Can't infer PBWriter for recursive Coproducts

[vovapolu]

For example I want infer pbdirect instances for the following sealed trait:

import pbdirect._

sealed trait MyList

case class Cons(i: Int, l: MyList) extends MyList
case object Nil extends MyList

PBWriter[MyList] // error: could not find implicit value for evidence parameter of type pbdirect.PBWriter[MyList]
PBReader[MyList] // ok

PBReader is inferred just fine, but PBWriter is not.

My guess is that it should be tail: Lazy[PBWriter[T]] in implicit def cconsWriter instead of just tail: PBWriter[T]

implicit def cconsWriter[H, T <: Coproduct](
      implicit head: PBWriter[H],
      tail: PBWriter[T]): PBWriter[H :+: T] // it should be Lazy[PBWriter[T]]

just as it's implemented for PBReader

implicit def cconsParser[H, T <: Coproduct](
      implicit
      head: PBParser[H],
      tail: Lazy[PBParser[T]]): PBParser[H :+: T]