shapeless implicit LeftFolder resolution

TestTypify.scala

import $ivy.`com.chuusai::shapeless:2.3.3`
// import $ivy.`com.chuusai::shapeless:2.3.4-SNAPSHOT`

import $ivy.`org.scalaz::scalaz-core:7.2.17`

interp.repositories() ++= Seq(coursier.MavenRepository("https://dl.bintray.com/bondlink/Typify"))
import $ivy.`typify::typify:2.4.1`

import shapeless.{::, HNil}
import shapeless.syntax.singleton._
import typify.{Typify, Parsed, ParseError}
import typify.convert._
import typify.convert.syntax._
import typify.parsedany._
import scalaz.NonEmptyList
import scalaz.syntax.either._
import scalaz.syntax.nel._
import scalaz.syntax.validation._

case class Fail(reason: String)

val tp = new Typify[Fail, Parsed[Any]]

implicit val parse2Error = (p: Parsed[Any], pe: ParseError) => Fail(s"${pe.key} - ${pe.error}")

val checkEmail = Typify.validate((s: String) =>
  s.right[NonEmptyList[Fail]]
   .ensure(Fail("Email is invalid").wrapNel)(_.contains("@"))
   .validation)

val checkAge = Typify.validate((i: Int) =>
  i.right[NonEmptyList[Fail]]
   .ensure(Fail("Too young").wrapNel)(_ > 21)
   .validation)

val checkSessId = Typify.optional((i: Int) =>
  i.right[NonEmptyList[Fail]]
   .ensure(Fail("Invalid session id").wrapNel)(_ > 3000)
   .validation)

val checkPerson = 'email ->> checkEmail :: 'age ->> checkAge :: 'session ->> checkSessId :: HNil

import tp.syntax._

val passes: Any = Map("email" -> "foo@bar", "age" -> 22, "session" -> 77777, 3 -> "junk")

// Fails on 2.3.3 but passes with #686 reverted
val passed = Parsed(passes).parse(checkPerson)