kp-errors.scala

  trait X[A <: AnyKind, F[_ <: AnyKind]] { type B = F[A] }

  // OK
  val i5: X[Option, ({ type l[X[_]] = X[Int] })#l]#B = Some(5)

  /////////////////////////////////////////////////////////////
  // KO
  val i1: X[Option, List]#B = Some(5)  
  
  // Error Before Patch
  kind-poly14.scala:45: error: type mismatch;
  found   : Some[Int]
  required: List[Option]
    val i: X[Option, List]#B = Some(5)                         ^
  // Now
  kind-poly14.scala:45: error: [Kind-Polymorphic Error] X[Option, List]#B inferred to type List[Option] with illegal kind type argument Option applied to type List[A]
    val i: X[Option, List]#B = Some(5)  
                           ^
  /////////////////////////////////////////////////////////////
  val j: X[Double, ({ type l[X[_]] = X[Int] })#l]#B = 5.0

  // Before Patch
  error: null
  // Now
  kind-poly14.scala:51: error: [Kind-Polymorphic Error] X[Double, scala.AnyRef {
    type l[X[_] >: [_]Nothing <: [_]Any] = X[Int]
  }#l]#B inferred to type Double[Int] with illegal kind type argument Int applied to type Double
    val j: X[Double, ({ type l[X[_]] = X[Int] })#l]#B = 5.0
                                                    ^                           
  /////////////////////////////////////////////////////////////
  // KO
  val i0: X[Option, Double]#B = Some(5)  

  // Error
  kind-poly14.scala:48: error: Double takes no type parameters, expected: one
    val i0: X[Option, Double]#B = Some(5)
                      ^
  /////////////////////////////////////////////////////////////
  // KO
  val i1: X[Option, List]#B = Some(5)  
  // Error
  kind-poly14.scala:51: error: [Kind-Polymorphic Error] X[Option, List]#B inferred to type List[Option] with illegally kinded type arguments Option applied to type List[A]
    val i1: X[Option, List]#B = Some(5)
                            ^
  /////////////////////////////////////////////////////////////
  // KO
  val i3: X[Option[Double], ({ type l[X[_]] = X[Int] })#l]#B = Some(5)
  // Error
  kind-poly14.scala:54: error: type mismatch;
   found   : Some[Int]
   required: List[Option[Double]]
    val i2: X[Option[Double], List]#B = Some(5)
                                            ^
  /////////////////////////////////////////////////////////////
  // KO
  val i4: X[Double, ({ type l[X[_]] = X[Int] })#l]#B = 5.0
  // ERROR
  kind-poly14.scala:60: error: [Kind-Polymorphic Error] X[Double, scala.AnyRef {
    type l[X[_] >: [_]Nothing <: [_]Any] = X[Int]
  }#l]#B inferred to type Double[Int] with illegally kinded type arguments Int applied to type Double
    val i4: X[Double, ({ type l[X[_]] = X[Int] })#l]#B = 5.0
                                                     ^
  /////////////////////////////////////////////////////////////
  // KO
  val i6: X[Either, ({ type l[X[_]] = X[Int] })#l]#B = Some(5)
  // ERROR
  kind-poly14.scala:66: error: [Kind-Polymorphism Error] Invalid inferred kind-polymorphic type Either[Int]
  trying to apply bad number(1) of arguments [Int] to type Either[A,B]
    val i6: X[Either, ({ type l[X[_]] = X[Int] })#l]#B = Some(5)
                                                     ^
  /////////////////////////////////////////////////////////////
  // KO
  val i7: X[Either, List]#B = Some(5)
  // ERROR
  kind-poly14.scala:69: error: [Kind-Polymorphic Error] X[Either, List]#B inferred to type List[[+A, +B]scala.util.Either[A,B]]
  with illegally kinded type arguments [+A, +B]scala.util.Either[A,B] applied to type List[A]
    val i7: X[Either, List]#B = Some(5)
                            ^