title: Spray route inside IDEA complains about false error
body: <p>I'm using spray and I have the following code:</p>
  
  <pre><code>import spray.json.DefaultJsonProtocol
  import spray.routing.Directives
  import spray.httpx.SprayJsonSupport.sprayJsonMarshaller
  import spray.httpx.SprayJsonSupport.sprayJsonUnmarshaller
  
  case class SomeResult(id: String, color: String)
  
  trait Protocols extends DefaultJsonProtocol {
    implicit val someResultFormat = jsonFormat2(SomeResult)
  }
  
  trait Api extends Directives with Protocols {
  
    val route =
      path("order" / IntNumber) { id =&gt;
        get {
          complete {
            val result: List[SomeResult] = List(SomeResult("foo", "green"+id), SomeResult("bar", "red"+id))
            result
          } // ERROR HERE
        }
      }
  }
  </code></pre>
  
  <p>This compiles and runs fine, however, inside IntelliJ IDEA editor it complains about an error. Namely, it says that <em>Expression of type List[SomeResult] doesn't conform to expected type ToResponseMarshallable</em>. How can I avoid the IDE complaining about such things? is there any fix for this? is it a well-known error? I already invalidated cache files and restarted but the error persist.</p>
  
  <p>FWIW, I'm using:</p>
  
  <p>Scala 2.11.1</p>
  
  <p>Spray 1.3.1</p>
  
  <p>IDEA  14.0.3</p>
  
  <p>Scala plugin 1.3.2</p>
  
  <p>JDK   1.7.0_71</p>