match type, poly function: orphan parameter reference

[Jasper-M]

minimized code

scala> type Bar[X] = X match { 
     |   case List[a] => List[Tuple1[a]]
     |   case Set[a] => Set[Tuple1[a]]
     | }

scala> (Set(1,2,3), List("a","b")).map([A] => (a: A) => a match {
     |   case it: Iterable[x] => it.map(Tuple1(_)).asInstanceOf[Bar[A]]
     | })

Crash output (click arrow to expand)

error when pickling type a
error when pickling type Set[a]
error when pickling type (Set[a], List[String])
error when pickling tree (Set[a], List[String])
error when pickling tree val Tuple_this: (Set[a], List[String]) = 
  Tuple2.apply[Set[a], List[String]](Set.apply[a]([1,2,3 : a]:a*), 
    List.apply[String](["a","b" : String]:String*)
  )
error when pickling tree {
  val f: PolyFunction{apply: [A](a: A): Bar[A]} = 
    {
      final class $anon() extends Object(), PolyFunction {
        def apply[A >: Nothing <: Any](a: A): Bar[A] = 
          a match 
            {
              case it @ _:Iterable[x @ _] => 
                it.map[Tuple1[x]](
                  {
                    def $anonfun(_$2: x): Tuple1[x] = Tuple1.apply[x](_$2)
                    closure($anonfun)
                  }
                ).asInstanceOf[Bar[A]]
            }
      }
      new $anon():PolyFunction{apply: [A](a: A): Bar[A]}
    }
  val Tuple_this: (Set[a], List[String]) = 
    Tuple2.apply[Set[a], List[String]](Set.apply[a]([1,2,3 : a]:a*), 
      List.apply[String](["a","b" : String]:String*)
    )
  runtime.DynamicTuple.dynamicMap[(Tuple_this : (Set[a], List[String])), Bar](
    {
      Tuple_this
    }
  , 
    {
      f
    }
  ):
    Tuple.Map[
      {
        Tuple_this
      }.type
    , Bar]
}
error when pickling tree val res4: (Set[Tuple1[Int]], List[Tuple1[String]]) = 
  {
    val f: PolyFunction{apply: [A](a: A): Bar[A]} = 
      {
        final class $anon() extends Object(), PolyFunction {
          def apply[A >: Nothing <: Any](a: A): Bar[A] = 
            a match 
              {
                case it @ _:Iterable[x @ _] => 
                  it.map[Tuple1[x]](
                    {
                      def $anonfun(_$2: x): Tuple1[x] = Tuple1.apply[x](_$2)
                      closure($anonfun)
                    }
                  ).asInstanceOf[Bar[A]]
              }
        }
        new $anon():PolyFunction{apply: [A](a: A): Bar[A]}
      }
    val Tuple_this: (Set[a], List[String]) = 
      Tuple2.apply[Set[a], List[String]](Set.apply[a]([1,2,3 : a]:a*), 
        List.apply[String](["a","b" : String]:String*)
      )
    runtime.DynamicTuple.dynamicMap[(Tuple_this : (Set[a], List[String])), Bar](
      {
        Tuple_this
      }
    , 
      {
        f
      }
    ):
      Tuple.Map[
        {
          Tuple_this
        }.type
      , Bar]
  }
error when pickling tree () extends Object(), _root_.scala.Serializable { this: rs$line$9.type =>
  private def writeReplace(): AnyRef = 
    new scala.runtime.ModuleSerializationProxy(classOf[rs$line$9.type])
  val res4: (Set[Tuple1[Int]], List[Tuple1[String]]) = 
    {
      val f: PolyFunction{apply: [A](a: A): Bar[A]} = 
        {
          final class $anon() extends Object(), PolyFunction {
            def apply[A >: Nothing <: Any](a: A): Bar[A] = 
              a match 
                {
                  case it @ _:Iterable[x @ _] => 
                    it.map[Tuple1[x]](
                      {
                        def $anonfun(_$2: x): Tuple1[x] = Tuple1.apply[x](_$2)
                        closure($anonfun)
                      }
                    ).asInstanceOf[Bar[A]]
                }
          }
          new $anon():PolyFunction{apply: [A](a: A): Bar[A]}
        }
      val Tuple_this: (Set[a], List[String]) = 
        Tuple2.apply[Set[a], List[String]](Set.apply[a]([1,2,3 : a]:a*), 
          List.apply[String](["a","b" : String]:String*)
        )
      runtime.DynamicTuple.dynamicMap[(Tuple_this : (Set[a], List[String])), Bar
        ]
      (
        {
          Tuple_this
        }
      , 
        {
          f
        }
      ):
        Tuple.Map[
          {
            Tuple_this
          }.type
        , Bar]
    }
}
error when pickling tree @scala.annotation.internal.SourceFile("rs$line$9") final module class rs$line$9$
  (
) extends Object(), _root_.scala.Serializable { this: rs$line$9.type =>
  private def writeReplace(): AnyRef = 
    new scala.runtime.ModuleSerializationProxy(classOf[rs$line$9.type])
  val res4: (Set[Tuple1[Int]], List[Tuple1[String]]) = 
    {
      val f: PolyFunction{apply: [A](a: A): Bar[A]} = 
        {
          final class $anon() extends Object(), PolyFunction {
            def apply[A >: Nothing <: Any](a: A): Bar[A] = 
              a match 
                {
                  case it @ _:Iterable[x @ _] => 
                    it.map[Tuple1[x]](
                      {
                        def $anonfun(_$2: x): Tuple1[x] = Tuple1.apply[x](_$2)
                        closure($anonfun)
                      }
                    ).asInstanceOf[Bar[A]]
                }
          }
          new $anon():PolyFunction{apply: [A](a: A): Bar[A]}
        }
      val Tuple_this: (Set[a], List[String]) = 
        Tuple2.apply[Set[a], List[String]](Set.apply[a]([1,2,3 : a]:a*), 
          List.apply[String](["a","b" : String]:String*)
        )
      runtime.DynamicTuple.dynamicMap[(Tuple_this : (Set[a], List[String])), Bar
        ]
      (
        {
          Tuple_this
        }
      , 
        {
          f
        }
      ):
        Tuple.Map[
          {
            Tuple_this
          }.type
        , Bar]
    }
}
error when pickling tree package <empty> {
  final lazy module val rs$line$9: rs$line$9$ = new rs$line$9$()
  @scala.annotation.internal.SourceFile("rs$line$9") final module class 
    rs$line$9$
  () extends Object(), _root_.scala.Serializable { this: rs$line$9.type =>
    private def writeReplace(): AnyRef = 
      new scala.runtime.ModuleSerializationProxy(classOf[rs$line$9.type])
    val res4: (Set[Tuple1[Int]], List[Tuple1[String]]) = 
      {
        val f: PolyFunction{apply: [A](a: A): Bar[A]} = 
          {
            final class $anon() extends Object(), PolyFunction {
              def apply[A >: Nothing <: Any](a: A): Bar[A] = 
                a match 
                  {
                    case it @ _:Iterable[x @ _] => 
                      it.map[Tuple1[x]](
                        {
                          def $anonfun(_$2: x): Tuple1[x] = Tuple1.apply[x](_$2)
                          closure($anonfun)
                        }
                      ).asInstanceOf[Bar[A]]
                  }
            }
            new $anon():PolyFunction{apply: [A](a: A): Bar[A]}
          }
        val Tuple_this: (Set[a], List[String]) = 
          Tuple2.apply[Set[a], List[String]](Set.apply[a]([1,2,3 : a]:a*), 
            List.apply[String](["a","b" : String]:String*)
          )
        runtime.DynamicTuple.dynamicMap[(Tuple_this : (Set[a], List[String])), 
          Bar
        ](
          {
            Tuple_this
          }
        , 
          {
            f
          }
        ):
          Tuple.Map[
            {
              Tuple_this
            }.type
          , Bar]
      }
  }
}
Exception in thread "main" java.lang.AssertionError: assertion failed: orphan parameter reference: TypeParamRef(a)
	at dotty.DottyPredef$.assertFail(DottyPredef.scala:17)
	at dotty.tools.dotc.core.tasty.TreePickler.pickleNewType(TreePickler.scala:279)
	at dotty.tools.dotc.core.tasty.TreePickler.pickleType(TreePickler.scala:152)
	at dotty.tools.dotc.core.tasty.TreePickler.pickleNewType$$anonfun$11$$anonfun$1(TreePickler.scala:169)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:15)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:10)
	at scala.collection.immutable.List.foreach(List.scala:305)
	at dotty.tools.dotc.core.tasty.TreePickler.pickleNewType$$anonfun$1(TreePickler.scala:169)
	at dotty.runtime.function.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:12)
	at dotty.tools.dotc.core.tasty.TreePickler.withLength(TreePickler.scala:47)
	at dotty.tools.dotc.core.tasty.TreePickler.pickleNewType(TreePickler.scala:169)
	at dotty.tools.dotc.core.tasty.TreePickler.pickleType(TreePickler.scala:152)
	at dotty.tools.dotc.core.tasty.TreePickler.pickleNewType$$anonfun$11$$anonfun$1(TreePickler.scala:169)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:15)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:10)
	at scala.collection.immutable.List.foreach(List.scala:305)
	at dotty.tools.dotc.core.tasty.TreePickler.pickleNewType$$anonfun$1(TreePickler.scala:169)
	at dotty.runtime.function.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:12)
	at dotty.tools.dotc.core.tasty.TreePickler.withLength(TreePickler.scala:47)
	at dotty.tools.dotc.core.tasty.TreePickler.pickleNewType(TreePickler.scala:169)
	at dotty.tools.dotc.core.tasty.TreePickler.pickleType(TreePickler.scala:152)
	at dotty.tools.dotc.core.tasty.TreePickler.pickleTree(TreePickler.scala:558)
	at dotty.tools.dotc.core.tasty.TreePickler.pickleTpt(TreePickler.scala:305)
	at dotty.tools.dotc.core.tasty.TreePickler.pickleDef$$anonfun$2(TreePickler.scala:320)
	at dotty.runtime.function.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:12)
	at dotty.tools.dotc.core.tasty.TreePickler.withLength(TreePickler.scala:47)
	at dotty.tools.dotc.core.tasty.TreePickler.pickleDef(TreePickler.scala:324)
	at dotty.tools.dotc.core.tasty.TreePickler.pickleTree(TreePickler.scala:509)
	at dotty.tools.dotc.core.tasty.TreePickler.pickleTree$$anonfun$42$$anonfun$1(TreePickler.scala:485)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:15)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:10)
	at scala.collection.immutable.List.foreach(List.scala:305)
	at dotty.tools.dotc.core.tasty.TreePickler.pickleTree$$anonfun$18(TreePickler.scala:485)
	at dotty.runtime.function.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:12)
	at dotty.tools.dotc.core.tasty.TreePickler.withLength(TreePickler.scala:47)
	at dotty.tools.dotc.core.tasty.TreePickler.pickleTree(TreePickler.scala:487)
	at dotty.tools.dotc.core.tasty.TreePickler.pickleTreeUnlessEmpty(TreePickler.scala:308)
	at dotty.tools.dotc.core.tasty.TreePickler.pickleDef$$anonfun$2(TreePickler.scala:322)
	at dotty.runtime.function.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:12)
	at dotty.tools.dotc.core.tasty.TreePickler.withLength(TreePickler.scala:47)
	at dotty.tools.dotc.core.tasty.TreePickler.pickleDef(TreePickler.scala:324)
	at dotty.tools.dotc.core.tasty.TreePickler.pickleTree(TreePickler.scala:509)
	at dotty.tools.dotc.core.tasty.TreePickler.pickleStats$$anonfun$2(TreePickler.scala:343)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:15)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:10)
	at scala.collection.immutable.List.foreach(List.scala:305)
	at dotty.tools.dotc.core.tasty.TreePickler.pickleStats(TreePickler.scala:343)
	at dotty.tools.dotc.core.tasty.TreePickler.pickleTree$$anonfun$25(TreePickler.scala:546)
	at dotty.runtime.function.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:12)
	at dotty.tools.dotc.core.tasty.TreePickler.withLength(TreePickler.scala:47)
	at dotty.tools.dotc.core.tasty.TreePickler.pickleTree(TreePickler.scala:547)
	at dotty.tools.dotc.core.tasty.TreePickler.pickleDef$$anonfun$2(TreePickler.scala:319)
	at dotty.runtime.function.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:12)
	at dotty.tools.dotc.core.tasty.TreePickler.withLength(TreePickler.scala:47)
	at dotty.tools.dotc.core.tasty.TreePickler.pickleDef(TreePickler.scala:324)
	at dotty.tools.dotc.core.tasty.TreePickler.pickleTree(TreePickler.scala:522)
	at dotty.tools.dotc.core.tasty.TreePickler.pickleStats$$anonfun$2(TreePickler.scala:343)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:15)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:10)
	at scala.collection.immutable.List.foreach(List.scala:305)
	at dotty.tools.dotc.core.tasty.TreePickler.pickleStats(TreePickler.scala:343)
	at dotty.tools.dotc.core.tasty.TreePickler.pickleTree$$anonfun$27(TreePickler.scala:556)
	at dotty.runtime.function.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:12)
	at dotty.tools.dotc.core.tasty.TreePickler.withLength(TreePickler.scala:47)
	at dotty.tools.dotc.core.tasty.TreePickler.pickleTree(TreePickler.scala:556)
	at dotty.tools.dotc.core.tasty.TreePickler.pickle$$anonfun$1(TreePickler.scala:713)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:15)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:10)
	at scala.collection.immutable.List.foreach(List.scala:305)
	at dotty.tools.dotc.core.tasty.TreePickler.pickle(TreePickler.scala:713)
	at dotty.tools.dotc.transform.Pickler.run$$anonfun$10$$anonfun$8(Pickler.scala:63)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:15)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:10)
	at scala.collection.immutable.List.foreach(List.scala:305)
	at dotty.tools.dotc.transform.Pickler.run$$anonfun$2(Pickler.scala:87)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:15)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:10)
	at scala.collection.immutable.List.foreach(List.scala:305)
	at dotty.tools.dotc.transform.Pickler.run(Pickler.scala:87)
	at dotty.tools.dotc.core.Phases$Phase.runOn$$anonfun$1(Phases.scala:315)
	at scala.collection.immutable.List.map(List.scala:219)
	at dotty.tools.dotc.core.Phases$Phase.runOn(Phases.scala:316)
	at dotty.tools.dotc.transform.Pickler.runOn(Pickler.scala:91)
	at dotty.tools.dotc.Run.runPhases$4$$anonfun$4(Run.scala:167)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:15)
	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:10)
	at scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1323)
	at dotty.tools.dotc.Run.runPhases$5(Run.scala:177)
	at dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:185)
	at dotty.runtime.function.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:12)
	at dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:64)
	at dotty.tools.dotc.Run.compileUnits(Run.scala:192)
	at dotty.tools.dotc.Run.compileUnits(Run.scala:134)
	at dotty.tools.repl.ReplCompiler.runCompilationUnit(ReplCompiler.scala:156)
	at dotty.tools.repl.ReplCompiler.compile(ReplCompiler.scala:166)
	at dotty.tools.repl.ReplDriver.compile(ReplDriver.scala:229)
	at dotty.tools.repl.ReplDriver.interpret(ReplDriver.scala:193)
	at dotty.tools.repl.ReplDriver.loop$1(ReplDriver.scala:127)
	at dotty.tools.repl.ReplDriver.runUntilQuit$$anonfun$1(ReplDriver.scala:130)
	at dotty.tools.repl.ReplDriver.withRedirectedOutput(ReplDriver.scala:148)
	at dotty.tools.repl.ReplDriver.runUntilQuit(ReplDriver.scala:130)
	at dotty.tools.repl.Main$.main(Main.scala:6)
	at dotty.tools.repl.Main.main(Main.scala)

---

This on the other hand does not crash:

scala> type Foo[F[_]] = [X] =>> X match { 
     |   case F[a] => F[Tuple1[a]]
     | }

scala> (Set(1,2,3), List("a","b")).map([A] => (a: A) => a match {
     |   case it: Iterable[x] => it.map(Tuple1(_)).asInstanceOf[Foo[Iterable][A]]
     | })
val res1: (Foo[Iterable][Set[Int]], Foo[Iterable][List[String]]) = (Set((1,), (2,), (3,)),List((a,), (b,)))

scala> val tup: (Iterable[Tuple1[Int]], Iterable[Tuple1[String]]) = res1
val tup: (Iterable[Tuple1[Int]], Iterable[Tuple1[String]]) = (Set((1,), (2,), (3,)),List((a,), (b,)))