Symfony2:默认表单类型Guesser已损坏

我设法打破了symfony 2.6的默认表单类型guesser。让我给你看一些简单的代码：

示例类型.php

namespace AppBundle'Form;
use Symfony'Component'Form'AbstractType;
use Symfony'Component'Form'FormBuilderInterface;
use Symfony'Component'OptionsResolver'OptionsResolverInterface;
class ExampleType extends AbstractType
{
    /**
     * @param FormBuilderInterface $builder
     * @param array $options
     */
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder
            ->add('test')  // should be a text type because it's stored as string
        ;
    }
    ...
}

但是当我调用表单时，我得到一个未捕获的PHP异常：

Symfony'Component'Form'Exception'InvalidArgumentException: "Could not load type "Symfony'Component'Form'Extension'Core'Type'TextType"" at /home/gv/PhpstormProjects/vcb/vendor/symfony/symfony/src/Symfony/Component/Form/FormRegistry.php line 83 

堆栈跟踪：

[1] Symfony'Component'Form'Exception'InvalidArgumentException: Could not load type "Symfony'Component'Form'Extension'Core'Type'TextType"
at n/a
    in /home/gv/PhpstormProjects/vcb/vendor/symfony/symfony/src/Symfony/Component/Form/FormRegistry.php line 83
at Symfony'Component'Form'FormRegistry->getType('Symfony'Component'Form'Extension'Core'Type'TextType')
    in /home/gv/PhpstormProjects/vcb/vendor/symfony/symfony/src/Symfony/Component/Form/FormFactory.php line 82
at Symfony'Component'Form'FormFactory->createNamedBuilder('test', 'Symfony'Component'Form'Extension'Core'Type'TextType', null, array('required' => false))
    in /home/gv/PhpstormProjects/vcb/vendor/symfony/symfony/src/Symfony/Component/Form/FormFactory.php line 132
at Symfony'Component'Form'FormFactory->createBuilderForProperty('AppBundle'Entity'Example', 'test', null, array())
    in /home/gv/PhpstormProjects/vcb/vendor/symfony/symfony/src/Symfony/Component/Form/FormBuilder.php line 109
at Symfony'Component'Form'FormBuilder->create('test', null, array())
    in /home/gv/PhpstormProjects/vcb/vendor/symfony/symfony/src/Symfony/Component/Form/FormBuilder.php line 267
at Symfony'Component'Form'FormBuilder->resolveChildren()
    in /home/gv/PhpstormProjects/vcb/vendor/symfony/symfony/src/Symfony/Component/Form/FormBuilder.php line 215
at Symfony'Component'Form'FormBuilder->getForm()
    in /home/gv/PhpstormProjects/vcb/vendor/symfony/symfony/src/Symfony/Component/Form/FormFactory.php line 39

通过显式传递表单类型作为第二个参数（在本例中为"text"）来规避此异常是没有问题的，但我想知道是什么会阻止默认表单类型guesser正常工作。

有什么建议吗？

Greg