how to modularize scala code properly?

demo.scala

trait FooComponent {
  def fooService: FooService

  trait FooService {
    def query: String
  }
}

trait ConcreteFooComponent extends FooComponent {
  val fooService = ???
}

trait QueryRoutes {
  this: FooComponent =>
  val queryRoute = get {
    complete(fooService.query)
  }
}

trait OtherRoutes {
  val otherRoute = ???
}

trait HttpService extends QueryRoutes with OtherRouters {        // 编译不过，因为QueryRoutes声明了self type annotation
  val route = queryRoute ~ otherRoute
}

object Main extends HttpService with ConcreteFooComponent with App {

}

trait HttpService extends QueryRoutes with OtherRouters {
this: FooComponent =>
val route = queryRoute ~ otherRoute
}

trait HttpService extends QueryRoutes with OtherRouters {
//加上
this: FooComponent =>
val route = queryRoute ~ otherRoute
}