title: updateValue not working for Dictionary
body: <p>
  I'm creating a test app using Swift in Xcode, and I've run into an annoying issue. I'm writing a simple class that will act as a cache using a Dictionary object. My implementation is below:</p>
  
  <pre class="lang-swift prettyprint-override"><code>import Foundation
  import UIKit
  
  class ImageCache {
      var dict:Dictionary&lt;String,NSData&gt;?;
  
      init() {
          dict = Dictionary&lt;String,NSData&gt;();
      }
  
      func exists(id:String) -&gt; Bool {
          return dict!.indexForKey(id)!==nil;
      }
  
      func getImage(id:String) -&gt; UIImage? {
          if(!exists(id)) {
              return nil;
          }
          return UIImage(data: (dict!)[id]);
      }
  
      func setData(id:String, data:NSData) {
          dict!.updateValue(data, forKey: id);
      }
  }
  </code></pre>
  
  <p>The issue is in the last method, with Xcode stating "Could not find member 'UpdateValue'". This is weird, because the code hint seems to show it just fine:</p>
  
  <p><img src="https://i.stack.imgur.com/ZHrfj.png" alt="Code hint"></p>
  
  <p>But when I try to compile:</p>
  
  <p><img src="https://i.stack.imgur.com/3KWPg.png" alt="Compilation error"></p>
  
  <p>Could this potentially be a bug in Xcode? Or am I missing something super-obvious?</p>