title: Cannot convert value of type 'X' to expected argument type 'X'
body: <p>Xcode 8 and Swift 3 made me really sad today :(</p>
  
  <p>Please have a look and tell me if you ever had something like this and if it's possible to fix it. I've been trying different solutions, among them:</p>
  
  <ol>
  <li>Cmd + Shift + K</li>
  <li>Cmd + Shift + Option + K</li>
  <li>Delete Derived Data</li>
  <li>Change used struct (it's a nested struct in my code), flattened it, change to really basic one</li>
  </ol>
  
  <p><a href="https://i.stack.imgur.com/ZpfWv.png" rel="noreferrer"><img src="https://i.stack.imgur.com/ZpfWv.png" alt="Sad Xcode error"></a></p>
  
  <p><strong>Update 1:</strong></p>
  
  <p>Here's the code (although I think it's not necessarily a problem related to my implementation), it's in my tests target:</p>
  
  <pre><code>let viewModelStub: Quiz.NewRoundDetails.ViewModel = Quiz.NewRoundDetails.ViewModel(roundNumber: "", score: "", proposedAnswerParts: [
              Quiz.NewRoundDetails.ViewModel.AnswersForComponent(answers: []),
              Quiz.NewRoundDetails.ViewModel.AnswersForComponent(answers: []),
              Quiz.NewRoundDetails.ViewModel.AnswersForComponent(answers: [])])
  
  _ = viewController.view
  viewController.display(roundModel: viewModelStub)
  </code></pre>
  
  <p>Here are structs:</p>
  
  <pre><code>struct Quiz {
      struct NewRoundDetails {
          struct Response {
              let roundNumber: Int
              let score: Int
          }
          struct ViewModel {
              let roundNumber: String
              let score: String
              let proposedAnswerParts: [Quiz.NewRoundDetails.ViewModel.AnswersForComponent]
  
              struct AnswersForComponent {
                  let answers: [String]
              }
          }
      }
  }
  </code></pre>
  
  <p>And in viewController things look like this:</p>
  
  <pre><code>func display(roundModel: Quiz.NewRoundDetails.ViewModel) {
      ...
  }
  </code></pre>
  
  <p>Nothing so unusual I think. I have just discovered one more thing - the code works fine on the app target side, it doesn't work on tests target.</p>
  
  <p>I don't have more ideas atm... Can you help me? I have created radar as well</p>