title: "Expected expression in Swift key path" Error while Refactoring code with Extensions
body: <p>I have been trying refactor code by thanking functions and adding them in a separate file <code>extension</code> of a <code>ViewController</code> </p>
  
  <p>What I have in this extension is a function that adds <code>gesture recognizers</code> to some views that have references to functions that I have placed in other file extension of the same <code>ViewController</code>. On build I am getting this error <strong><em>"Expected expression in Swift key path"</em></strong></p>
  
  <p>What is causing this error? </p>