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Matching on abstract tuples causes dotty to stackoverflow #8905

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Matching on abstract tuples causes dotty to stackoverflow#8905
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OlivierBlanvillain
Labels
itype:bug
@yilinwei

Description

@yilinwei
yilinwei
opened on May 7, 2020

Minimized code

object Example {

  def failsHorribly[T1 <: Tuple, T2 <: Tuple](f: () => Either[Unit, Tuple.Concat[T1, T2]])(using size: Tuple.Size[T1]): () => Either[Unit, T2] = {
    () => {
      f() match {
        case Left(_) => Left(())
        case Right(item) => Right(item.drop(size).asInstanceOf[T2])
      }
    }
  }
}

Output

...
        at dotty.tools.dotc.core.Types$TypeMap.mapOver(Types.scala:4956)
        at dotty.tools.dotc.core.TypeOps$AbstractTypeMap$1.apply(TypeOps.scala:548)
        at dotty.tools.dotc.core.Types$TypeMap.mapOverLambda$1(Types.scala:4934)
        at dotty.tools.dotc.core.Types$TypeMap.mapOver(Types.scala:4936)
        at dotty.tools.dotc.core.TypeOps$AbstractTypeMap$1.apply(TypeOps.scala:548)
        at dotty.tools.dotc.core.TypeOps$AbstractTypeMap$1.apply(TypeOps.scala:541)
        at dotty.tools.dotc.core.Types$TypeMap.op$4(Types.scala:4895)
        at dotty.tools.dotc.core.Types$TypeMap.mapArgs$1(Types.scala:4895)
        at dotty.tools.dotc.core.Types$TypeMap.mapArgs$1(Types.scala:4897)
        at dotty.tools.dotc.core.Types$TypeMap.mapOver(Types.scala:4903)
        at dotty.tools.dotc.core.TypeOps$AbstractTypeMap$1.apply(TypeOps.scala:548)
        at dotty.tools.dotc.core.Types$TypeMap.op$4(Types.scala:4895)
        at dotty.tools.dotc.core.Types$TypeMap.mapArgs$1(Types.scala:4895)
        at dotty.tools.dotc.core.Types$TypeMap.mapArgs$1(Types.scala:4897)
        at dotty.tools.dotc.core.Types$TypeMap.mapOver(Types.scala:4903)
        at dotty.tools.dotc.core.TypeOps$AbstractTypeMap$1.apply(TypeOps.scala:548)
        at dotty.tools.dotc.core.Types$TypeMap.mapOverLambda$1(Types.scala:4934)
        at dotty.tools.dotc.core.Types$TypeMap.mapOver(Types.scala:4936)
        at dotty.tools.dotc.core.TypeOps$AbstractTypeMap$1.apply(TypeOps.scala:548)
        at dotty.tools.dotc.core.TypeOps$AbstractTypeMap$1.apply(TypeOps.scala:530)
        at scala.collection.immutable.List.mapConserve(List.scala:472)
        at dotty.tools.dotc.core.Types$TypeMap.mapOver(Types.scala:4956)
        at dotty.tools.dotc.core.TypeOps$AbstractTypeMap$1.apply(TypeOps.scala:548)
        at dotty.tools.dotc.core.Types$TypeMap.mapOverLambda$1(Types.scala:4934)
        at dotty.tools.dotc.core.Types$TypeMap.mapOver(Types.scala:4936)
        at dotty.tools.dotc.core.TypeOps$AbstractTypeMap$1.apply(TypeOps.scala:548)
        at dotty.tools.dotc.core.TypeOps$AbstractTypeMap$1.apply(TypeOps.scala:541)
        at dotty.tools.dotc.core.Types$TypeMap.op$4(Types.scala:4895)
        at dotty.tools.dotc.core.Types$TypeMap.mapArgs$1(Types.scala:4895)
        at dotty.tools.dotc.core.Types$TypeMap.mapArgs$1(Types.scala:4897)
        at dotty.tools.dotc.core.Types$TypeMap.mapOver(Types.scala:4903)
        at dotty.tools.dotc.core.TypeOps$AbstractTypeMap$1.apply(TypeOps.scala:548)
        at dotty.tools.dotc.core.Types$TypeMap.op$4(Types.scala:4895)
        at dotty.tools.dotc.core.Types$TypeMap.mapArgs$1(Types.scala:4895)
        at dotty.tools.dotc.core.Types$TypeMap.mapArgs$1(Types.scala:4897)
        at dotty.tools.dotc.core.Types$TypeMap.mapOver(Types.scala:4903)
        at dotty.tools.dotc.core.TypeOps$AbstractTypeMap$1.apply(TypeOps.scala:548)
        at dotty.tools.dotc.core.Types$TypeMap.mapOverLambda$1(Types.scala:4934)
        at dotty.tools.dotc.core.Types$TypeMap.mapOver(Types.scala:4936)
        at dotty.tools.dotc.core.TypeOps$AbstractTypeMap$1.apply(TypeOps.scala:548)
        at dotty.tools.dotc.core.TypeOps$AbstractTypeMap$1.apply(TypeOps.scala:530)
        at scala.collection.immutable.List.mapConserve(List.scala:472)
        at dotty.tools.dotc.core.Types$TypeMap.mapOver(Types.scala:4956)
        at dotty.tools.dotc.core.TypeOps$AbstractTypeMap$1.apply(TypeOps.scala:548)
        at dotty.tools.dotc.core.Types$TypeMap.mapOverLambda$1(Types.scala:4934)
        at dotty.tools.dotc.core.Types$TypeMap.mapOver(Types.scala:4936)
        at dotty.tools.dotc.core.TypeOps$AbstractTypeMap$1.apply(TypeOps.scala:548)
        at dotty.tools.dotc.core.TypeOps$AbstractTypeMap$1.apply(TypeOps.scala:541)
        at dotty.tools.dotc.core.Types$TypeMap.op$4(Types.scala:4895)
        at dotty.tools.dotc.core.Types$TypeMap.mapArgs$1(Types.scala:4895)
        at dotty.tools.dotc.core.Types$TypeMap.mapArgs$1(Types.scala:4897)
        at dotty.tools.dotc.core.Types$TypeMap.mapOver(Types.scala:4903)
        at dotty.tools.dotc.core.TypeOps$AbstractTypeMap$1.apply(TypeOps.scala:548)
        at dotty.tools.dotc.core.Types$TypeMap.op$4(Types.scala:4895)
        at dotty.tools.dotc.core.Types$TypeMap.mapArgs$1(Types.scala:4895)
        at dotty.tools.dotc.core.Types$TypeMap.mapArgs$1(Types.scala:4897)
        at dotty.tools.dotc.core.Types$TypeMap.mapOver(Types.scala:4903)
        at dotty.tools.dotc.core.TypeOps$AbstractTypeMap$1.apply(TypeOps.scala:548)
        at dotty.tools.dotc.core.Types$TypeMap.mapOverLambda$1(Types.scala:4934)
        at dotty.tools.dotc.core.Types$TypeMap.mapOver(Types.scala:4936)
        at dotty.tools.dotc.core.TypeOps$AbstractTypeMap$1.apply(TypeOps.scala:548)
        at dotty.tools.dotc.core.TypeOps$AbstractTypeMap$1.apply(TypeOps.scala:530)
        at scala.collection.immutable.List.mapConserve(List.scala:472)
        at dotty.tools.dotc.core.Types$TypeMap.mapOver(Types.scala:4956)
        at dotty.tools.dotc.core.TypeOps$AbstractTypeMap$1.apply(TypeOps.scala:548)
        at dotty.tools.dotc.core.Types$TypeMap.mapOverLambda$1(Types.scala:4934)
        at dotty.tools.dotc.core.Types$TypeMap.mapOver(Types.scala:4936)
        at dotty.tools.dotc.core.TypeOps$AbstractTypeMap$1.apply(TypeOps.scala:548)
        at dotty.tools.dotc.core.TypeOps$AbstractTypeMap$1.apply(TypeOps.scala:541)
        at dotty.tools.dotc.core.TypeOps.instantiateToSubType(TypeOps.scala:608)
        at dotty.tools.dotc.core.TypeOps.refineUsingParent(TypeOps.scala:509)
        at dotty.tools.dotc.core.Contexts$Context.refineUsingParent(Contexts.scala:78)
        at dotty.tools.dotc.transform.patmat.SpaceEngine.$anonfun$4(Space.scala:608)
        at scala.collection.immutable.List.map(List.scala:246)
        at dotty.tools.dotc.transform.patmat.SpaceEngine.decompose(Space.scala:620)
        at dotty.tools.dotc.transform.patmat.SpaceLogic.tryDecompose1$2(Space.scala:193)
        at dotty.tools.dotc.transform.patmat.SpaceLogic.op$3(Space.scala:203)
        at dotty.tools.dotc.transform.patmat.SpaceLogic.intersect(Space.scala:229)
        at dotty.tools.dotc.transform.patmat.SpaceEngine.intersect(Space.scala:311)
        at dotty.tools.dotc.transform.patmat.SpaceLogic.op$9$$anonfun$1(Space.scala:198)
        at scala.collection.immutable.List.map(List.scala:250)
        at dotty.tools.dotc.transform.patmat.SpaceLogic.op$3(Space.scala:198)
        at dotty.tools.dotc.transform.patmat.SpaceLogic.intersect(Space.scala:229)
        at dotty.tools.dotc.transform.patmat.SpaceEngine.intersect(Space.scala:311)
        at dotty.tools.dotc.transform.patmat.SpaceLogic.op$18$$anonfun$4(Space.scala:266)
        at scala.collection.immutable.List.exists(List.scala:395)
        at dotty.tools.dotc.transform.patmat.SpaceLogic.op$4(Space.scala:266)
        at dotty.tools.dotc.transform.patmat.SpaceLogic.minus(Space.scala:275)
        at dotty.tools.dotc.transform.patmat.SpaceEngine.minus(Space.scala:311)
        at dotty.tools.dotc.transform.patmat.SpaceLogic.op$4(Space.scala:246)
        at dotty.tools.dotc.transform.patmat.SpaceLogic.minus(Space.scala:275)
        at dotty.tools.dotc.transform.patmat.SpaceEngine.minus(Space.scala:311)
        at dotty.tools.dotc.transform.patmat.SpaceLogic.op$17$$anonfun$3(Space.scala:252)
        at scala.collection.immutable.List.map(List.scala:250)
        at dotty.tools.dotc.transform.patmat.SpaceLogic.op$4(Space.scala:252)
        at dotty.tools.dotc.transform.patmat.SpaceLogic.minus(Space.scala:275)
        at dotty.tools.dotc.transform.patmat.SpaceEngine.minus(Space.scala:311)
        at dotty.tools.dotc.transform.patmat.SpaceLogic.op$16$$anonfun$2(Space.scala:250)
        at scala.collection.LinearSeqOps.foldLeft(LinearSeq.scala:168)
        at scala.collection.LinearSeqOps.foldLeft$(LinearSeq.scala:164)
        at scala.collection.immutable.List.foldLeft(List.scala:79)
        at dotty.tools.dotc.transform.patmat.SpaceLogic.op$4(Space.scala:250)
        at dotty.tools.dotc.transform.patmat.SpaceLogic.minus(Space.scala:275)
        at dotty.tools.dotc.transform.patmat.SpaceEngine.minus(Space.scala:311)
        at dotty.tools.dotc.transform.patmat.SpaceEngine.checkExhaustivity(Space.scala:829)
        at dotty.tools.dotc.transform.PatternMatcher.transformMatch(PatternMatcher.scala:45)
        at dotty.tools.dotc.transform.MegaPhase.goMatch(MegaPhase.scala:746)
        at dotty.tools.dotc.transform.MegaPhase.transformUnnamed$1(MegaPhase.scala:345)
        at dotty.tools.dotc.transform.MegaPhase.transformTree(MegaPhase.scala:396)
        at dotty.tools.dotc.transform.MegaPhase.transformUnnamed$1(MegaPhase.scala:287)
        at dotty.tools.dotc.transform.MegaPhase.transformTree(MegaPhase.scala:396)
        at dotty.tools.dotc.transform.MegaPhase.mapDefDef$1(MegaPhase.scala:245)
        at dotty.tools.dotc.transform.MegaPhase.transformNamed$1(MegaPhase.scala:248)
        at dotty.tools.dotc.transform.MegaPhase.transformTree(MegaPhase.scala:394)
        at dotty.tools.dotc.transform.MegaPhase.transformStat$2(MegaPhase.scala:404)
        at dotty.tools.dotc.transform.MegaPhase.$anonfun$1(MegaPhase.scala:409)
        at scala.collection.immutable.List.mapConserve(List.scala:472)
        at dotty.tools.dotc.transform.MegaPhase.transformStats(MegaPhase.scala:409)
        at dotty.tools.dotc.transform.MegaPhase.transformUnnamed$1(MegaPhase.scala:286)
        at dotty.tools.dotc.transform.MegaPhase.transformTree(MegaPhase.scala:396)
        at dotty.tools.dotc.transform.MegaPhase.transformUnnamed$1(MegaPhase.scala:287)
        at dotty.tools.dotc.transform.MegaPhase.transformTree(MegaPhase.scala:396)
        at dotty.tools.dotc.transform.MegaPhase.mapDefDef$1(MegaPhase.scala:245)
        at dotty.tools.dotc.transform.MegaPhase.transformNamed$1(MegaPhase.scala:248)
        at dotty.tools.dotc.transform.MegaPhase.transformTree(MegaPhase.scala:394)
        at dotty.tools.dotc.transform.MegaPhase.transformStat$2(MegaPhase.scala:404)
        at dotty.tools.dotc.transform.MegaPhase.$anonfun$1(MegaPhase.scala:409)
        at scala.collection.immutable.List.mapConserve(List.scala:472)
        at dotty.tools.dotc.transform.MegaPhase.transformStats(MegaPhase.scala:409)
        at dotty.tools.dotc.transform.MegaPhase.transformUnnamed$1(MegaPhase.scala:339)
        at dotty.tools.dotc.transform.MegaPhase.transformTree(MegaPhase.scala:396)
        at dotty.tools.dotc.transform.MegaPhase.transformNamed$1(MegaPhase.scala:251)
        at dotty.tools.dotc.transform.MegaPhase.transformTree(MegaPhase.scala:394)
        at dotty.tools.dotc.transform.MegaPhase.transformStat$2(MegaPhase.scala:404)
        at dotty.tools.dotc.transform.MegaPhase.$anonfun$1(MegaPhase.scala:409)
        at scala.collection.immutable.List.mapConserve(List.scala:472)
        at dotty.tools.dotc.transform.MegaPhase.transformStats(MegaPhase.scala:409)
        at dotty.tools.dotc.transform.MegaPhase.mapPackage$1(MegaPhase.scala:356)
        at dotty.tools.dotc.transform.MegaPhase.transformUnnamed$1(MegaPhase.scala:359)
        at dotty.tools.dotc.transform.MegaPhase.transformTree(MegaPhase.scala:396)
        at dotty.tools.dotc.transform.MegaPhase.transformUnit(MegaPhase.scala:415)
        at dotty.tools.dotc.transform.MegaPhase.run(MegaPhase.scala:427)
        at dotty.tools.dotc.core.Phases$Phase.runOn$$anonfun$1(Phases.scala:318)
        at scala.collection.immutable.List.map(List.scala:246)
        at dotty.tools.dotc.core.Phases$Phase.runOn(Phases.scala:319)
        at dotty.tools.dotc.Run.runPhases$4$$anonfun$4(Run.scala:165)
        at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:15)
        at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:10)
        at scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1323)
        at dotty.tools.dotc.Run.runPhases$5(Run.scala:175)
        at dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:183)
        at dotty.runtime.function.JFunction0$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:190)
        at dotty.tools.dotc.Run.compileSources(Run.scala:127)
        at dotty.tools.dotc.Run.compile(Run.scala:110)
        at dotty.tools.dotc.Driver.doCompile(Driver.scala:38)
        at dotty.tools.dotc.Driver.process(Driver.scala:194)
        at dotty.tools.dotc.Driver.process(Driver.scala:163)
        at dotty.tools.dotc.Driver.process(Driver.scala:175)
        at dotty.tools.dotc.Driver.main(Driver.scala:202)
        at dotty.tools.dotc.Main.main(Main.scala)

Expectation

Probably shouldn't stackoverflow.

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