title: Type 'UILayoutPriority' has no member 'defaultHigh'
body: <p>When using this code in our app, we run into an error:</p>
  
  <pre><code>let value = UILayoutPriority.defaultHigh // Error: Type 'UILayoutPriority' has no member 'defaultHigh'. 
  </code></pre>
  
  <p>which is super wired because according to the documentation, it is obviously there. And also, if we click through <code>UILayoutPriority</code> and jump to its definition, we see it there as well. </p>
  
  <p><strong>UIKit</strong> > <strong>NSLayoutConstraint</strong>: </p>
  
  <pre><code>extension UILayoutPriority {
  
      @available(iOS 6.0, *)
      public static let required: UILayoutPriority
  </code></pre>
  
  <p>So why we cannot use <code>UILayoutPriority.defaultHigh</code>? </p>