Constraint.php

<?php

namespace Drupal\Core\Validation\Annotation;

use Drupal\Component\Annotation\Plugin;

/**
 * Defines a validation constraint annotation object.
 *
 * Plugin Namespace: Plugin\Validation\Constraint
 *
 * For a working example, see
 * \Drupal\Core\Validation\Plugin\Validation\Constraint\LengthConstraint
 *
 * @see \Drupal\Core\Validation\ConstraintManager
 * @see \Symfony\Component\Validator\Constraint
 * @see hook_validation_constraint_alter()
 * @see plugin_api
 *
 * @Annotation
 */
class Constraint extends Plugin {
    
    /**
     * The constraint plugin ID.
     *
     * @var string
     */
    public $id;
    
    /**
     * The human-readable name of the constraint plugin.
     *
     * @var string|\Drupal\Core\Annotation\Translation
     *
     * @ingroup plugin_translatable
     */
    public $label;
    
    /**
     * DataType plugin IDs for which this constraint applies.
     *
     * Valid values are any types registered by the typed data API, or an array
     * of multiple type names. For supporting all types, FALSE may be specified.
     * The key defaults to an empty array, which indicates no types are supported.
     *
     * @var string|string[]|false
     *
     * @see \Drupal\Core\TypedData\Annotation\DataType
     */
    public $type = [];

}