heksesang

object hlists
  enum HList
    case :*:[+H, +T <: HList](head: H, tail: T)
    case HNil

    def :*:[H](h: H): H :*: this.type = new HList.:*:(h, this)
    
    override def toString: String = this match
      case HList.:*:(head, tail) => s"($head) :: $tail"
      case HList.HNil => "HNil"

heksesang

import shapeless._
import shapeless.labelled._
import syntax.singleton._

sealed trait Event[A] {
  def replay(initial: Option[A]): Option[A]
}

case class NameChangedEvent[A: NameChangedEvent.Update](name: String) extends Event[A] {
  def replay(initial: Option[A]): Option[A] =