https://medium.com/@maximilianofelice/builder-pattern-in-scala-with-phantom-types-3e29a167e863

Pizza.scala

object Main extends App {
  case class Food(ingredients: Seq[String])

  class Chef[Pizza <: Chef.Pizza](ingredients: Seq[String] = Seq()) {
    import Chef.Pizza._

    def addCheese(cheeseType: String): Chef[Pizza with Cheese] = new Chef(ingredients :+ cheeseType)

    def addTopping(toppingType: String): Chef[Pizza with Topping] = new Chef(ingredients :+ toppingType)

    def addDough: Chef[Pizza with Dough] = new Chef(ingredients :+ "dough")

    def build(implicit ev: Pizza =:= FullPizza): Food = Food(ingredients)
  }

  object Chef {
    def newChef = new Chef[Pizza.EmptyPizza]()

    sealed trait Pizza
    object Pizza {
      sealed trait EmptyPizza extends Pizza
      sealed trait Cheese extends Pizza
      sealed trait Topping extends Pizza
      sealed trait Dough extends Pizza

      type FullPizza = EmptyPizza with Cheese with Topping with Dough
    }
  }

  val c =
    Chef.newChef
      .addCheese("mozzarella")
      .addDough

  val p =
    c.addTopping("olives")
      .build

  println(p)
}