tlist.scala

sealed trait TList[X, Z]
case class TCons[X, Y, Z](head: X => Y, tail: TList[Y,Z]) extends TList[X, Z]
case class TEnd[X,Z](f: X => Z) extends TList[X, Z]

object Evaluators {
  def safe1[X,Z](x: X, tList: TList[X, Z]): Z = tList match {
    case TCons(head, tail) => safe1(head(x), tail)
    case TEnd(f) => f(x)
  }
  // dotty: Warning
  // scala: Fine

  def unsafe1[X,Z](x: X, tList: TList[X, Z]): Z = tList match {
    case TCons(head, tail) => safe1("WTF", tail)
    case TEnd(f) => f(x)
  }
  // dotty: Warning
  // scala: Fine

  def safe2[X,Z](x: X, tList: TList[X, Z]): Z = tList match {
    case tCons: TCons[X, _, Z] => safe2(tCons.head(x), tCons.tail)
    case TEnd(f) => f(x)
  }
  // dotty: Error
  // scala: Fine

  def unsafe2[X,Z](x: X, tList: TList[X, Z]): Z = tList match {
    case tCons: TCons[X, _, Z] => unsafe2("WTF", tCons.tail)
    case TEnd(f) => f(x)
  }
  // dotty: Error
  // scala: Error

  def safe3[X,Y,Z](x: X, tList: TList[X, Z]): Z = tList match {
    case tCons: TCons[X, Y, Z] => safe3(tCons.head(x), tCons.tail)
    case TEnd(f) => f(x)
  }
  // dotty: Fine
  // scala: Warning (Erasure)

  def unsafe3[X,Y,Z](x: X, tList: TList[X, Z]): Z = tList match {
    case tCons: TCons[X, Y, Z] => unsafe3("WTF", tCons.tail)
    case TEnd(f) => f(x)
  }
  // dotty: Error
  // scala: Error
}

sealed trait TList[X, Z]
case class TCons[X, Y, Z](head: X => Y, tail: TList[Y,Z]) extends TList[X, Z]
case class TEnd[X,Z](f: X => Z) extends TList[X, Z]

object Evaluators {
  def safe1[X,Z](x: X, tList: TList[X, Z]): Z = tList match {
    case TCons(head, tail) => safe1(head(x), tail)
    case TEnd(f) => f(x)
  }
  // dotty 0.5   : Warning
  // scala 2.11.8: Fine
  // scala 2.12.4: Fine

  def unsafe1[X,Z](x: X, tList: TList[X, Z]): Z = tList match {
    case TCons(head, tail) => safe1("WTF", tail)
    case TEnd(f) => f(x)
  }
  // dotty 0.5   : Warning
  // scala 2.11.8: Fine
  // scala 2.12.4: Fine

  def safe2[X,Z](x: X, tList: TList[X, Z]): Z = tList match {
    case tCons: TCons[X, _, Z] => safe2(tCons.head(x), tCons.tail)
    case TEnd(f) => f(x)
  }
  // dotty 0.5   : Error
  // scala 2.11.8: Fine
  // scala 2.12.4: Fine

  def unsafe2[X,Z](x: X, tList: TList[X, Z]): Z = tList match {
    case tCons: TCons[X, _, Z] => unsafe2("WTF", tCons.tail)
    case TEnd(f) => f(x)
  }
  // dotty 0.5   : Error
  // scala 2.11.8: Error
  // scala 2.12.4: Error

  def safe3[X,Y,Z](x: X, tList: TList[X, Z]): Z = tList match {
    case tCons: TCons[X, Y, Z] => safe3(tCons.head(x), tCons.tail)
    case TEnd(f) => f(x)
  }
  // dotty 0.5   : Fine
  // scala 2.11.8: Warning (Erasure)
  // scala 2.12.4: Warning (Erasure)

  def unsafe3[X,Y,Z](x: X, tList: TList[X, Z]): Z = tList match {
    case tCons: TCons[X, Y, Z] => unsafe3("WTF", tCons.tail)
    case TEnd(f) => f(x)
  }
  // dotty 0.5   : Error
  // scala 2.11.8: Error
  // scala 2.12.4: Error
}