Datalist in Symfony

DatalistType.php

<?php
namespace Acme\Form\Type;

use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\FormInterface;
use Symfony\Component\Form\FormView;
use Symfony\Component\OptionsResolver\OptionsResolverInterface;

class DatalistType extends AbstractType
{
    public function getParent()
    {
        return 'text';
    }

    public function setDefaultOptions(OptionsResolverInterface $resolver)
    {
        $resolver->setRequired(['choices']);
    }

    public function buildView(FormView $view, FormInterface $form, array $options)
    {
        $view->vars['choices'] = $options['choices'];
    }

    public function getName()
    {
        return 'datalist';
    }
}

fields.html.twig

{% block datalist_widget %}
  <input list="{{ id }}" {{ block('widget_attributes') }}>
    <datalist id="{{ id }}">
      {% for choice in choices %}
        <option value="{{ choice }}"></option>
      {% endfor %}
    </datalist>
{% endblock %}

FormType.php

public function buildForm(FormBuilderInterface $builder, array $options)
{
    $builder->add('country', 'datalist', [choices' => ['a', 'b']]); 
}

services.yml

form.type.datalist_type:
    class: Acme\Form\Type\DatalistType
    tags:
        -  { name: form.type, alias: datalist }