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The Scala 3 compiler, also known as Dotty.
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java.lang.AssertionError: assertion failed #20397

Closed Bersier closed 2 weeks ago

Bersier commented 4 months ago

Compiler version

3.4.1

Minimized code

trait Env2[+V]:
  type Shape <: TList[V]
  def extended(value: V): Env2[V]{ type Shape = Scope.Extended[V, Shape] }

object Scope:
  type Extended[V, L <: TList[V]] <: Nothing = L match
    case Empty.type => Nothing

trait TList[E]
case object Empty extends TList[Nothing]

Start of compiler crash error

java.lang.AssertionError: assertion failed
    at scala.runtime.Scala3RunTime$.assertFailed(Scala3RunTime.scala:11)
    at dotty.tools.dotc.core.Types$LazyRef.ref(Types.scala:3186)
    at dotty.tools.dotc.core.Types$LazyRef.tryNormalize(Types.scala:3179)
    at dotty.tools.dotc.core.Types$Type.normalized(Types.scala:1522)
Gedochao commented 4 months ago

full crash output on 3.4.1 (it's the same on 3.4.2-RC1)

assertion failure for Scope.Extended[V, ...] <:< TList[V], frozen = true

  exception occurred while typechecking /Users/pchabelski/IdeaProjects/scala-cli-tests/compiler-repro/repro.scala

  An unhandled exception was thrown in the compiler.
  Please file a crash report here:
  https://github.com/scala/scala3/issues/new/choose
  For non-enriched exceptions, compile with -Yno-enrich-error-messages.

     while compiling: /Users/pchabelski/IdeaProjects/scala-cli-tests/compiler-repro/repro.scala
        during phase: typer
                mode: Mode(ImplicitsEnabled)
     library version: version 2.13.12
    compiler version: version 3.4.1
            settings: -classpath /Users/pchabelski/Library/Caches/Coursier/v1/https/repo1.maven.org/maven2/org/scala-lang/scala3-library_3/3.4.1/scala3-library_3-3.4.1.jar:/Users/pchabelski/Library/Caches/Coursier/v1/https/repo1.maven.org/maven2/org/scala-lang/scala-library/2.13.12/scala-library-2.13.12.jar -d /Users/pchabelski/IdeaProjects/scala-cli-tests/compiler-repro/.scala-build/compiler-repro_a5fa0afddc-28ebf8438e/classes/main -java-output-version 17 -sourceroot /Users/pchabelski/IdeaProjects/scala-cli-tests/compiler-repro

Exception in thread "main" java.lang.AssertionError: assertion failed
        at scala.runtime.Scala3RunTime$.assertFailed(Scala3RunTime.scala:11)
        at dotty.tools.dotc.core.Types$LazyRef.ref(Types.scala:3186)
        at dotty.tools.dotc.core.Types$LazyRef.tryNormalize(Types.scala:3179)
        at dotty.tools.dotc.core.Types$Type.normalized(Types.scala:1522)
        at dotty.tools.dotc.core.Types$.dotty$tools$dotc$core$Types$AppliedType$$_$tryMatchAlias$1$$anonfun$1$$anonfun$1(Types.scala:4570)
        at scala.collection.immutable.List.map(List.scala:250)
        at dotty.tools.dotc.core.Types$AppliedType.tryMatchAlias$1$$anonfun$1(Types.scala:4570)
        at dotty.tools.dotc.core.MatchTypeTrace$.recurseWith(MatchTypeTrace.scala:81)
        at dotty.tools.dotc.core.Types$AppliedType.tryMatchAlias$1(Types.scala:4571)
        at dotty.tools.dotc.core.Types$AppliedType.tryNormalize(Types.scala:4576)
        at dotty.tools.dotc.core.SymDenotations$ClassDenotation.recur$4(SymDenotations.scala:2218)
        at dotty.tools.dotc.core.SymDenotations$ClassDenotation.baseTypeOf(SymDenotations.scala:2338)
        at dotty.tools.dotc.core.Types$Type.baseType(Types.scala:1194)
        at dotty.tools.dotc.core.TypeComparer.nonExprBaseType(TypeComparer.scala:1571)
        at dotty.tools.dotc.core.TypeComparer.tryBaseType$1(TypeComparer.scala:896)
        at dotty.tools.dotc.core.TypeComparer.compareAppliedType2$1(TypeComparer.scala:1410)
        at dotty.tools.dotc.core.TypeComparer.thirdTry$1(TypeComparer.scala:625)
        at dotty.tools.dotc.core.TypeComparer.secondTry$1(TypeComparer.scala:552)
        at dotty.tools.dotc.core.TypeComparer.firstTry$1(TypeComparer.scala:416)
        at dotty.tools.dotc.core.TypeComparer.recur(TypeComparer.scala:1553)
        at dotty.tools.dotc.core.TypeComparer.isSubType(TypeComparer.scala:214)
        at dotty.tools.dotc.core.TypeComparer.isSubType(TypeComparer.scala:224)
        at dotty.tools.dotc.core.TypeComparer.isSub(TypeComparer.scala:226)
        at dotty.tools.dotc.core.ConstraintHandling.op$proxy3$1(ConstraintHandling.scala:471)
        at dotty.tools.dotc.core.ConstraintHandling.isSubTypeWhenFrozen(ConstraintHandling.scala:471)
        at dotty.tools.dotc.core.ConstraintHandling.isSubTypeWhenFrozen$(ConstraintHandling.scala:29)
        at dotty.tools.dotc.core.TypeComparer.isSubTypeWhenFrozen(TypeComparer.scala:30)
        at dotty.tools.dotc.core.TypeComparer$.isSubTypeWhenFrozen(TypeComparer.scala:3149)
        at dotty.tools.dotc.core.Types$Type.frozen_$less$colon$less(Types.scala:1104)
        at dotty.tools.dotc.core.Types$TypeBounds.$amp(Types.scala:5484)
        at dotty.tools.dotc.core.Types$TypeBounds.$amp(Types.scala:5494)
        at dotty.tools.dotc.core.Types$Type.recoverable_$amp(Types.scala:1225)
        at dotty.tools.dotc.core.Types$Type.goRefined$1(Types.scala:837)
        at dotty.tools.dotc.core.Types$Type.go$1(Types.scala:774)
        at dotty.tools.dotc.core.Types$Type.goRec$1(Types.scala:818)
        at dotty.tools.dotc.core.Types$Type.go$1(Types.scala:776)
        at dotty.tools.dotc.core.Types$Type.findMember(Types.scala:936)
        at dotty.tools.dotc.core.Types$Type.memberBasedOnFlags(Types.scala:728)
        at dotty.tools.dotc.core.Types$Type.nonPrivateMember(Types.scala:718)
        at dotty.tools.dotc.core.Types$NamedType.memberDenot(Types.scala:2516)
        at dotty.tools.dotc.core.Types$NamedType.reload$1(Types.scala:2849)
        at dotty.tools.dotc.core.Types$NamedType.withPrefix(Types.scala:2864)
        at dotty.tools.dotc.core.Types$NamedType.derivedSelect(Types.scala:2797)
        at dotty.tools.dotc.core.Substituters$.substThis(Substituters.scala:114)
        at dotty.tools.dotc.core.Substituters$SubstThisMap.apply(Substituters.scala:189)
        at dotty.tools.dotc.core.Types$TypeMap.mapOver$$anonfun$1(Types.scala:6133)
        at dotty.tools.dotc.core.Types$LazyRef.ref(Types.scala:3192)
        at dotty.tools.dotc.core.Types$RecType$$anon$3.apply(Types.scala:3343)
        at dotty.tools.dotc.core.Types$RecType$$anon$3.apply(Types.scala:3339)
        at dotty.tools.dotc.core.Types$TypeAccumulator.op$proxy27$1(Types.scala:6548)
        at dotty.tools.dotc.core.Types$TypeAccumulator.foldArgs$3(Types.scala:6548)
        at dotty.tools.dotc.core.Types$TypeAccumulator.foldOver(Types.scala:6552)
        at dotty.tools.dotc.core.Types$RecType$$anon$3.apply(Types.scala:3344)
        at dotty.tools.dotc.core.Types$RecType$$anon$3.apply(Types.scala:3339)
        at dotty.tools.dotc.core.Types$TypeAccumulator.op$proxy28$1(Types.scala:6574)
        at dotty.tools.dotc.core.Types$TypeAccumulator.foldOver(Types.scala:6574)
        at dotty.tools.dotc.core.Types$RecType$$anon$3.apply(Types.scala:3344)
        at dotty.tools.dotc.core.Types$RecType$$anon$3.apply(Types.scala:3339)
        at dotty.tools.dotc.core.Types$TypeAccumulator.foldOver(Types.scala:6603)
        at dotty.tools.dotc.core.Types$RecType$$anon$3.apply(Types.scala:3344)
        at dotty.tools.dotc.core.Types$RecType$$anon$3.apply(Types.scala:3339)
        at dotty.tools.dotc.core.Types$RecType.isReferredToBy(Types.scala:3348)
        at dotty.tools.dotc.core.Types$RecType$.closeOver(Types.scala:3405)
        at dotty.tools.dotc.typer.TypeAssigner.assignType(TypeAssigner.scala:486)
        at dotty.tools.dotc.typer.TypeAssigner.assignType$(TypeAssigner.scala:16)
        at dotty.tools.dotc.typer.Typer.assignType(Typer.scala:120)
        at dotty.tools.dotc.typer.Typer.typedRefinedTypeTree(Typer.scala:2214)
        at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3139)
        at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3197)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3274)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3278)
        at dotty.tools.dotc.typer.Typer.typedType(Typer.scala:3392)
        at dotty.tools.dotc.typer.Namer.typedAheadType$$anonfun$1(Namer.scala:1682)
        at dotty.tools.dotc.typer.Namer.typedAhead(Namer.scala:1675)
        at dotty.tools.dotc.typer.Namer.typedAheadType(Namer.scala:1682)
        at dotty.tools.dotc.typer.Namer.valOrDefDefSig(Namer.scala:1777)
        at dotty.tools.dotc.typer.Namer.defDefSig(Namer.scala:1828)
        at dotty.tools.dotc.typer.Namer$Completer.typeSig(Namer.scala:808)
        at dotty.tools.dotc.typer.Namer$Completer.completeInCreationContext(Namer.scala:955)
        at dotty.tools.dotc.typer.Namer$Completer.complete(Namer.scala:831)
        at dotty.tools.dotc.core.SymDenotations$SymDenotation.completeFrom(SymDenotations.scala:178)
        at dotty.tools.dotc.core.Denotations$Denotation.completeInfo$1(Denotations.scala:190)
        at dotty.tools.dotc.core.Denotations$Denotation.info(Denotations.scala:192)
        at dotty.tools.dotc.core.SymDenotations$SymDenotation.ensureCompleted(SymDenotations.scala:398)
        at dotty.tools.dotc.typer.Typer.retrieveSym(Typer.scala:3060)
        at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:3085)
        at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3196)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3274)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3278)
        at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:3300)
        at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:3346)
        at dotty.tools.dotc.typer.Typer.typedClassDef(Typer.scala:2790)
        at dotty.tools.dotc.typer.Typer.typedTypeOrClassDef$1(Typer.scala:3101)
        at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:3105)
        at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3196)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3274)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3278)
        at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:3300)
        at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:3346)
        at dotty.tools.dotc.typer.Typer.typedPackageDef(Typer.scala:2923)
        at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3147)
        at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3197)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3274)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3278)
        at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:3389)
        at dotty.tools.dotc.typer.TyperPhase.typeCheck$$anonfun$1(TyperPhase.scala:47)
        at scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
        at scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
        at dotty.tools.dotc.core.Phases$Phase.monitor(Phases.scala:477)
        at dotty.tools.dotc.typer.TyperPhase.typeCheck(TyperPhase.scala:53)
        at dotty.tools.dotc.typer.TyperPhase.$anonfun$4(TyperPhase.scala:99)
        at scala.collection.Iterator$$anon$6.hasNext(Iterator.scala:479)
        at scala.collection.Iterator$$anon$9.hasNext(Iterator.scala:583)
        at scala.collection.immutable.List.prependedAll(List.scala:152)
        at scala.collection.immutable.List$.from(List.scala:684)
        at scala.collection.immutable.List$.from(List.scala:681)
        at scala.collection.IterableOps$WithFilter.map(Iterable.scala:898)
        at dotty.tools.dotc.typer.TyperPhase.runOn(TyperPhase.scala:100)
        at dotty.tools.dotc.Run.runPhases$1$$anonfun$1(Run.scala:315)
        at scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
        at scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
        at scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1323)
        at dotty.tools.dotc.Run.runPhases$1(Run.scala:337)
        at dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:350)
        at dotty.tools.dotc.Run.compileUnits$$anonfun$adapted$1(Run.scala:360)
        at dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:69)
        at dotty.tools.dotc.Run.compileUnits(Run.scala:360)
        at dotty.tools.dotc.Run.compileSources(Run.scala:261)
        at dotty.tools.dotc.Run.compile(Run.scala:246)
        at dotty.tools.dotc.Driver.doCompile(Driver.scala:37)
        at dotty.tools.dotc.Driver.process(Driver.scala:196)
        at dotty.tools.dotc.Driver.process(Driver.scala:164)
        at dotty.tools.dotc.Driver.process(Driver.scala:176)
        at dotty.tools.dotc.Driver.main(Driver.scala:206)
        at dotty.tools.dotc.Main.main(Main.scala)

This seems to be fixed to a proper error on the current nightly

-- [E140] Cyclic Error: /Users/pchabelski/IdeaProjects/scala-cli-tests/compiler-repro/repro.scala:3:40 
3 |  def extended(value: V): Env2[V]{ type Shape = Scope.Extended[V, Shape] }
  |                                        ^
  |illegal cyclic type reference: alias Scope.Extended[V, <refinement>.this.Shape] of ... (caught cyclic reference) ... refers back to the type itself
  |
  | Run with -explain-cyclic for more details.
-- Warning: /Users/pchabelski/IdeaProjects/scala-cli-tests/compiler-repro/repro.scala:3:66 
3 |  def extended(value: V): Env2[V]{ type Shape = Scope.Extended[V, Shape] }
  |                                                                  ^^^^^
  |                             forward reference in refinement is deprecated
1 warning found
1 error found
Bersier commented 2 weeks ago

This crash still happens in the LTS (Scala 3.3.5-RC1-bin-20240808-53791b0-NIGHTLY). It should thus be reopened.

odersky commented 2 weeks ago

This tracker is for the current version, not LTS. LTS backports fixes on a reasonable effort basis.

Bersier commented 2 weeks ago

@odersky I see. Should I open another issue about this for the LTS? Or should all issues that only affect the LTS be closed?

While I personally don't care about the LTS, I do think that any valid unresolved issue applying to current releases should remain open, even if it never gets fixed. It shows the world that this issue is acknowledged, rather than dismissed. Closing an issue implies resolution (aka closure). Also, closing an issue that is unresolved basically "loses" it in a sea of other closed issues, most of which are actually resolved, and all of which get filtered out by GitHub by default.

sjrd commented 2 weeks ago

Here, closing an issue means that it is resolved in the main branch. Not all repos apply the same policies.

Bersier commented 2 weeks ago

@sjrd Alright. I'm not sure about the point of such an "LTS", but since I don't use it, I won't press the issue further.

I'll close #19752. #20263 should also be considered for closure, as it is resolved in the main branch.