title: Cannot pass immutable value of type 'NSObject' as inout argument
body: <p>This should work, but I've got no clue why it doesn't. The code is self-explanatory.</p>
  
  <pre><code>class Themer {
  
     class func applyTheme(_ object: inout NSObject) {
        //do theming
     }
  }
  </code></pre>
  
  <p>And I apply theme to the button like so:</p>
  
  <pre><code>class ViewController: UIViewController {
  
      @IBOutlet weak var button: UIButton!
      override func viewDidLoad() {
  
          super.viewDidLoad()
          Themer.applyTheme(&amp;button)
      }
  </code></pre>
  
  <p>The button object is a variable, yet the compiler throws an error.</p>