hmap.scala

package m

import shapeless.HMap


object leData {
  object Name
  object Age
  object Address
  object Street
  object City
  object State

  class Direction[K, V]
  class Person[K, V]
  implicit val personNameAsString       = new Person[Name.type    , String]
  implicit val personAgeAsInt           = new Person[Age.type     , Int]
  implicit val personAddressAsDirection = new Person[Address.type , HMap[Direction]]

  implicit val directionStreetAsString  = new Direction[Street.type , String]
  implicit val directionCityAsString    = new Direction[City.type   , String]
  implicit val directionStateAsString   = new Direction[State.type  , String]
}

object EnrichedTrav {
  // Enrich HMap to provide \ operator for types HMap and Option[HMap]
  implicit class Navi[R[_, _]](h: HMap[R]) {
    def \[K, V](k: K)(implicit ev : R[K, V]) : Option[V] = h.get(k)
  }
  implicit class NaviOpt[R[_, _]](h: Option[HMap[R]]) {
    def \[K, V](k: K)(implicit ev : R[K, V]) : Option[V] = h.flatMap(_.get(k))
  }
}

object Main extends App {


  import EnrichedTrav._
  import leData._ // you do need to import the type map 
  val hm = HMap[Person].apply(
    Name -> "Tim",
    Age -> 33,
    Address -> HMap[Direction](
      Street -> "Very Street",
      City -> "SL",
      State -> "UT"))

  // Compiler knows result is Option[Int]
  val age = hm \ Age

  // Compiler knows result is Option[String]
  val address = hm \ Address \ City

  // Doesn't compile; Compiler knows that Name can not be a member of HMap[Direction]
  val addressName = hm \ Address \ Name
}