title: Swift - Use of undeclared type 'Error'
body: <p>Should not <code>Error</code> be a build in type? This:</p>
  
  <pre><code>import Foundation
  
  struct Video {
  
    struct Source {
  
      enum SourceError: Error {
        case InvalidData
        case InvalidHeight
        case InvalidURL
      }
    }
  }
  </code></pre>
  
  <p>gives me <code>Use of undeclared type 'Error'</code>.. I'm on xcode 8 beta 5</p>