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你能解释一下副产品是如何工作的吗？这是我的代码

sealed trait ArdbData

case class ArdbDataString(value: String) extends ArdbData

case class ArdbDataLong(value: Long) extends ArdbData

case class ArdbDataDouble(value: Double) extends ArdbData

object ArdbDataString {
  implicit val codec: Codec[ArdbDataString] = // ... some codec here
  implicit val discriminator: Discriminator[ArdbData, ArdbDataString, Int] = Discriminator(6)
}

object ArdbDataLong {

  implicit val codec: Codec[ArdbDataLong] = // ... some codec here
  implicit val discriminator: Discriminator[ArdbData, ArdbDataLong, Int] = Discriminator(1)
}

object ArdbDataDouble {
  implicit val codec: Codec[ArdbDataDouble] = // ... some codec here
  implicit val discriminator: Discriminator[ArdbData, ArdbDataDouble, Int] = Discriminator(2)
}

object ArdbData {
  implicit val discriminated: Discriminated[ArdbData, Int] = Discriminated(uint8)

  import shapeless.syntax.singleton._

//  implicit val codec: Codec[ArdbData] = Codec.coproduct[ArdbData].discriminatedBy(uint8).using(
//    'ArdbDataString ->> 4 :: 'ArdbDataLong ->> 1 :: 'ArdbDataDouble ->> 2 :: HNil)
}

我想我必须定义 coproduct 编解码器，ArdbData如本测试所示。我还需要为我在discriminatedBy.using(). 当我开始测试它时，我突然发现.using没有使用来自的密钥。而是使用每个Discriminator实例的 ID。然后我注释掉Codec.coproduct[ArdbData]它仍然可以编译！为什么会编译？定义鉴别器价值的正确方法是什么？

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