title: Getting "extraneous argument label" when trying to append array to other array in Swift
body: <p>I'm getting <code>extraneous argument label 'contentsOf:' in call
  array.append(contentsOf: test)</code> error when trying to run this code in playground:</p>
  
  <pre><code>import Cocoa
  
  var array:[Any] = []
  let test = [""]
  array.append(contentsOf: [""])
  array.append(contentsOf: test)
  </code></pre>
  
  <p>Why is this happening? As I understand, there are two equal arrays with empty string.</p>