CirceGenericWithDerivation.scala

import io.circe.Encoder
import shapeless.Unwrapped
import io.circe.derivation
import io.circe.syntax._

object Main extends App {

  case class FooId(value: String) extends AnyVal

  case class Foo(id: FooId, bar: String)

  implicit def anyValEncoder[V, U](implicit ev: V <:< AnyVal,
                                   V: Unwrapped.Aux[V, U],
                                   encoder: Encoder[U]): Encoder[V] =
    encoder.contramap(V.unwrap)

  // produce `Error:scalac: Error while emitting Main.scala key not found: value inst$macro$8` if line below is commented
  // implicit val idEncoder = Encoder.instance[FooId](_.value.asJson)

  implicit val fooEncoder = derivation.deriveEncoder[Foo]

  println(Foo(FooId("abc"), "cba").asJson.noSpaces)

}