Boolean.php

1. 8.x drupal/core/lib/Drupal/Core/TypedData/Type/Boolean.php
2. 8.x drupal/core/vendor/easyrdf/easyrdf/lib/EasyRdf/Literal/Boolean.php
3. 8.x drupal/core/modules/views/lib/Drupal/views/Plugin/views/field/Boolean.php

<?php

/**
 * @file
 * Contains \Drupal\Core\TypedData\Type\Boolean.
 */
namespace Drupal\Core\TypedData\Type;

use Drupal\Core\TypedData\TypedData;

/**
 * The boolean data type.
 *
 * The plain value of a boolean is a regular PHP boolean. For setting the value
 * any PHP variable that casts to a boolean may be passed.
 */
class Boolean extends TypedData {

  /**
   * The data value.
   *
   * @var boolean
   */
  protected $value;

}