scala - 是否可以使用适用于 Everywhere 的非对象 shapeless.Poly1？

Question

我的以下尝试不起作用:

class Absolute(rootDir: File) extends Poly1 {
  implicit def caseFile[F <: File]: Case[F] { type Result = File } = at[F] { f =>
    if (f.isAbsolute)
      f
    else
      val parts =
        file.getPath.split(Pattern.quote(File.separator)).toList.filterNot(Set("", "."))
      parts match {
        case ":root-dir" :: tail => tail.foldLeft(rootDir)(new File(_, _))
        case ":home" :: tail => tail.foldLeft(new File(sys.props("user.home")))(new File(_, _))
        case _ => f
      }
  }
}

object Absolutised {
  def from(rootDir: File) = new Runner(new Absolute(rootDir))

  final class Runner(absolute: Absolute) {
    def apply[T](t: T)(implicit everywhere: Everywhere[absolute.type, T]) = everywhere(t)
  }
}

Answer 1

不理想，但在 scala 2.11.8 和 shapeless 2.3.0 中有一个解决方法:

object Absolutised {
  def from(rootDir: File) = new Runner(rootDir)

  final class Runner(rootDir: File) {

    object ab2 extends Absolute(rootDir)

    def apply[T](t: T)(implicit everywhere: Everywhere[ab2.type, T]) = everywhere(t)
  }
}