如何为非密封Trait的Coproduct自动推导Shapeless LabelledGeneric

我尝试为Coproduct生成LabelledGeneric，以此替代常规的sealed trait继承体系。目前已通过显式指定DefaultSymbolicLabelling的标签实现该功能，但认为应可直接从Coproduct的类型成员自动推导，无需手动定义标签及相关实例。

手动实现代码示例 #

/**
 * So far I found no way to derive `L` and `l` from `C`.
 */
object ShapelessLabelledGenericForCoproduct extends App {
  trait Base // not sealed!

  case class Case1(a: Int) extends Base

  case class Case2(a: String) extends Base

  case class Case3(b: Boolean) extends Base

  object Base {
    type C = Case1 :+: Case2 :+: Case3 :+: CNil

    type L = (Symbol @@ "Case1") :: (Symbol @@ "Case2") :: (Symbol @@ "Case3") :: shapeless.HNil
    val l: L = tag["Case1"](Symbol("Case1")) :: tag["Case2"](Symbol("Case2")) :: tag["Case3"](Symbol("Case3")) :: HNil

    implicit def myGeneric: Generic.Aux[Base, C] = Generic.instance[Base, C](
      v => Coproduct.runtimeInject[C](v).get,
      v => Coproduct.unsafeGet(v).asInstanceOf[Base]
    )

    implicit def mySymbolicLabelling: DefaultSymbolicLabelling.Aux[Base, L] = DefaultSymbolicLabelling.instance[Base, L](l)
  }

  val lgen = LabelledGeneric[Base]
  val repr = lgen.to(Case1(123))
  println(lgen.from(repr))
}

密封Trait自动推导的参考代码（期望非密封Trait实现类似效果） #

object ShapelessLabelledGenericForSealedTrait extends App {
  sealed trait Base

  case class Case1(a: Int) extends Base

  case class Case2(a: String) extends Base

  case class Case3(b: Boolean) extends Base

  val lgen = LabelledGeneric[Base]
  val repr = lgen.to(Case1(123))
  println(lgen.from(repr))
}

我已查阅Shapeless宏代码，但未找到有用线索，求相关实现思路？

内容的提问来源于stack exchange，提问作者user3663733