gistfile1.txt

import io.circe.Encoder
import io.circe.syntax._

trait HasId[ID] {
  def id: ID
}

case class MyEntity(field1: Int, id: String) extends HasId[String]

case class CustomId(field1:Int)

object CustomId {

  implicit val myid:MyId[CustomId,Int] = _.field1
}

trait MyId[-E,Id]{
  def apply(v:E):Id
}

object MyId {
  implicit def myId_hasId_compat[E <: HasId[T], T]:MyId[HasId[T],T] = (v: HasId[T]) => v.id
}

def kokoko[Entity,T](entity: Entity)(implicit Id:MyId[Entity,T], enc: Encoder[T]): Unit = {
  println(Id(entity).asJson)
}


val inst = MyEntity(1, "kek")

kokoko(inst)
kokoko(CustomId(555))