title: NSMutableDictionary: Cast to unrelated Swift type?
body: <p>Can anyone help me out with the correct way round this, I have tried various versions but always hit either an error or a warning. The code and output below are from a Swift Playground.</p>
  
  <pre><code>var foundationDict = NSMutableDictionary()
  foundationDict.setObject("Bilbo", forKey: "FirstName")
  foundationDict.setObject("Baggins", forKey: "LastName")
  
  var swiftDict = foundationDict as! Dictionary&lt;String, String&gt;
  for (key, value) in swiftDict {
      print("KEY: \(key) VALUE: |\(value)")
  }
  </code></pre>
  
  <p>OUTPUT:</p>
  
  <pre><code>KEY: FirstName VALUE: |Bilbo
  KEY: LastName VALUE: |Baggins
  </code></pre>
  
  <p>WARNING:</p>
  
  <pre><code>Cast from NSMutableDictionary to unrelated type Dictionary&lt;String String&gt; always fails
  </code></pre>