title: Xcode 11 Beta 3, build error "Unknown attribute 'State'", "Use of undeclared type 'View'" etc
body: <p>I build an app with the 2nd beta of Xcode 11, using SwiftUI, and everything worked completely fine, but now, with the 3rd beta, the app isn't even build. I get errors like "Use of undeclared type 'View'", "Unknown attribute 'State'" etc. What can I do? Is the problem in my code or is it just a bug?</p>
  
  <p><strong>The problem is when I'm trying to build the app to run on my Mac (with UIKit for Mac)</strong></p>
  
  <pre class="lang-swift prettyprint-override"><code>@State var score = 0
  </code></pre>
  
  <p>The error is "Unknown attribute 'State'"</p>
  
  <pre class="lang-swift prettyprint-override"><code>struct ContentView : View {
      /*...*/
  }
  </code></pre>
  
  <p>The error is "Use of undeclared type 'View'"</p>