Explicit type for a Shapeless record, version: type FieldType[K, V] = (K, V)

gistfile1.scala

// See https://gist.github.com/jonifreeman/6533463
object TestExplicitRecordType {
 import shapeless._, record._, syntax.singleton._

  object testF extends Poly1 {
    implicit def atFieldType[K, V] = at[(K, V)] {
      case (k, v) => k.toString
    }
  }
 
  // Is there more straighforward way to give an explicit type for a record?
  val k1 = Witness("k1")
  val k2 = Witness("k2")
  type Error = (k1.T, String) :: (k2.T, Long) :: HNil
 
  // That seems to work...
  val err1        = "k1" ->> "1" :: "k2" ->> 1L :: HNil
  val err2: Error = "k1" ->> "1" :: "k2" ->> 1L :: HNil
 
  // ... and getting the key works too since no need for Witness.Aux
  testF(err1.head) // OK
  testF(err2.head) // OK
}