title: Swift UnsafeMutableRawPointer Error
body: <p>With Swift 3, I got this, without any errors:</p>
  
  <pre><code>private var SessionRunningContext = 0
  
  func addObservers() {
     self.session.addObserver(self, forKeyPath: "running", options: .new, context: &amp;SessionRunningContext)
  }
  
  func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
     let newValue: AnyObject? = change![NSKeyValueChangeKey.newKey] as AnyObject?
     switch context! {
       case &amp;SessionRunningContext:
           // Do something
     }
  }
  </code></pre>
  
  <p>However, when I build this on iOS 12, Xcode Beta, I get an error saying:</p>
  
  <blockquote>
    <p>Use of extraneous '&amp;'</p>
  </blockquote>
  
  <p>for this line:</p>
  
  <pre><code>case &amp;SessionRunningContext:
  </code></pre>