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assertion failure in typer with nested match and existentials #1357

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scabug opened this issue Sep 20, 2008 · 6 comments
Closed

assertion failure in typer with nested match and existentials #1357

scabug opened this issue Sep 20, 2008 · 6 comments
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@odersky
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2.8.0

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@scabug
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scabug commented Sep 20, 2008

This occurred against 2.7.2 RC2 (and RC1). See attached file for code.

java.lang.AssertionError: assertion failed: NonEmptyCons((head @ *), (tail @ *)) ==> NonEmptyCons.unapplyNothing, Nothing ((head @ *), (tail @ *)), pt = ?
at scala.Predef$$.assert(Predef.scala:92)
at scala.tools.nsc.typechecker.Typers$$Typer.doTypedApply(Typers.scala:1892)
at scala.tools.nsc.typechecker.Typers$$Typer.doTypedApply(Typers.scala:1811)
at scala.tools.nsc.typechecker.Typers$$Typer.typedApply$$1(Typers.scala:2619)
at scala.tools.nsc.typechecker.Typers$$Typer.typed1(Typers.scala:3219)
at scala.tools.nsc.typechecker.Typers$$Typer.typed(Typers.scala:3323)
at scala.tools.nsc.typechecker.Typers$$Typer.typedPattern(Typers.scala:3390)
at scala.tools.nsc.typechecker.Typers$$Typer.typedCase(Typers.scala:1419)
at scala.tools.nsc.typechecker.Typers$$Typer$$$$anonfun$$typedCases$$1.apply(Typers.scala:1442)
at scala.tools.nsc.typechecker.Typers$$Typer$$$$anonfun$$typedCases$$1.apply(Typers.scala:1440)
at scala.List$$.loop$$1(List.scala:293)
at scala.List$$.mapConserve(List.scala:310)
at scala.tools.nsc.typechecker.Typers$$Typer.typedCases(Typers.scala:1440)
at scala.tools.nsc.typechecker.Typers$$Typer.typed1(Typers.scala:3135)
at scala.tools.nsc.typechecker.Typers$$Typer.typed(Typers.scala:3323)
at scala.tools.nsc.typechecker.Typers$$Typer.typedBlock(Typers.scala:1405)
at scala.tools.nsc.typechecker.Typers$$Typer.typed1(Typers.scala:3083)
at scala.tools.nsc.typechecker.Typers$$Typer.typed(Typers.scala:3323)
at scala.tools.nsc.typechecker.Typers$$Typer.typed(Typers.scala:3371)
at scala.tools.nsc.typechecker.Typers$$Typer.typedCase(Typers.scala:1422)
at scala.tools.nsc.typechecker.Typers$$Typer$$$$anonfun$$typedCases$$1.apply(Typers.scala:1442)
at scala.tools.nsc.typechecker.Typers$$Typer$$$$anonfun$$typedCases$$1.apply(Typers.scala:1440)
at scala.List$$.loop$$1(List.scala:293)
at scala.List$$.mapConserve(List.scala:310)
at scala.tools.nsc.typechecker.Typers$$Typer.typedCases(Typers.scala:1440)
at scala.tools.nsc.typechecker.Typers$$Typer.typed1(Typers.scala:3135)
at scala.tools.nsc.typechecker.Typers$$Typer.typed(Typers.scala:3323)
at scala.tools.nsc.typechecker.Typers$$Typer.typed(Typers.scala:3371)
at scala.tools.nsc.typechecker.Typers$$Typer.transformedOrTyped(Typers.scala:3429)
at scala.tools.nsc.typechecker.Typers$$Typer.typedDefDef(Typers.scala:1342)
at scala.tools.nsc.typechecker.Typers$$Typer.typed1(Typers.scala:3059)
at scala.tools.nsc.typechecker.Typers$$Typer.typed(Typers.scala:3323)
at scala.tools.nsc.typechecker.Typers$$Typer.typed(Typers.scala:3360)
at scala.tools.nsc.typechecker.Typers$$Typer.typedStat$$1(Typers.scala:1570)
at scala.tools.nsc.typechecker.Typers$$Typer$$$$anonfun$$19.apply(Typers.scala:1615)
at scala.tools.nsc.typechecker.Typers$$Typer$$$$anonfun$$19.apply(Typers.scala:1615)
at scala.List$$.loop$$1(List.scala:293)
at scala.List$$.mapConserve(List.scala:310)
at scala.List$$.loop$$1(List.scala:297)
at scala.List$$.mapConserve(List.scala:310)
at scala.List$$.loop$$1(List.scala:297)
at scala.List$$.mapConserve(List.scala:310)
at scala.tools.nsc.typechecker.Typers$$Typer.typedStats(Typers.scala:1615)
at scala.tools.nsc.typechecker.Typers$$Typer.typedTemplate(Typers.scala:1193)
at scala.tools.nsc.typechecker.Typers$$Typer.typedModuleDef(Typers.scala:1086)
at scala.tools.nsc.typechecker.Typers$$Typer.typed1(Typers.scala:3053)
at scala.tools.nsc.typechecker.Typers$$Typer.typed(Typers.scala:3323)
at scala.tools.nsc.typechecker.Typers$$Typer.typed(Typers.scala:3360)
at scala.tools.nsc.typechecker.Typers$$Typer.typedStat$$1(Typers.scala:1570)
at scala.tools.nsc.typechecker.Typers$$Typer$$$$anonfun$$19.apply(Typers.scala:1615)
at scala.tools.nsc.typechecker.Typers$$Typer$$$$anonfun$$19.apply(Typers.scala:1615)
at scala.List$$.loop$$1(List.scala:293)
at scala.List$$.mapConserve(List.scala:310)
at scala.List$$.loop$$1(List.scala:297)
at scala.List$$.mapConserve(List.scala:310)
at scala.List$$.loop$$1(List.scala:297)
at scala.List$$.mapConserve(List.scala:310)
at scala.List$$.loop$$1(List.scala:297)
at scala.List$$.mapConserve(List.scala:310)
at scala.List$$.loop$$1(List.scala:297)
at scala.List$$.mapConserve(List.scala:310)
at scala.List$$.loop$$1(List.scala:297)
at scala.List$$.mapConserve(List.scala:310)
at scala.tools.nsc.typechecker.Typers$$Typer.typedStats(Typers.scala:1615)
at scala.tools.nsc.typechecker.Typers$$Typer.typed1(Typers.scala:3046)
at scala.tools.nsc.typechecker.Typers$$Typer.typed(Typers.scala:3323)
at scala.tools.nsc.typechecker.Typers$$Typer.typed(Typers.scala:3360)
at scala.tools.nsc.typechecker.Analyzer$$typerFactory$$$$anon$$2.apply(Analyzer.scala:40)
at scala.tools.nsc.Global$$GlobalPhase.applyPhase(Global.scala:268)
at scala.tools.nsc.Global$$GlobalPhase$$$$anonfun$$run$$1.apply(Global.scala:247)
at scala.tools.nsc.Global$$GlobalPhase$$$$anonfun$$run$$1.apply(Global.scala:247)
at scala.Iterator$$class.foreach(Iterator.scala:410)
at scala.collection.mutable.ListBuffer$$$$anon$$1.foreach(ListBuffer.scala:266)
at scala.tools.nsc.Global$$GlobalPhase.run(Global.scala:247)
at scala.tools.nsc.Global$$Run.compileSources(Global.scala:579)
at scala.tools.nsc.Global$$Run.compile(Global.scala:663)
at scala.tools.ant.Scalac.execute(Scalac.scala:574)
at org.apache.tools.ant.UnknownElement.execute(UnknownElement.java:288)
at sun.reflect.GeneratedMethodAccessor90.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at org.apache.tools.ant.dispatch.DispatchUtils.execute(DispatchUtils.java:106)
at org.apache.tools.ant.Task.perform(Task.java:348)
at org.apache.tools.ant.taskdefs.Sequential.execute(Sequential.java:62)
at org.apache.tools.ant.UnknownElement.execute(UnknownElement.java:288)
at sun.reflect.GeneratedMethodAccessor90.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at org.apache.tools.ant.dispatch.DispatchUtils.execute(DispatchUtils.java:106)
at org.apache.tools.ant.Task.perform(Task.java:348)
at org.apache.tools.ant.taskdefs.MacroInstance.execute(MacroInstance.java:394)
at org.apache.tools.ant.UnknownElement.execute(UnknownElement.java:288)
at sun.reflect.GeneratedMethodAccessor90.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at org.apache.tools.ant.dispatch.DispatchUtils.execute(DispatchUtils.java:106)
at org.apache.tools.ant.Task.perform(Task.java:348)
at org.apache.tools.ant.Target.execute(Target.java:357)
at org.apache.tools.ant.Target.performTasks(Target.java:385)
at org.apache.tools.ant.Project.executeSortedTargets(Project.java:1337)
at org.apache.tools.ant.Project.executeTarget(Project.java:1306)
at org.apache.tools.ant.helper.DefaultExecutor.executeTargets(DefaultExecutor.java:41)
at org.apache.tools.ant.Project.executeTargets(Project.java:1189)
at org.apache.tools.ant.module.bridge.impl.BridgeImpl.run(BridgeImpl.java:273)
at org.apache.tools.ant.module.run.TargetExecutor.run(TargetExecutor.java:486)
at org.netbeans.core.execution.RunClassThread.run(RunClassThread.java:151)
@scabug
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scabug commented Sep 20, 2008

Imported From: https://issues.scala-lang.org/browse/SI-1357?orig=1
Reporter: @eengbrec

@scabug
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scabug commented Sep 20, 2008

@eengbrec said:
// I can't seem to find the "Attach file" button, so here's the code

package constreecompilercrash

object ConsCell {
// Here I'm trying to fake out the compiler into letting me define
// what would more logically be a recursive type. It could be that this
// should be illegal and that's why it is crashing the typer later on.
type BT[+H, +T <: ConsCell[ConsCell[H, T], ConsCell[H, T]]] = ConsCell[H, T]
type BinaryTree[+E] = BT[E, T forSome {type T <: ConsCell[BT[E, T], BT[E, T]]}]

def apply[H, T](h: H, t: T): ConsCell[H, T] = BasicConsCell(h, t)

private case class BasicConsCell[+H, +T](val head: H, val tail: T) extends ConsCell[H, T]
}

sealed trait ConsCell[+H, +T] {
def ::[A](obj: A): ConsCell[A, ConsCell[H, T]] = ConsCell(obj, this)
}

object NonEmptyCons {
def unapply[H, T](c: ConsCell[H, T]): Option[(H, T)] = c match {
case Nil => None
case c: NonEmptyCons[H, T] => Some(c.head, c.tail)
}
}

trait NonEmptyCons[+H, +T] extends ConsCell[H, T] {
def head: H
def tail: T
}

object Nil extends ConsCell[Nothing, Nothing]

object Main {

import ConsCell._

def main(args: Array[String]) {
val t1 = 1 :: Nil // looks like a list, doesn't it?
val t2 = 1 :: ConsCell((2 :: Nil), (3 :: Nil))
walkTree(t1, println)
walkTree(t2, println)
}

def walkTree[E](tree: BinaryTree[E], op: E => Unit): Unit = tree match {
case Nil => ()
case NonEmptyCons(head, tail) => {
op(head)
tail match {
case Nil => ()
case NonEmptyCons(head, tail) => {
walkTree(tail.head, op)
walkTree(tail.tail, op)
}
}
}
}
}

@scabug
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scabug commented Sep 28, 2008

@TiarkRompf said:
Here's a reduced version that also fails. Removing the inner match makes it pass the typer. Replacing the extractors with tuple patterns makes it pass the typer but will cause a crash in ParallelMatching during explicit outer.

object NonEmptyCons {
  def unapply[H, T](c: (H, T)): Option[(H, T)] = Some(c)
}


object Main {

  type BT[+H, +T <: Tuple2[Tuple2[H, T], Tuple2[H, T]]] = Tuple2[H, T]
  
  type BinaryTree[+E] = BT[E, T forSome {type T <: Tuple2[BT[E, T], BT[E, T]]}]

  def foo[E](tree: BinaryTree[E]): Unit = tree match {
    case NonEmptyCons(_, tail) => {
      tail match {
        case NonEmptyCons(_, _) => {
        }
      }
    }
  }
}

@scabug
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scabug commented Oct 6, 2009

@paulp said:
Once again I can't pin which commit fixed a ticket, but the test case is in r18937.

@scabug
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scabug commented Nov 22, 2009

@odersky said:
This re-surfaced with the fix to #2635. The problem seems to be deep in the constraint variable solver which can produce solutions that then do not conform to bounds. A simpler test case is here (in pending/pos/depexists.scala):

 val c: Cell[(a, b)] forSome { type a <: Number; type b <: (a, a) } = null
 val d = c

I defer until we redo the whole approach to constraint solving (which we should do, soon).

@scabug
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scabug commented Jan 20, 2011

@paulp said:
That test has been in files/pos for a year now so I think it's time to close this ticket; I'm sure we'll have no trouble finding issues of more recent vintage.

@scabug scabug closed this as completed May 18, 2011
@scabug scabug added the crash label Apr 6, 2017
@scabug scabug added this to the 2.8.0 milestone Apr 6, 2017
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