Shapeless error: not found: value Second

Question

我正在关注一个包含以下代码的项目：

package ch.khinkali

import shapeless.{::, HList, HNil}


trait Second[L <: HList] {
  type Out

  def apply(value: L): Out
}

object Second {
  type Aux[L <: HList, O] = Second[L] {type Out = O}

  def apply[L <: HList](implicit inst: Second[L]): Aux[L, inst.Out] =
    inst
}


object Main {

  implicit def hlistSecond[A, B, Rest <: HList]: Second.Aux[A :: B :: Rest, B] =
    new Second[A :: B :: Rest] {
      type Out = B

      def apply(value: A :: B :: Rest): B =
        value.tail.head
    }

  def main(args: Array[String]): Unit = {

    val second1 = Second[String :: Boolean :: Int :: HNil]
    println(second1)
  }

}

当我尝试以下 Shell 时：

 val second1 = Second[String :: Boolean :: Int :: HNil]

显示错误信息：

 error: not found: value Second

我导入了包，如下图所示：

我做错了什么？

Answer 1

尝试通配符导入：

import ch.khinkali._
import shapeless._
import ch.khinkali.Main._

Shapeless error: not found: value Second

Shapeless error: not found: value Second

scala

shapeless