title: How to fix the warning of type casting in 'if let' statement in Xcode 8.3?
body: <p>Consider the following code:</p>
  
  <pre><code>let nsdate: NSDate? = NSDate()
  if let date = nsdate as? Date { // a warning occurs here
      print(date)
  }
  </code></pre>
  
  <p>The compiler complains like this: <code>Conditional downcast from 'NSDate?' to 'Date' is a bridging conversion; did you mean to use 'as'?</code></p>
  
  <p>A cast from <code>NSData</code> to <code>Data</code> has the same problem. How to fix the it?</p>