Code for path-dependent type post.

gistfile1.scala

trait InfoNeed {
  type DataType
  /** Get the web request to fetch data */
  def request: WebRequest[DataType]
  /** Get the neighbors from some fetched data (to determine new nodes to visit) */
  def neighbors(data: DataType): Traversable[Node]
  /** Save the data to the data store. */
  def save(store: DataStore, data: DataType)
}

gistfile2.scala

def fetch[T](req: WebRequest[T]): Result[T]

def process(need: Need) {
  val req = need.request
  val res = fetch(req)
  // now we save the data
  res match {
    case Good(data) => need.save(store, data)
    /* error cases */
  }
}