Foogen

foo.scala

package mydsltry2

import shapeless._
import shapeless.{ HList, ::, HNil }
import scala.language.implicitConversions

trait UTupler[A] {
  type Out
}

object UTupler extends LowPriority {
  
  trait Auxilary[A,B,R] { //A::B::R
    type Out
  }
  
  trait Auxilary2[A,B,R, R1] { //A::B::R
    type Out
  }
  
  trait Aux[A,R] {
    type Out
  }
  
  implicit def base0Utuple[A, R <: HList](t:(A,Unit), r:R)
    (implicit aux: Aux[A,R]): aux.Out = ???
    
  implicit def base1Utuple[A, R <: HList](t:(Unit, A), r:R)
    (implicit aux: Aux[A,R]): aux.Out = ???
    
  implicit def utuple[A,B, R <: HList](t: (A,B), r: R)
    (implicit auxilary: Auxilary[A,B,R]): auxilary.Out = ???
    
  // now two way merge
  implicit def auxilary[A,B,R1 <: HList, R2 <: HList](a:A, b:B, r:R1)
     (implicit auxA:Aux[A,R2], auxB: Aux[B,R1]) : Auxilary2[A,B,R1, auxB.Out] = 
       new Auxilary2[A,B,R1,auxB.Out] {
         type Out = auxA.Out
       }
}

trait LowPriority {
  
  implicit def anyToUTuple[A, R <: HList](a:A, r:R) : A :: R = ??? // aha, yeah
}


object MyDsl {
  
  def convert[A](a:A)(implicit utupler: UTupler[A]): utupler.Out = ???
  
}