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Jasper-M opened this issue Dec 22, 2017 · 0 comments
Closed

NoSuchElementException when passing implicit dependently typed function to method #3692

Jasper-M opened this issue Dec 22, 2017 · 0 comments
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area:typer itype:bug

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@Jasper-M
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Jasper-M commented Dec 22, 2017 •
edited
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class C { type T }

object Main {
  def main(args: Array[String]): Unit = {
    val choose: implicit (c: C) => Set[Int] = Set.empty
    def applyF(f: (c: C) => Set[Int]) = f(new C{type T=Int})
    applyF(choose)
  }
}

Crashes with:

Exception in thread "main" java.util.NoSuchElementException
	at scala.collection.LinearSeqOptimized.last(LinearSeqOptimized.scala:146)
	at scala.collection.LinearSeqOptimized.last$(LinearSeqOptimized.scala:145)
	at scala.collection.immutable.List.last(List.scala:86)
	at dotty.tools.dotc.typer.ProtoTypes$.$anonfun$normalize$1(ProtoTypes.scala:473)
	at dotty.tools.dotc.util.Stats$.track(Stats.scala:35)
	at dotty.tools.dotc.typer.ProtoTypes$.normalize(ProtoTypes.scala:450)
	at dotty.tools.dotc.typer.ErrorReporting$Errors.typeMismatch(ErrorReporting.scala:108)
	at dotty.tools.dotc.typer.Typer.recover$1(Typer.scala:2336)
	at dotty.tools.dotc.typer.Typer.adaptToSubType$1(Typer.scala:2347)
	at dotty.tools.dotc.typer.Typer.adaptNoArgsOther$1(Typer.scala:2240)
	at dotty.tools.dotc.typer.Typer.adaptNoArgs$1(Typer.scala:2285)
	at dotty.tools.dotc.typer.Typer.adaptInterpolated(Typer.scala:2408)
	at dotty.tools.dotc.typer.Typer.$anonfun$adapt$3(Typer.scala:1934)
	at dotty.tools.dotc.reporting.trace$.op1$2(trace.scala:25)
	at dotty.tools.dotc.reporting.trace$.apply(trace.scala:26)
	at dotty.tools.dotc.typer.Typer.$anonfun$adapt$1(Typer.scala:1927)
	at dotty.tools.dotc.util.Stats$.track(Stats.scala:35)
	at dotty.tools.dotc.typer.Typer.adapt(Typer.scala:1927)
	at dotty.tools.dotc.typer.ProtoTypes$FunProto.typedArg(ProtoTypes.scala:244)
	at dotty.tools.dotc.typer.Applications$ApplyToUntyped.typedArg(Applications.scala:639)
	at dotty.tools.dotc.typer.Applications$ApplyToUntyped.typedArg(Applications.scala:637)
	at dotty.tools.dotc.typer.Applications$Application.addTyped$1(Applications.scala:412)
	at dotty.tools.dotc.typer.Applications$Application.matchArgs(Applications.scala:451)
	at dotty.tools.dotc.typer.Applications$Application.init(Applications.scala:233)
	at dotty.tools.dotc.typer.Applications$TypedApply.<init>(Applications.scala:543)
	at dotty.tools.dotc.typer.Applications$ApplyToUntyped.<init>(Applications.scala:638)
	at dotty.tools.dotc.typer.Applications.simpleApply$1(Applications.scala:694)
	at dotty.tools.dotc.typer.Applications.$anonfun$typedApply$7(Applications.scala:719)
	at dotty.tools.dotc.typer.Typer.tryEither(Typer.scala:1830)
	at dotty.tools.dotc.typer.Applications.$anonfun$typedApply$1(Applications.scala:720)
	at dotty.tools.dotc.util.Stats$.track(Stats.scala:35)
	at dotty.tools.dotc.typer.Applications.realApply$1(Applications.scala:664)
	at dotty.tools.dotc.typer.Applications.typedApply(Applications.scala:764)
	at dotty.tools.dotc.typer.Applications.typedApply$(Applications.scala:662)
	at dotty.tools.dotc.typer.Typer.typedApply(Typer.scala:69)
	at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:1698)
	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:1748)
	at dotty.tools.dotc.typer.Typer.$anonfun$typed$2(Typer.scala:1765)
	at dotty.tools.dotc.reporting.trace$.op1$2(trace.scala:25)
	at dotty.tools.dotc.reporting.trace$.apply(trace.scala:26)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:1761)
	at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:1822)
	at dotty.tools.dotc.typer.Typer.$anonfun$typedBlock$1(Typer.scala:634)
	at dotty.tools.dotc.util.Stats$.track(Stats.scala:35)
	at dotty.tools.dotc.typer.Typer.typedBlock(Typer.scala:626)
	at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:1705)
	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:1748)
	at dotty.tools.dotc.typer.Typer.$anonfun$typed$2(Typer.scala:1765)
	at dotty.tools.dotc.reporting.trace$.op1$2(trace.scala:25)
	at dotty.tools.dotc.reporting.trace$.apply(trace.scala:26)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:1761)
	at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:1822)
	at dotty.tools.dotc.typer.Typer.$anonfun$typedDefDef$1(Typer.scala:1378)
	at dotty.tools.dotc.util.Stats$.track(Stats.scala:35)
	at dotty.tools.dotc.typer.Typer.typedDefDef(Typer.scala:1360)
	at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:1686)
	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:1747)
	at dotty.tools.dotc.typer.Typer.$anonfun$typed$2(Typer.scala:1765)
	at dotty.tools.dotc.reporting.trace$.op1$2(trace.scala:25)
	at dotty.tools.dotc.reporting.trace$.apply(trace.scala:26)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:1761)
	at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:1787)
	at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:1810)
	at dotty.tools.dotc.typer.Typer.$anonfun$typedClassDef$1(Typer.scala:1471)
	at dotty.tools.dotc.util.Stats$.track(Stats.scala:35)
	at dotty.tools.dotc.typer.Typer.typedClassDef(Typer.scala:1401)
	at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:1689)
	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:1747)
	at dotty.tools.dotc.typer.Typer.$anonfun$typed$2(Typer.scala:1765)
	at dotty.tools.dotc.reporting.trace$.op1$2(trace.scala:25)
	at dotty.tools.dotc.reporting.trace$.apply(trace.scala:26)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:1761)
	at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:1787)
	at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:1810)
	at dotty.tools.dotc.typer.Typer.$anonfun$typedClassDef$1(Typer.scala:1471)
	at dotty.tools.dotc.util.Stats$.track(Stats.scala:35)
	at dotty.tools.dotc.typer.Typer.typedClassDef(Typer.scala:1401)
	at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:1689)
	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:1747)
	at dotty.tools.dotc.typer.Typer.$anonfun$typed$2(Typer.scala:1765)
	at dotty.tools.dotc.reporting.trace$.op1$2(trace.scala:25)
	at dotty.tools.dotc.reporting.trace$.apply(trace.scala:26)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:1761)
	at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:1787)
	at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:1810)
	at dotty.tools.dotc.typer.Typer.$anonfun$typedPackageDef$1(Typer.scala:1584)
	at dotty.tools.dotc.util.Stats$.track(Stats.scala:35)
	at dotty.tools.dotc.typer.Typer.typedPackageDef(Typer.scala:1571)
	at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:1729)
	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:1748)
	at dotty.tools.dotc.typer.Typer.$anonfun$typed$2(Typer.scala:1765)
	at dotty.tools.dotc.reporting.trace$.op1$2(trace.scala:25)
	at dotty.tools.dotc.reporting.trace$.apply(trace.scala:26)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:1761)
	at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:1822)
	at dotty.tools.dotc.typer.FrontEnd.$anonfun$typeCheck$1(FrontEnd.scala:66)
	at dotty.tools.dotc.typer.FrontEnd.monitor(FrontEnd.scala:34)
	at dotty.tools.dotc.typer.FrontEnd.typeCheck(FrontEnd.scala:64)
	at dotty.tools.repl.REPLFrontEnd.runOn(ReplFrontEnd.scala:25)
	at dotty.tools.dotc.Run.$anonfun$compileUnits$3(Run.scala:125)
	at scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:12)
	at dotty.tools.dotc.util.Stats$.trackTime(Stats.scala:47)
	at dotty.tools.dotc.Run.$anonfun$compileUnits$2(Run.scala:123)
	at dotty.tools.dotc.Run.$anonfun$compileUnits$2$adapted(Run.scala:121)
	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:191)
	at dotty.tools.dotc.Run.runPhases$1(Run.scala:121)
	at dotty.tools.dotc.Run.$anonfun$compileUnits$1(Run.scala:141)
	at scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:12)
	at dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:88)
	at dotty.tools.dotc.Run.compileUnits(Run.scala:107)
	at dotty.tools.dotc.Run.compileUnits(Run.scala:99)
	at dotty.tools.repl.ReplCompiler.runCompilationUnit(ReplCompiler.scala:188)
	at dotty.tools.repl.ReplCompiler.compile(ReplCompiler.scala:197)
	at dotty.tools.repl.ReplDriver.compile(ReplDriver.scala:223)
	at dotty.tools.repl.ReplDriver.interpret(ReplDriver.scala:196)
	at dotty.tools.repl.ReplDriver.runUntilQuit(ReplDriver.scala:149)
	at dotty.tools.repl.Main$.main(Main.scala:6)
	at dotty.tools.repl.Main.main(Main.scala)

I tried to minimize as much as possible. Replace Int with c.T and the crash remains the same. Giving f an implicit function type doesn't make a difference.
If you replace (c: C) with C the crash goes away.

I would also like to add that I think there's an inconsistency lurking behind this issue. Judging from the stack trace it appears the compiler wants to issue an error message for this code, however the following code compiles without error:

val choose: implicit (c: C) => Set[Int] = implicit c => Set.empty
def applyF(f: C => Set[Int]) = f(new C{type T=Int})
applyF(choose)
odersky added a commit to dotty-staging/dotty that referenced this issue Dec 28, 2017
@odersky
Fix scala#3692: Generalize implicit function subtyping.
e6b4bfa 
With this change,

    (implicit x: C): D  <:  (x: C): D

but not the other way around. This affects subtyping
of dependent implicit function types. Now:

    (implicit x: C) => D  <:  (x: C) => D

See also scala#2000.

As a second change, prevent crashing on type mismatch errors
involving dependent implicit function types.
@odersky odersky mentioned this issue Dec 28, 2017
Closed
odersky added a commit that referenced this issue Jan 13, 2018
@odersky
Merge pull request #3704 from dotty-staging/fix-#3692
f22c662 
Fix #3692: Generalize implicit function subtyping.
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@nicolasstucki @Jasper-M