title: Swift Playground - "Use of unresolved identifier 'myClass'" but still compiles
body: <p>I am currently experimenting in Swift Playgrounds, and am trying out SpriteKit. My playground is working as expected, and runs, but Xcode has an error saying "Use of unresolved identifier 'myClass'". The playground still runs perfectly still though.</p>
  
  <p>Here is my code:</p>
  
  <pre><code>import UIKit
  import PlaygroundSupport
  import SpriteKit
  let frame = CGRect(x: 0, y: 0, width: 800, height: 600)
  let mySKScene = myClass()
  let view = SKView(frame: frame)
  view.presentScene(mySKScene)
  
  PlaygroundPage.current.liveView = view
  
  class myClass: SKScene {
      override func didMove(to view: SKView) {
  
      }
  }
  </code></pre>
  
  <p>Thanks in advance for any help.</p>
  
  <p>P.S. I am using the iOS SKD</p>