title: Swift - expected '{' to start setter definition
body: <p>I'm following the advanced swift WWDC 2014 video, using a subscript on a class to delegate down to a class property but I'm getting an error using the same syntax as in the video</p>
  
  <pre><code>enum Direction {
      case North, South, East, West
  }
  
  class Place: Thing {
      init (_ location: Thing?, _ name: String, _ longDescription: String) {
          self.exits = Dictionary&lt;Direction, Place&gt; ()
          super.init(location, name, longDescription)
      }
      var exits: Dictionary&lt;Direction, Place&gt;
  }
  
  extension Place {
      subscript(direction: Direction) -&gt; Place? {
          get {
              return exits[direction]
          }
          set (destination: Place?) { // error here
              exits[direction] = destination
          }
      }
  }
  </code></pre>
  
  <p>The error I'm getting is</p>
  
  <pre><code>Expected '{' to start setter definition
  </code></pre>