Casts can't use "ref()" for property name

[lachlankrautz]

When defining property casts using ref() causes an infinite loop.

/**
 * @property string $my_property_name
 */
class Flim extends DataTransferObject
{
  public static function casts(): array
  {
    return [
      // ref() tries to load the class property data with includes a call to this method to 
      // get the casts and loops infinitely.
      self::ref()->my_property_name => new MyPropertyCast(),
    ];
  }
}

For now just use a string literal.

/**
 * @property string $my_property_name
 */
class Flim extends DataTransferObject
{
  public static function casts(): array
  {
    return [
      // this is safe
      'my_property_name' => new MyPropertyCast(),
    ];
  }
}