Both usage of `abstract` and `returns` properties

Hello!
I want to declare interface of abstract function, but I have a problem with both usage of `abstract` and `returns` properties.

``` js
Redundant return statement at ./code.js :
   476 |     * @abstract
   477 |     * @returns {Number}
---------------^
   478 |     */
   479 |    getPopupWidth: function() {},
```

It is bug?
