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kory33 opened this issue Nov 30, 2018 · 3 comments
Closed

ClassCastException when typechecking dependent function value with certain return type #5550

kory33 opened this issue Nov 30, 2018 · 3 comments

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@kory33
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kory33 commented Nov 30, 2018 •
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This can be reproduced in both 0.12.0-bin-20181129-2ec79d1-NIGHTLY and 0.11.0-RC1

object Test {
  trait Wrap { type T }

  // this compiles
  def test11[A](ev: (e: Wrap) => List[e.T]): List[A] = ev(new Wrap { type T = A })
  def test12[A]: List[A] = test11 { w: Wrap => List() }

  // but this does not when the commented code is included (compiler crashes with stack trace)
  def test21[F[_], A](ev: (e: Wrap) => F[e.T]): F[A] = ??? // ev(new Wrap { type T = A })
  def test22[A]: List[A] = test21[List, A] { w: Wrap => List() }
}

Stack trace:

java.lang.ClassCastException: dotty.tools.dotc.core.Types$LambdaParam cannot be cast to dotty.tools.dotc.core.Symbols$Symbol
        at dotty.tools.dotc.core.TypeComparer.compareCaptured$1(TypeComparer.scala:990)
        at dotty.tools.dotc.core.TypeComparer.isSubArg$1(TypeComparer.scala:1002)
        at dotty.tools.dotc.core.TypeComparer.isSubArgs(TypeComparer.scala:1011)
        at dotty.tools.dotc.core.TypeComparer.isMatchingApply$1(TypeComparer.scala:743)
        at dotty.tools.dotc.core.TypeComparer.compareAppliedType2$1(TypeComparer.scala:846)
        at dotty.tools.dotc.core.TypeComparer.thirdTry$1(TypeComparer.scala:428)
        at dotty.tools.dotc.core.TypeComparer.secondTry$1(TypeComparer.scala:388)
        at dotty.tools.dotc.core.TypeComparer.firstTry$1(TypeComparer.scala:307)
        at dotty.tools.dotc.core.TypeComparer.recur(TypeComparer.scala:942)
        at dotty.tools.dotc.core.TypeComparer.isSubType(TypeComparer.scala:132)
        at dotty.tools.dotc.core.TypeComparer.isSubType(TypeComparer.scala:139)
        at dotty.tools.dotc.core.TypeComparer.compareMethod$1(TypeComparer.scala:562)
        at dotty.tools.dotc.core.TypeComparer.thirdTry$1(TypeComparer.scala:565)
        at dotty.tools.dotc.core.TypeComparer.secondTry$1(TypeComparer.scala:388)
        at dotty.tools.dotc.core.TypeComparer.firstTry$1(TypeComparer.scala:307)
        at dotty.tools.dotc.core.TypeComparer.recur(TypeComparer.scala:942)
        at dotty.tools.dotc.core.TypeComparer.isSubType(TypeComparer.scala:132)
        at dotty.tools.dotc.core.TypeComparer.isSubType(TypeComparer.scala:139)
        at dotty.tools.dotc.core.ConstraintHandling.isSubTypeWhenFrozen(ConstraintHandling.scala:185)
        at dotty.tools.dotc.core.Types$Type.frozen_$less$colon$less(Types.scala:831)
        at dotty.tools.dotc.core.Types$Type.overrides(Types.scala:867)
        at dotty.tools.dotc.core.Denotations$Denotation.prefer$2(Denotations.scala:520)
        at dotty.tools.dotc.core.Denotations$Denotation.mergeSingleDenot$1(Denotations.scala:530)
        at dotty.tools.dotc.core.Denotations$Denotation.mergeDenot$1(Denotations.scala:456)
        at dotty.tools.dotc.core.Denotations$Denotation.$amp(Denotations.scala:562)
        at dotty.tools.dotc.core.Types$Type.goRefined$1(Types.scala:653)
        at dotty.tools.dotc.core.Types$Type.go$1(Types.scala:569)
        at dotty.tools.dotc.core.Types$Type.findMember(Types.scala:702)
        at dotty.tools.dotc.core.Types$Type.memberExcluding(Types.scala:532)
        at dotty.tools.dotc.core.Types$Type.member(Types.scala:518)
        at dotty.tools.dotc.typer.ProtoTypes$SelectionProto.isMatchedBy(ProtoTypes.scala:135)
        at dotty.tools.dotc.core.TypeComparer.isMatchedByProto(TypeComparer.scala:1206)
        at dotty.tools.dotc.core.TypeComparer.firstTry$1(TypeComparer.scala:234)
        at dotty.tools.dotc.core.TypeComparer.recur(TypeComparer.scala:942)
        at dotty.tools.dotc.core.TypeComparer.isSubType(TypeComparer.scala:132)
        at dotty.tools.dotc.core.TypeComparer.isSubType(TypeComparer.scala:139)
        at dotty.tools.dotc.core.TypeComparer.topLevelSubType(TypeComparer.scala:118)
        at dotty.tools.dotc.core.Types$Type.$less$colon$less(Types.scala:826)
        at dotty.tools.dotc.typer.Typer.adaptNoArgsOther$4(Typer.scala:2487)
        at dotty.tools.dotc.typer.Typer.adaptNoArgs$1(Typer.scala:2549)
        at dotty.tools.dotc.typer.Typer.adapt1(Typer.scala:2683)
        at dotty.tools.dotc.typer.Typer.adapt(Typer.scala:2224)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:1992)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2004)
        at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:2067)
        at dotty.tools.dotc.typer.Typer.typeSelectOnTerm$1(Typer.scala:432)
        at dotty.tools.dotc.typer.Typer.typedSelect(Typer.scala:461)
        at dotty.tools.dotc.typer.Typer.tryApply$1(Typer.scala:2139)
        at dotty.tools.dotc.typer.Typer.tryInsertApplyOrImplicit$$anonfun$2(Typer.scala:2157)
        at dotty.tools.dotc.typer.Typer.tryEither(Typer.scala:2075)
        at dotty.tools.dotc.typer.Typer.tryInsertApplyOrImplicit(Typer.scala:2166)
        at dotty.tools.dotc.typer.Typer.adaptToArgs$1(Typer.scala:2295)
        at dotty.tools.dotc.typer.Typer.adapt1(Typer.scala:2678)
        at dotty.tools.dotc.typer.Typer.adapt(Typer.scala:2224)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:1992)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2004)
        at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:2067)
        at dotty.tools.dotc.typer.Applications.realApply$1(Applications.scala:743)
        at dotty.tools.dotc.typer.Applications.typedApply(Applications.scala:842)
        at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:1907)
        at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:1961)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:1992)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2004)
        at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:2067)
        at dotty.tools.dotc.typer.Typer.typedDefDef(Typer.scala:1507)
        at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:1894)
        at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:1960)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:1992)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2004)
        at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:2023)
        at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:2056)
        at dotty.tools.dotc.typer.Typer.typedClassDef(Typer.scala:1615)
        at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:1897)
        at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:1960)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:1992)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2004)
        at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:2023)
        at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:2056)
        at dotty.tools.dotc.typer.Typer.typedPackageDef(Typer.scala:1733)
        at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:1939)
        at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:1961)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:1992)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2004)
        at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:2067)
        at dotty.tools.dotc.typer.FrontEnd.typeCheck$$anonfun$1(FrontEnd.scala:60)
        at scala.compat.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:12)
        at dotty.tools.dotc.typer.FrontEnd.monitor(FrontEnd.scala:34)
        at dotty.tools.dotc.typer.FrontEnd.typeCheck(FrontEnd.scala:64)
        at dotty.tools.dotc.typer.FrontEnd.runOn$$anonfun$2(FrontEnd.scala:88)
        at scala.compat.java8.JProcedure1.apply(JProcedure1.java:18)
        at scala.compat.java8.JProcedure1.apply(JProcedure1.java:10)
        at scala.collection.immutable.List.foreach(List.scala:388)
        at dotty.tools.dotc.typer.FrontEnd.runOn(FrontEnd.scala:88)
        at dotty.tools.dotc.Run.runPhases$4$$anonfun$4(Run.scala:172)
        at scala.compat.java8.JProcedure1.apply(JProcedure1.java:18)
        at scala.compat.java8.JProcedure1.apply(JProcedure1.java:10)
        at scala.collection.IndexedSeqOptimized.foreach(IndexedSeqOptimized.scala:32)
        at scala.collection.IndexedSeqOptimized.foreach$(IndexedSeqOptimized.scala:29)
        at scala.collection.mutable.ArrayOps$ofRef.foreach(ArrayOps.scala:194)
        at dotty.tools.dotc.Run.runPhases$5(Run.scala:184)
        at dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:192)
        at scala.compat.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:12)
        at dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:90)
        at dotty.tools.dotc.Run.compileUnits(Run.scala:199)
        at dotty.tools.dotc.Run.compileSources(Run.scala:134)
        at dotty.tools.dotc.Run.compile(Run.scala:118)
        at dotty.tools.dotc.Driver.doCompile(Driver.scala:33)
        at dotty.tools.dotc.Driver.process(Driver.scala:166)
        at xsbt.CachedCompilerImpl.run(CompilerInterface.scala:61)
        at xsbt.CachedCompilerImpl.run(CompilerInterface.scala:51)
        at xsbt.CompilerInterface.run(CompilerInterface.scala:35)
        at sun.reflect.GeneratedMethodAccessor44.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        at sbt.internal.inc.AnalyzingCompiler.call(AnalyzingCompiler.scala:237)
        at sbt.internal.inc.AnalyzingCompiler.compile(AnalyzingCompiler.scala:111)
        at sbt.internal.inc.AnalyzingCompiler.compile(AnalyzingCompiler.scala:90)
        at sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$3(MixedAnalyzingCompiler.scala:83)
        at scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:12)
        at sbt.internal.inc.MixedAnalyzingCompiler.timed(MixedAnalyzingCompiler.scala:134)
        at sbt.internal.inc.MixedAnalyzingCompiler.compileScala$1(MixedAnalyzingCompiler.scala:74)
        at sbt.internal.inc.MixedAnalyzingCompiler.compile(MixedAnalyzingCompiler.scala:117)
        at sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1(IncrementalCompilerImpl.scala:305)
        at sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1$adapted(IncrementalCompilerImpl.scala:305)
        at sbt.internal.inc.Incremental$.doCompile(Incremental.scala:101)
        at sbt.internal.inc.Incremental$.$anonfun$compile$4(Incremental.scala:82)
        at sbt.internal.inc.IncrementalCommon.recompileClasses(IncrementalCommon.scala:110)
        at sbt.internal.inc.IncrementalCommon.cycle(IncrementalCommon.scala:57)
        at sbt.internal.inc.Incremental$.$anonfun$compile$3(Incremental.scala:84)
        at sbt.internal.inc.Incremental$.manageClassfiles(Incremental.scala:129)
        at sbt.internal.inc.Incremental$.compile(Incremental.scala:75)
        at sbt.internal.inc.IncrementalCompile$.apply(Compile.scala:61)
        at sbt.internal.inc.IncrementalCompilerImpl.compileInternal(IncrementalCompilerImpl.scala:309)
        at sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileIncrementally$1(IncrementalCompilerImpl.scala:267)
        at sbt.internal.inc.IncrementalCompilerImpl.handleCompilationError(IncrementalCompilerImpl.scala:158)
        at sbt.internal.inc.IncrementalCompilerImpl.compileIncrementally(IncrementalCompilerImpl.scala:237)
        at sbt.internal.inc.IncrementalCompilerImpl.compile(IncrementalCompilerImpl.scala:68)
        at sbt.Defaults$.compileIncrementalTaskImpl(Defaults.scala:1430)
        at sbt.Defaults$.$anonfun$compileIncrementalTask$1(Defaults.scala:1404)
        at scala.Function1.$anonfun$compose$1(Function1.scala:44)
        at sbt.internal.util.$tilde$greater.$anonfun$$u2219$1(TypeFunctions.scala:39)
        at sbt.std.Transform$$anon$4.work(System.scala:66)
        at sbt.Execute.$anonfun$submit$2(Execute.scala:262)
        at sbt.internal.util.ErrorHandling$.wideConvert(ErrorHandling.scala:16)
        at sbt.Execute.work(Execute.scala:271)
        at sbt.Execute.$anonfun$submit$1(Execute.scala:262)
        at sbt.ConcurrentRestrictions$$anon$4.$anonfun$submitValid$1(ConcurrentRestrictions.scala:174)
        at sbt.CompletionService$$anon$2.call(CompletionService.scala:36)
        at java.util.concurrent.FutureTask.run(FutureTask.java:266)
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
        at java.util.concurrent.FutureTask.run(FutureTask.java:266)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
        at java.lang.Thread.run(Thread.java:748)
@kory33
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kory33 commented Nov 30, 2018

This seems to happen not only when invoking such a function ev, but also when merely evaluating ev.apply(without any application), as in

    def test21[F[_], A](ev: (e: Wrap) => F[e.T]): F[A] = { ev.apply; ??? }

This is sufficient to crash the compiler and the same stack trace was produced.

@kory33 kory33 changed the title ClassCastException when typechecking invocation of dependent function value with certain return type ClassCastException when typechecking dependent function value with certain return type Nov 30, 2018
@kory33
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kory33 commented Dec 11, 2018

A minified version of the code is as follows:

object Test {
  type Obj // this can be concrete as well
  type F[_] // when this is abstract, compiler crashes
  type Forall[G[_]] = (x: Obj) => G[x.type]

  def idFn(ag: Forall[F]): Forall[F] = ag // crashes while checking ag.type <:< Forall[F]
}

The exception produced is the same as that in #4376.

@kory33
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kory33 commented Dec 13, 2018

This would be a duplicate of #4382, since a type (x: Obj) => F[x.type] expands to Function1[Obj, F[_ <: Obj]] { def apply(x: Obj): F[x.type] } and F[_ <: Obj] is an application of wildcard to an abstract type constructor F.

@kory33 kory33 closed this as completed Dec 13, 2018
@b-studios b-studios mentioned this issue Jan 30, 2019
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