoryDecorator;
 use Symfony\Component\Form\Exception\RuntimeException;
+use Symfony\Component\Form\Extension\Core\Type\ChoiceType;
 use Symfony\Component\Form\FormBuilderInterface;
 use Symfony\Component\OptionsResolver\Options;
 use Symfony\Component\OptionsResolver\OptionsResolver;
@@ -274,7 +275,7 @@ abstract class DoctrineType extends AbstractType implements ResetInterface
 
     public function getParent()
     {
-        return 'Symfony\Component\Form\Extension\Core\Type\ChoiceType';
+        return ChoiceType::class;
     }
 
     public function reset()

src/Symfony/Component/Form/AbstractType.php

@@ -11,6 +11,7 @@
 
 namespace Symfony\Component\Form;
 
+use Symfony\Component\Form\Extension\Core\Type\FormType;
 use Symfony\Component\Form\Util\StringUtil;
 use Symfony\Component\OptionsResolver\OptionsResolver;
 
@@ -60,6 +61,6 @@ abstract class AbstractType implements FormTypeInterface
      */
     public function getParent()
     {
-        return 'Symfony\Component\Form\Extension\Core\Type\FormType';
+        return FormType::class;
     }
 }

src/Symfony/Component/Form/Tests/Fixtures/ChoiceSubType.php

@@ -12,6 +12,7 @@
 namespace Symfony\Component\Form\Tests\Fixtures;
 
 use Symfony\Component\Form\AbstractType;
+use Symfony\Component\Form\Extension\Core\Type\ChoiceType;
 use Symfony\Component\OptionsResolver\OptionsResolver;
 
 /**
@@ -38,6 +39,6 @@ class ChoiceSubType extends AbstractType
      */
     public function getParent(): ?string
     {
-        return 'Symfony\Component\Form\Extension\Core\Type\ChoiceType';
+        return ChoiceType::class;
     }
 }