Dotty: MatchError at GenBCode with class wrapping java style enum

[bishabosha]

Minimized code

class Container : // needs to be wrapped in a class
  enum Color extends java.lang.Enum[Color]:
    case Red, Green, Blue

Output (click arrow to expand)

an unexpected type representation reached the compiler backend while compiling Container.scala: MethodType(List(), List(), TypeRef(ThisType(TypeRef(ThisType(TypeRef(NoPrefix,module class <empty>)),class Container)),class Container$Color)). If possible, please file a bug on https://github.com/lampepfl/dotty/issues
Error while emitting Container.scala
exception occurred while compiling Container.scala
scala.MatchError: MethodType(List(), List(), TypeRef(ThisType(TypeRef(ThisType(TypeRef(NoPrefix,module class <empty>)),class Container)),class Container$Color)) (of class dotty.tools.dotc.core.Types$CachedMethodType) while compiling Container.scala
Exception in thread "main" scala.MatchError: MethodType(List(), List(), TypeRef(ThisType(TypeRef(ThisType(TypeRef(NoPrefix,module class <empty>)),class Container)),class Container$Color)) (of class dotty.tools.dotc.core.Types$CachedMethodType)
    at dotty.tools.backend.jvm.BCodeHelpers.dotty$tools$backend$jvm$BCodeHelpers$$typeToTypeKind(BCodeHelpers.scala:850)
    at dotty.tools.backend.jvm.BCodeHelpers$BCInnerClassGen.toTypeKind(BCodeHelpers.scala:299)
    at dotty.tools.backend.jvm.BCodeHelpers$BCInnerClassGen.toTypeKind$(BCodeHelpers.scala:210)
    at dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.toTypeKind(BCodeSkelBuilder.scala:58)
    at dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.symInfoTK(BCodeSkelBuilder.scala:87)
    at dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.addClassFields$$anonfun$2(BCodeSkelBuilder.scala:268)
    at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:15)
    at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:10)
    at scala.collection.immutable.List.foreach(List.scala:333)
    at dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.addClassFields(BCodeSkelBuilder.scala:274)
    at dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.genPlainClass(BCodeSkelBuilder.scala:134)
    at dotty.tools.backend.jvm.GenBCodePipeline$Worker1.visit(GenBCode.scala:224)
    at dotty.tools.backend.jvm.GenBCodePipeline$Worker1.run(GenBCode.scala:191)
    at dotty.tools.backend.jvm.GenBCodePipeline.buildAndSendToDisk(GenBCode.scala:521)
    at dotty.tools.backend.jvm.GenBCodePipeline.run(GenBCode.scala:487)
    at dotty.tools.backend.jvm.GenBCode.run(GenBCode.scala:57)
    at dotty.tools.dotc.core.Phases$Phase.runOn$$anonfun$1(Phases.scala:295)
    at scala.collection.immutable.List.map(List.scala:246)
    at dotty.tools.dotc.core.Phases$Phase.runOn(Phases.scala:296)
    at dotty.tools.backend.jvm.GenBCode.runOn(GenBCode.scala:61)
    at dotty.tools.dotc.Run.runPhases$4$$anonfun$4(Run.scala:181)
    at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:15)
    at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:10)
    at scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1323)
    at dotty.tools.dotc.Run.runPhases$5(Run.scala:191)
    at dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:199)
    at dotty.runtime.function.JFunction0$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:206)
    at dotty.tools.dotc.Run.compileSources(Run.scala:143)
    at dotty.tools.dotc.Run.compile(Run.scala:125)
    at dotty.tools.dotc.Driver.doCompile(Driver.scala:38)
    at dotty.tools.dotc.Driver.process(Driver.scala:195)
    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:203)
    at dotty.tools.dotc.Main.main(Main.scala)

Notes

with -Ycheck:completeJavaEnums we get the assertion failure: _"non member selection of getter Red in object Color from Container.this.Color.type in Color.this.$outer.Color.Red while compiling Container.scala"_

checking Container.scala after phase MegaPhase{elimErasedValueType, pureStats, vcElideAllocations, arrayApply, elimPolyFunction, tailrec, completeJavaEnums, mixin, lazyVals, memoize, nonLocalReturns, capturedVars}
exception while typing @scala.annotation.static() <static> val Red: (): Container.this.Color = 
  Color.this.$outer.Color.Red of class class dotty.tools.dotc.ast.Trees$ValDef # 2002
exception while typing @scala.annotation.internal.Child[
  (Container.Color.Blue : (): Container.this.Color)
]() @scala.annotation.internal.Child[
  (Container.Color.Green : (): Container.this.Color)
]() @scala.annotation.internal.Child[
  (Container.Color.Red : (): Container.this.Color)
]() sealed abstract class Color($outer: Container, _$name: String, 
  _$ordinal: Int
) extends Enum, Enum {
  super(Color.this._$name, Color.this._$ordinal)
  def productIterator(): scala.collection.Iterator = 
    super[Product].productIterator()
  def productPrefix(): String = super[Product].productPrefix()
  def productElementName(n: Int): String = super[Product].productElementName(n)
  def productElementNames(): scala.collection.Iterator = 
    super[Product].productElementNames()
  private val $outer: Container
  val _$name: String
  val _$ordinal: Int
  @scala.annotation.static() <static> val Red: (): Container.this.Color = 
    Color.this.$outer.Color.Red
  @scala.annotation.static() <static> val Green: (): Container.this.Color = 
    Color.this.$outer.Color.Green
  @scala.annotation.static() <static> val Blue: (): Container.this.Color = 
    Color.this.$outer.Color.Blue
  final def Container$Color$$$outer(): Container = Color.this.$outer
} of class class dotty.tools.dotc.ast.Trees$TypeDef # 2064
exception while typing @scala.annotation.internal.SourceFile("Container.scala") class Container()
   extends
 Object {
  super()
  @scala.annotation.internal.Child[
    (Container.Color.Blue : (): Container.this.Color)
  ]() @scala.annotation.internal.Child[
    (Container.Color.Green : (): Container.this.Color)
  ]() @scala.annotation.internal.Child[
    (Container.Color.Red : (): Container.this.Color)
  ]() sealed abstract class Color($outer: Container, _$name: String, 
    _$ordinal: Int
  ) extends Enum, Enum {
    super(Color.this._$name, Color.this._$ordinal)
    def productIterator(): scala.collection.Iterator = 
      super[Product].productIterator()
    def productPrefix(): String = super[Product].productPrefix()
    def productElementName(n: Int): String = 
      super[Product].productElementName(n)
    def productElementNames(): scala.collection.Iterator = 
      super[Product].productElementNames()
    private val $outer: Container
    val _$name: String
    val _$ordinal: Int
    @scala.annotation.static() <static> val Red: (): Container.this.Color = 
      Color.this.$outer.Color.Red
    @scala.annotation.static() <static> val Green: (): Container.this.Color = 
      Color.this.$outer.Color.Green
    @scala.annotation.static() <static> val Blue: (): Container.this.Color = 
      Color.this.$outer.Color.Blue
    final def Container$Color$$$outer(): Container = Color.this.$outer
  }
  val Color$lzy1: Container.this.Color$ = new Container.this.Color$(this)
  final lazy module def Color(): Container.this.Color$ = this.Color$lzy1
  final module class Color$($outer: Container) extends Object, 
    java.io.Serializable
  , scala.deriving.Mirror.Sum {
    super()
    def values(): Container.this.Color[] = 
      this.$values.values().toArray(
        scala.reflect.ClassTag.apply(classOf[Container.this.Color])
      ).asInstanceOf[Container.this.Color[]]
    private val $values: scala.runtime.EnumValues = 
      new scala.runtime.EnumValues()
    def valueOf($name: String): Container.this.Color = 
      try 
        this.$values.fromName().apply($name).asInstanceOf[Container.this.Color]
       catch 
        {
          case ex$ @ _:java.util.NoSuchElementException => 
            throw new IllegalArgumentException("key not found: ".concat($name))
        }
    private def $new(_$ordinal: Int, $name: String): Container.this.Color = 
      {
        final class $anon($outer: Container.this.Color$) extends 
          Container.this.Color
        , scala.runtime.EnumValue, scala.deriving.Mirror.Singleton {
          super(this.$outer.Container$Color$$$$outer(), $name, _$ordinal)
          override def canEqual(that: Object): Boolean = 
            super[EnumValue].canEqual(that)
          override def productArity(): Int = super[EnumValue].productArity()
          override def productPrefix(): String = 
            super[EnumValue].productPrefix()
          override def productElement(n: Int): Object = 
            super[EnumValue].productElement(n)
          override def productElementName(n: Int): String = 
            super[EnumValue].productElementName(n)
          def fromProduct(p: Product): scala.deriving.Mirror.Singleton = 
            super[Singleton].fromProduct(p)
          def $ordinal(): Int = _$ordinal
          override def toString(): String = $name
          this.$outer.$values.register(this)
          private val $outer: Container.this.Color$
          final def Container$Color$_$$anon$$$outer(): Container.this.Color$ = 
            $outer
          def fromProduct(p: Product): Object = this.fromProduct(p)
        }
        new 
          Container.this.Color with scala.runtime.EnumValue with 
            scala.deriving.Mirror.Singleton
           {...}
        (this):Container.this.Color
      }
    private val Red: Container.this.Color = this.$new(0, "Red")
    case def Red(): Container.this.Color = this.Red
    private val Green: Container.this.Color = this.$new(1, "Green")
    case def Green(): Container.this.Color = this.Green
    private val Blue: Container.this.Color = this.$new(2, "Blue")
    case def Blue(): Container.this.Color = this.Blue
    def ordinal(x$0: Container.this.Color): Int = x$0.ordinal()
    private val $outer: Container
    final def Container$Color$$$$outer(): Container = Container.Color.$outer
    def ordinal(x: Object): Int = 
      this.ordinal(x.asInstanceOf[Container.this.Color])
  }
} of class class dotty.tools.dotc.ast.Trees$TypeDef # 2187
exception while typing package <empty> {
  @scala.annotation.internal.SourceFile("Container.scala") class Container()
     extends
   Object {
    super()
    @scala.annotation.internal.Child[
      (Container.Color.Blue : (): Container.this.Color)
    ]() @scala.annotation.internal.Child[
      (Container.Color.Green : (): Container.this.Color)
    ]() @scala.annotation.internal.Child[
      (Container.Color.Red : (): Container.this.Color)
    ]() sealed abstract class Color($outer: Container, _$name: String, 
      _$ordinal: Int
    ) extends Enum, Enum {
      super(Color.this._$name, Color.this._$ordinal)
      def productIterator(): scala.collection.Iterator = 
        super[Product].productIterator()
      def productPrefix(): String = super[Product].productPrefix()
      def productElementName(n: Int): String = 
        super[Product].productElementName(n)
      def productElementNames(): scala.collection.Iterator = 
        super[Product].productElementNames()
      private val $outer: Container
      val _$name: String
      val _$ordinal: Int
      @scala.annotation.static() <static> val Red: (): Container.this.Color = 
        Color.this.$outer.Color.Red
      @scala.annotation.static() <static> val Green: (): Container.this.Color = 
        Color.this.$outer.Color.Green
      @scala.annotation.static() <static> val Blue: (): Container.this.Color = 
        Color.this.$outer.Color.Blue
      final def Container$Color$$$outer(): Container = Color.this.$outer
    }
    val Color$lzy1: Container.this.Color$ = new Container.this.Color$(this)
    final lazy module def Color(): Container.this.Color$ = this.Color$lzy1
    final module class Color$($outer: Container) extends Object, 
      java.io.Serializable
    , scala.deriving.Mirror.Sum {
      super()
      def values(): Container.this.Color[] = 
        this.$values.values().toArray(
          scala.reflect.ClassTag.apply(classOf[Container.this.Color])
        ).asInstanceOf[Container.this.Color[]]
      private val $values: scala.runtime.EnumValues = 
        new scala.runtime.EnumValues()
      def valueOf($name: String): Container.this.Color = 
        try 
          this.$values.fromName().apply($name).asInstanceOf[Container.this.Color
            ]
         catch 
          {
            case ex$ @ _:java.util.NoSuchElementException => 
              throw 
                new IllegalArgumentException("key not found: ".concat($name))
          }
      private def $new(_$ordinal: Int, $name: String): Container.this.Color = 
        {
          final class $anon($outer: Container.this.Color$) extends 
            Container.this.Color
          , scala.runtime.EnumValue, scala.deriving.Mirror.Singleton {
            super(this.$outer.Container$Color$$$$outer(), $name, _$ordinal)
            override def canEqual(that: Object): Boolean = 
              super[EnumValue].canEqual(that)
            override def productArity(): Int = super[EnumValue].productArity()
            override def productPrefix(): String = 
              super[EnumValue].productPrefix()
            override def productElement(n: Int): Object = 
              super[EnumValue].productElement(n)
            override def productElementName(n: Int): String = 
              super[EnumValue].productElementName(n)
            def fromProduct(p: Product): scala.deriving.Mirror.Singleton = 
              super[Singleton].fromProduct(p)
            def $ordinal(): Int = _$ordinal
            override def toString(): String = $name
            this.$outer.$values.register(this)
            private val $outer: Container.this.Color$
            final def Container$Color$_$$anon$$$outer(): Container.this.Color$
               = 
            $outer
            def fromProduct(p: Product): Object = this.fromProduct(p)
          }
          new 
            Container.this.Color with scala.runtime.EnumValue with 
              scala.deriving.Mirror.Singleton
             {...}
          (this):Container.this.Color
        }
      private val Red: Container.this.Color = this.$new(0, "Red")
      case def Red(): Container.this.Color = this.Red
      private val Green: Container.this.Color = this.$new(1, "Green")
      case def Green(): Container.this.Color = this.Green
      private val Blue: Container.this.Color = this.$new(2, "Blue")
      case def Blue(): Container.this.Color = this.Blue
      def ordinal(x$0: Container.this.Color): Int = x$0.ordinal()
      private val $outer: Container
      final def Container$Color$$$$outer(): Container = Container.Color.$outer
      def ordinal(x: Object): Int = 
        this.ordinal(x.asInstanceOf[Container.this.Color])
    }
  }
} of class class dotty.tools.dotc.ast.Trees$PackageDef # 2188
*** error while checking Container.scala after phase capturedVars ***
exception occurred while compiling Container.scala
java.lang.AssertionError: assertion failed: non member selection of getter Red in object Color from Container.this.Color.type in Color.this.$outer.Color.Red while compiling Container.scala
Exception in thread "main" java.lang.AssertionError: assertion failed: non member selection of getter Red in object Color from Container.this.Color.type in Color.this.$outer.Color.Red
    at dotty.DottyPredef$.assertFail(DottyPredef.scala:17)
    at dotty.tools.dotc.transform.FirstTransform.checkPostCondition(FirstTransform.scala:69)
    at dotty.tools.dotc.transform.TreeChecker.dotty$tools$dotc$transform$TreeChecker$Checker$$_$typedUnadapted$$anonfun$1(TreeChecker.scala:350)
    at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:15)
    at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:10)
    at scala.collection.immutable.List.foreach(List.scala:333)
    at dotty.tools.dotc.transform.TreeChecker$Checker.typedUnadapted(TreeChecker.scala:350)
    at dotty.tools.dotc.typer.Typer.op$1(Typer.scala:2553)
    at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2554)
    at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2557)
    at dotty.tools.dotc.transform.TreeChecker$Checker.typed(TreeChecker.scala:317)
    at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:2671)
    at dotty.tools.dotc.typer.Typer.typedValDef(Typer.scala:1900)
    at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:2397)
    at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2483)
    at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:122)
    at dotty.tools.dotc.transform.TreeChecker$Checker.typedUnadapted(TreeChecker.scala:333)
    at dotty.tools.dotc.typer.Typer.op$1(Typer.scala:2553)
    at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2554)
    at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2557)
    at dotty.tools.dotc.transform.TreeChecker$Checker.typed(TreeChecker.scala:317)
    at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:2579)
    at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:2627)
    at dotty.tools.dotc.transform.TreeChecker$Checker.typedStats(TreeChecker.scala:516)
    at dotty.tools.dotc.typer.Typer.typedClassDef(Typer.scala:2081)
    at dotty.tools.dotc.transform.TreeChecker$Checker.typedClassDef(TreeChecker.scala:448)
    at dotty.tools.dotc.typer.Typer.typedTypeOrClassDef$2(Typer.scala:2411)
    at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:2415)
    at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2483)
    at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:122)
    at dotty.tools.dotc.transform.TreeChecker$Checker.typedUnadapted(TreeChecker.scala:333)
    at dotty.tools.dotc.typer.Typer.op$1(Typer.scala:2553)
    at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2554)
    at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2557)
    at dotty.tools.dotc.transform.TreeChecker$Checker.typed(TreeChecker.scala:317)
    at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:2579)
    at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:2627)
    at dotty.tools.dotc.transform.TreeChecker$Checker.typedStats(TreeChecker.scala:516)
    at dotty.tools.dotc.typer.Typer.typedClassDef(Typer.scala:2081)
    at dotty.tools.dotc.transform.TreeChecker$Checker.typedClassDef(TreeChecker.scala:448)
    at dotty.tools.dotc.typer.Typer.typedTypeOrClassDef$2(Typer.scala:2411)
    at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:2415)
    at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2483)
    at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:122)
    at dotty.tools.dotc.transform.TreeChecker$Checker.typedUnadapted(TreeChecker.scala:333)
    at dotty.tools.dotc.typer.Typer.op$1(Typer.scala:2553)
    at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2554)
    at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2557)
    at dotty.tools.dotc.transform.TreeChecker$Checker.typed(TreeChecker.scala:317)
    at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:2579)
    at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:2627)
    at dotty.tools.dotc.transform.TreeChecker$Checker.typedStats(TreeChecker.scala:516)
    at dotty.tools.dotc.typer.Typer.typedPackageDef(Typer.scala:2207)
    at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:2455)
    at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2484)
    at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:122)
    at dotty.tools.dotc.transform.TreeChecker$Checker.typedUnadapted(TreeChecker.scala:333)
    at dotty.tools.dotc.typer.Typer.op$1(Typer.scala:2553)
    at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2554)
    at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2557)
    at dotty.tools.dotc.transform.TreeChecker$Checker.typed(TreeChecker.scala:317)
    at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:2671)
    at dotty.tools.dotc.transform.TreeChecker.check(TreeChecker.scala:151)
    at dotty.tools.dotc.transform.TreeChecker.run(TreeChecker.scala:120)
    at dotty.tools.dotc.core.Phases$Phase.runOn$$anonfun$1(Phases.scala:295)
    at scala.collection.immutable.List.map(List.scala:246)
    at dotty.tools.dotc.core.Phases$Phase.runOn(Phases.scala:296)
    at dotty.tools.dotc.Run.runPhases$4$$anonfun$4(Run.scala:181)
    at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:15)
    at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:10)
    at scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1323)
    at dotty.tools.dotc.Run.runPhases$5(Run.scala:191)
    at dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:199)
    at dotty.runtime.function.JFunction0$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:206)
    at dotty.tools.dotc.Run.compileSources(Run.scala:143)
    at dotty.tools.dotc.Run.compile(Run.scala:125)
    at dotty.tools.dotc.Driver.doCompile(Driver.scala:38)
    at dotty.tools.dotc.Driver.process(Driver.scala:195)
    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:203)
    at dotty.tools.dotc.Main.main(Main.scala)

[bishabosha]

This should probably not be allowed as in JLS enums are always static classes