title: Declarations in extensions cannot override yet
body: <p>I checked <a href="https://stackoverflow.com/questions/44616409/declarations-in-extensions-cannot-override-yet-error-in-swift-4">Declarations in extensions cannot override yet error in Swift 4</a></p>
  
  <p>In my case :</p>
  
  <p>I have BaseViewController like below :</p>
  
  <pre><code>class BaseViewController: UIViewController {
      func extFunction() {
          print("extFunction")
      }
  }
  </code></pre>
  
  <p>In have another view controller</p>
  
  <pre><code>class TestViewController : BaseViewController {
      override func extFunction() { // getting error in this line
          print("extFunction from TestViewController")
      }
  }
  </code></pre>
  
  <p><strong>UPDATE</strong> - I have now changed it to:</p>
  
  <pre><code>class BaseViewController: UIViewController {
      func extFunction() {
          print("extFunction")
      }
  }
  </code></pre>
  
  <p>In have another view controller</p>
  
  <pre><code>class TestViewController : BaseViewController {
      override func extFunction() { // getting error in this line
          print("extFunction from TestViewController")
      }
  }
  </code></pre>
  
  <p>Any help would be appreciated.</p>