<?php
namespace Bundle\Entity;

use Doctrine\ORM\Mapping as ORM;
use Bundle\Entity\X;
use Symfony\Component\Validator\Constraints as Assert;

/**
 * @ORM\Entity
 */
class Y
{
    /**
     * @ORM\Column(name="email", type="string", nullable=true)
     * @Assert\Email()
     * @var string
     */
    protected $email;
    /**
     * @var X $x
     */
    protected $x;
}