AngularJS -CoffeeScript factory

[yuryodin]

https://github.com/Plateful/plateful-mobile/wiki/AngularJS-CoffeeScript-Style-Guide#factories
in right example

### recommended ###
(->
  dataService = ()->

    someValue = ''

    ##########

    return
      save: ()->
       # . #

      validate: ()->
       # . #
  angular
    .module('app')
    .service('dataService', dataService)
)()

Coffescript compiler shows SyntaxError 'unexpected indentation' at return line
What's wrong with that?And why topic called factories and we create "service" ?