Shapeless tuple flatten

flatten.scala

import shapeless._
import poly._
import shapeless.ops.tuple.FlatMapper
import syntax.std.tuple._

object Flatten {
  trait LowPriorityFlatten extends Poly1 {
    implicit def default[T] = at[T](Tuple1(_))
  }
  object flatten extends LowPriorityFlatten {
    implicit def caseTuple[P <: Product](implicit fm: FlatMapper[P, flatten.type]) =
      at[P](_.flatMap(flatten))
  }

  def main(args: Array[String]) {
    println(flatten((1, (2, (3, (4, 5))))).toList)
  }
}