Bad owner of anonymous function after expandSAMs

[jrlemieux]

Compiler version

3.6.4

Minimized code

object Bug:

  def m0(f: PartialFunction[Char, Unit]): Unit = ()

  def m1(): Unit =
    m0: x =>
      "abc".filter(_ == x) match
        case _ => ()

Output (click arrow to expand)

See bug.log (or the more readable bug-nocolor.log) in attached zip file.

files.zip

[jrlemieux]

Compiles without crash if m0 delcared as

  def m0(f: Char => Unit): Unit = ()

Also compiles without crash with this variation (m0 receives a function rather than a partial function, but there is no "match"):

  def m0(f: PartialFunction[Char, Unit]): Unit = ()

  def m1(): Unit =
    m0: x =>
      "abc".filter(_ == x)

And this variation also works (m0 receives a partial function):

  def m0(f: PartialFunction[Char, Unit]): Unit = ()

  def m1(): Unit =
    m0:
      case x =>
        "abc".filter(_ == x) match
          case _ => ()

[som-snytt]

Relatedly #23002 does not help.

[KacperFKorban]

This is more likely a firstTransform/expandSAMs, since it fails with -Ycheck:all with:

checking wiadro/i23054.scala after phase MegaPhase{crossVersionChecks, firstTransform, checkReentrant, elimPackagePrefixes, cookComments, checkLoopingImplicits, betaReduce, inlineVals, expandSAMs, elimRepeated, refchecks, dropForMap}
*** error while checking wiadro/i23054.scala after phase MegaPhase{crossVersionChecks, firstTransform, checkReentrant, elimPackagePrefixes, cookComments, checkLoopingImplicits, betaReduce, inlineVals, expandSAMs, elimRepeated, refchecks, dropForMap} ***

  unhandled exception while running Ycheck on wiadro/i23054.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 -Xno-enrich-error-messages.


     while compiling: wiadro/i23054.scala
        during phase: Ycheck
                mode: Mode(ImplicitsEnabled)
     library version: version 2.13.16
    compiler version: version 3.7.1-RC1-bin-20250430-c4531d4-NIGHTLY-git-c4531d4
            settings: -Vprint List(all) -Ycheck List(all) -classpath .cache/coursier/v1/https/repo1.maven.org/maven2/org/scala-lang/scala3-library_3/3.7.1-RC1-bin-20250430-c4531d4-NIGHTLY/scala3-library_3-3.7.1-RC1-bin-20250430-c4531d4-NIGHTLY.jar:.cache/coursier/v1/https/repo1.maven.org/maven2/org/scala-lang/scala-library/2.13.16/scala-library-2.13.16.jar -d wiadro/.scala-build/wiadro_5da420ddc5-c24cb85a9c/classes/main -sourceroot wiadro

Exception in thread "main" java.lang.AssertionError: assertion failed: bad owner; method $anonfun has owner method $anonfun, expected was method isDefinedAt
owner chain = method $anonfun, method $anonfun, method m1, object Bug, package <empty>, package <root>, ctxOwners = method isDefinedAt, method isDefinedAt, method isDefinedAt, method isDefinedAt, anonymous class scala.runtime.AbstractPartialFunction[Char, Unit] with 
  Serializable {...}, anonymous class scala.runtime.AbstractPartialFunction[Char, Unit] with 
  Serializable {...}, method m1, method m1, method m1, method m1, object Bug, object Bug, package <empty>, package <root>, package <root>, package <root>, package <root>, package <root>, package <root>, package <root>,  <none>,  <none>,  <none>,  <none>
	at scala.runtime.Scala3RunTime$.assertFailed(Scala3RunTime.scala:8)
	at dotty.tools.dotc.transform.TreeChecker$Checker.checkOwner(TreeChecker.scala:575)
	at dotty.tools.dotc.transform.TreeChecker$Checker.typedStats$$anonfun$1(TreeChecker.scala:687)
	at scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
	at scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
	at scala.collection.immutable.List.foreach(List.scala:334)
	at dotty.tools.dotc.transform.TreeChecker$Checker.typedStats(TreeChecker.scala:686)
	at dotty.tools.dotc.typer.Typer.typedBlockStats(Typer.scala:1486)
	at dotty.tools.dotc.typer.Typer.typedBlock(Typer.scala:1490)
	at dotty.tools.dotc.transform.TreeChecker$Checker.typedBlock$$anonfun$1$$anonfun$1(TreeChecker.scala:673)
	at dotty.tools.dotc.transform.TreeChecker$Checker.withDefinedSyms(TreeChecker.scala:278)
	at dotty.tools.dotc.transform.TreeChecker$Checker.typedBlock$$anonfun$1(TreeChecker.scala:673)
	at dotty.tools.dotc.transform.TreeChecker$Checker.withBlock(TreeChecker.scala:306)
	at dotty.tools.dotc.transform.TreeChecker$Checker.typedBlock(TreeChecker.scala:673)
	at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3570)
	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3650)
	at dotty.tools.dotc.transform.TreeChecker$Checker.typedUnadapted(TreeChecker.scala:434)
	at dotty.tools.dotc.typer.ProtoTypes$FunProto.$anonfun$7(ProtoTypes.scala:536)
	at dotty.tools.dotc.typer.ProtoTypes$FunProto.cacheTypedArg(ProtoTypes.scala:459)
	at dotty.tools.dotc.typer.ProtoTypes$FunProto.typedArg(ProtoTypes.scala:537)
	at dotty.tools.dotc.typer.Applications$ApplyToUntyped.typedArg(Applications.scala:1047)
	at dotty.tools.dotc.typer.Applications$ApplyToUntyped.typedArg(Applications.scala:1047)
	at dotty.tools.dotc.typer.Applications$Application.addTyped$1(Applications.scala:727)
	at dotty.tools.dotc.typer.Applications$Application.matchArgs(Applications.scala:796)
	at dotty.tools.dotc.typer.Applications$Application.init(Applications.scala:606)
	at dotty.tools.dotc.typer.Applications$TypedApply.<init>(Applications.scala:922)
	at dotty.tools.dotc.typer.Applications$ApplyToUntyped.<init>(Applications.scala:1046)
	at dotty.tools.dotc.typer.Applications.ApplyTo(Applications.scala:1314)
	at dotty.tools.dotc.typer.Applications.ApplyTo$(Applications.scala:466)
	at dotty.tools.dotc.typer.Typer.ApplyTo(Typer.scala:154)
	at dotty.tools.dotc.typer.Applications.simpleApply$1(Applications.scala:1119)
	at dotty.tools.dotc.typer.Applications.$anonfun$15(Applications.scala:1228)
	at dotty.tools.dotc.typer.Typer$.tryEither(Typer.scala:127)
	at dotty.tools.dotc.typer.Applications.realApply$1(Applications.scala:1243)
	at dotty.tools.dotc.typer.Applications.typedApply(Applications.scala:1288)
	at dotty.tools.dotc.typer.Applications.typedApply$(Applications.scala:466)
	at dotty.tools.dotc.transform.TreeChecker$Checker.typedApply(TreeChecker.scala:543)
	at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3562)
	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3650)
	at dotty.tools.dotc.transform.TreeChecker$Checker.typedUnadapted(TreeChecker.scala:434)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3727)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3732)
	at dotty.tools.dotc.transform.TreeChecker$Checker.typed(TreeChecker.scala:416)
	at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:3843)
	at dotty.tools.dotc.typer.Typer.typedMatch(Typer.scala:2080)
	at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3577)
	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3650)
	at dotty.tools.dotc.transform.TreeChecker$Checker.typedUnadapted(TreeChecker.scala:434)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3727)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3732)
	at dotty.tools.dotc.transform.TreeChecker$Checker.typed(TreeChecker.scala:416)
	at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:3843)
	at dotty.tools.dotc.typer.Typer.$anonfun$66(Typer.scala:2954)
	at dotty.tools.dotc.inlines.PrepareInlineable$.dropInlineIfError(PrepareInlineable.scala:256)
	at dotty.tools.dotc.typer.Typer.typedDefDef(Typer.scala:2954)
	at dotty.tools.dotc.transform.TreeChecker$Checker.typedDefDef$$anonfun$1(TreeChecker.scala:648)
	at dotty.tools.dotc.transform.TreeChecker$Checker.withDefinedSyms(TreeChecker.scala:278)
	at dotty.tools.dotc.transform.TreeChecker$Checker.typedDefDef(TreeChecker.scala:651)
	at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:3544)
	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3649)
	at dotty.tools.dotc.transform.TreeChecker$Checker.typedUnadapted(TreeChecker.scala:434)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3727)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3732)
	at dotty.tools.dotc.transform.TreeChecker$Checker.typed(TreeChecker.scala:416)
	at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:3754)
	at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:3800)
	at dotty.tools.dotc.transform.TreeChecker$Checker.typedStats(TreeChecker.scala:691)
	at dotty.tools.dotc.typer.Typer.typedClassDef(Typer.scala:3222)
	at dotty.tools.dotc.transform.TreeChecker$Checker.typedClassDef(TreeChecker.scala:618)
	at dotty.tools.dotc.typer.Typer.typedTypeOrClassDef$1(Typer.scala:3550)
	at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:3554)
	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3649)
	at dotty.tools.dotc.transform.TreeChecker$Checker.typedUnadapted(TreeChecker.scala:434)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3727)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3732)
	at dotty.tools.dotc.transform.TreeChecker$Checker.typed(TreeChecker.scala:416)
	at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:3754)
	at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:3800)
	at dotty.tools.dotc.transform.TreeChecker$Checker.typedStats(TreeChecker.scala:691)
	at dotty.tools.dotc.typer.Typer.typedBlockStats(Typer.scala:1486)
	at dotty.tools.dotc.typer.Typer.typedBlock(Typer.scala:1490)
	at dotty.tools.dotc.transform.TreeChecker$Checker.typedBlock$$anonfun$1$$anonfun$1(TreeChecker.scala:673)
	at dotty.tools.dotc.transform.TreeChecker$Checker.withDefinedSyms(TreeChecker.scala:278)
	at dotty.tools.dotc.transform.TreeChecker$Checker.typedBlock$$anonfun$1(TreeChecker.scala:673)
	at dotty.tools.dotc.transform.TreeChecker$Checker.withBlock(TreeChecker.scala:306)
	at dotty.tools.dotc.transform.TreeChecker$Checker.typedBlock(TreeChecker.scala:673)
	at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3570)
	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3650)
	at dotty.tools.dotc.transform.TreeChecker$Checker.typedUnadapted(TreeChecker.scala:434)
	at dotty.tools.dotc.typer.ProtoTypes$FunProto.$anonfun$7(ProtoTypes.scala:536)
	at dotty.tools.dotc.typer.ProtoTypes$FunProto.cacheTypedArg(ProtoTypes.scala:459)
	at dotty.tools.dotc.typer.ProtoTypes$FunProto.typedArg(ProtoTypes.scala:537)
	at dotty.tools.dotc.typer.Applications$ApplyToUntyped.typedArg(Applications.scala:1047)
	at dotty.tools.dotc.typer.Applications$ApplyToUntyped.typedArg(Applications.scala:1047)
	at dotty.tools.dotc.typer.Applications$Application.addTyped$1(Applications.scala:727)
	at dotty.tools.dotc.typer.Applications$Application.matchArgs(Applications.scala:796)
	at dotty.tools.dotc.typer.Applications$Application.init(Applications.scala:606)
	at dotty.tools.dotc.typer.Applications$TypedApply.<init>(Applications.scala:922)
	at dotty.tools.dotc.typer.Applications$ApplyToUntyped.<init>(Applications.scala:1046)
	at dotty.tools.dotc.typer.Applications.ApplyTo(Applications.scala:1314)
	at dotty.tools.dotc.typer.Applications.ApplyTo$(Applications.scala:466)
	at dotty.tools.dotc.typer.Typer.ApplyTo(Typer.scala:154)
	at dotty.tools.dotc.typer.Applications.simpleApply$1(Applications.scala:1119)
	at dotty.tools.dotc.typer.Applications.$anonfun$15(Applications.scala:1228)
	at dotty.tools.dotc.typer.Typer$.tryEither(Typer.scala:127)
	at dotty.tools.dotc.typer.Applications.realApply$1(Applications.scala:1243)
	at dotty.tools.dotc.typer.Applications.typedApply(Applications.scala:1288)
	at dotty.tools.dotc.typer.Applications.typedApply$(Applications.scala:466)
	at dotty.tools.dotc.transform.TreeChecker$Checker.typedApply(TreeChecker.scala:543)
	at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3562)
	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3650)
	at dotty.tools.dotc.transform.TreeChecker$Checker.typedUnadapted(TreeChecker.scala:434)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3727)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3732)
	at dotty.tools.dotc.transform.TreeChecker$Checker.typed(TreeChecker.scala:416)
	at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:3843)
	at dotty.tools.dotc.typer.Typer.$anonfun$66(Typer.scala:2954)
	at dotty.tools.dotc.inlines.PrepareInlineable$.dropInlineIfError(PrepareInlineable.scala:256)
	at dotty.tools.dotc.typer.Typer.typedDefDef(Typer.scala:2954)
	at dotty.tools.dotc.transform.TreeChecker$Checker.typedDefDef$$anonfun$1(TreeChecker.scala:648)
	at dotty.tools.dotc.transform.TreeChecker$Checker.withDefinedSyms(TreeChecker.scala:278)
	at dotty.tools.dotc.transform.TreeChecker$Checker.typedDefDef(TreeChecker.scala:651)
	at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:3544)
	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3649)
	at dotty.tools.dotc.transform.TreeChecker$Checker.typedUnadapted(TreeChecker.scala:434)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3727)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3732)
	at dotty.tools.dotc.transform.TreeChecker$Checker.typed(TreeChecker.scala:416)
	at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:3754)
	at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:3800)
	at dotty.tools.dotc.transform.TreeChecker$Checker.typedStats(TreeChecker.scala:691)
	at dotty.tools.dotc.typer.Typer.typedClassDef(Typer.scala:3222)
	at dotty.tools.dotc.transform.TreeChecker$Checker.typedClassDef(TreeChecker.scala:618)
	at dotty.tools.dotc.typer.Typer.typedTypeOrClassDef$1(Typer.scala:3550)
	at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:3554)
	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3649)
	at dotty.tools.dotc.transform.TreeChecker$Checker.typedUnadapted(TreeChecker.scala:434)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3727)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3732)
	at dotty.tools.dotc.transform.TreeChecker$Checker.typed(TreeChecker.scala:416)
	at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:3754)
	at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:3800)
	at dotty.tools.dotc.transform.TreeChecker$Checker.typedStats(TreeChecker.scala:691)
	at dotty.tools.dotc.typer.Typer.typedPackageDef(Typer.scala:3355)
	at dotty.tools.dotc.transform.TreeChecker$Checker.typedPackageDef(TreeChecker.scala:717)
	at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3596)
	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3650)
	at dotty.tools.dotc.transform.TreeChecker$Checker.typedUnadapted(TreeChecker.scala:434)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3727)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3732)
	at dotty.tools.dotc.transform.TreeChecker$Checker.typed(TreeChecker.scala:416)
	at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:3843)
	at dotty.tools.dotc.transform.TreeChecker.check(TreeChecker.scala:131)
	at dotty.tools.dotc.transform.TreeChecker.run(TreeChecker.scala:111)
	at dotty.tools.dotc.core.Phases$Phase.runOn$$anonfun$1(Phases.scala:383)
	at scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
	at scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
	at scala.collection.immutable.List.foreach(List.scala:334)
	at dotty.tools.dotc.core.Phases$Phase.runOn(Phases.scala:376)
	at dotty.tools.dotc.Run.runPhases$1$$anonfun$1(Run.scala:368)
	at scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
	at scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
	at scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1324)
	at dotty.tools.dotc.Run.runPhases$1(Run.scala:361)
	at dotty.tools.dotc.Run.compileUnits$$anonfun$1$$anonfun$2(Run.scala:408)
	at dotty.tools.dotc.Run.compileUnits$$anonfun$1$$anonfun$adapted$1(Run.scala:408)
	at scala.Function0.apply$mcV$sp(Function0.scala:42)
	at dotty.tools.dotc.Run.showProgress(Run.scala:470)
	at dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:408)
	at dotty.tools.dotc.Run.compileUnits$$anonfun$adapted$1(Run.scala:420)
	at dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:69)
	at dotty.tools.dotc.Run.compileUnits(Run.scala:420)
	at dotty.tools.dotc.Run.compileSources(Run.scala:307)
	at dotty.tools.dotc.Run.compile(Run.scala:292)
	at dotty.tools.dotc.Driver.doCompile(Driver.scala:37)
	at dotty.tools.dotc.Driver.process(Driver.scala:201)
	at dotty.tools.dotc.Driver.process(Driver.scala:169)
	at dotty.tools.dotc.Driver.process(Driver.scala:181)
	at dotty.tools.dotc.Driver.main(Driver.scala:211)
	at dotty.tools.dotc.Main.main(Main.scala)

[som-snytt]

ExpandSAMs copies the Match but doesn't change owner the selector expression containing the anonfun (the filter). I took a look the other day but didn't get back to it. This is the dubious support of anything more than x for the selector for synthesizing the partial function. It might be an easy fix for someone or a learning exercise for someone else (as I already learned).

[som-snytt]

Noticed innocently (not maliciously) on the forum.

def pf: PartialFunction[List[Int], Option[(Int, List[Int])]] =
    _.span(_ % 2 == 0) match
    case (Nil, x :: xs) => Some(x, xs)
    case (Nil, _)       => None
    case (evens, xs)    => Some(evens.sum, xs)

@main def test = println:
  pf:
    List(2,4,6,1,2,2,3,7,4,4,4)

which compiles but with a duplicate method.

➜  snips scala-cli run --server=false -S 3.7.0 even-sums.scala
Exception in thread "main" java.lang.ClassFormatError: Duplicate method name "even$minussums$package$$$_$_$$anonfun$$anonfun$1" with signature "(I)Z" in class file even$minussums$package$
        at java.base/java.lang.ClassLoader.defineClass1(Native Method)
        at java.base/java.lang.ClassLoader.defineClass(ClassLoader.java:1026)
        at java.base/java.security.SecureClassLoader.defineClass(SecureClassLoader.java:150)
        at java.base/jdk.internal.loader.BuiltinClassLoader.defineClass(BuiltinClassLoader.java:862)
        at java.base/jdk.internal.loader.BuiltinClassLoader.findClassOnClassPathOrNull(BuiltinClassLoader.java:760)
        at java.base/jdk.internal.loader.BuiltinClassLoader.loadClassOrNull(BuiltinClassLoader.java:681)
        at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:639)
        at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:188)
        at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:528)
        at test.main(even-sums.scala:21)

visible at lambdalift.

[[syntax trees at end of MegaPhase{lambdaLift, elimStaticThis, countOuterAccesses}]] // /home/amarki/snips/even-sums.scala
package <empty> {
  final lazy module val even-sums$package: even-sums$package =
    new even-sums$package()
  @SourceFile("even-sums.scala") final module class even-sums$package extends
    Object {
    def <init>(): Unit =
      {
        super()
        ()
      }
    private def writeReplace(): Object =
      new scala.runtime.ModuleSerializationProxy(classOf[even-sums$package])
    def pf(): PartialFunction =
      {
        new
          scala.runtime.AbstractPartialFunction with java.io.Serializable {...}(
          ):scala.runtime.AbstractPartialFunction
      }
    @main def test(): Unit =
      println(
        pf().apply(
          List().apply(
            scala.runtime.ScalaRunTime.wrapIntArray(
              [2,4,6,1,2,2,3,7,4,4,4 : Int])
          )
        )
      )
    private final <static> def $anonfun$$anonfun$1(_$2: Int): Boolean =
      _$2.%(2).==(0)
    private final <static> def $anonfun$$anonfun$1(_$2: Int): Boolean =
      _$2.%(2).==(0)

I intended to get back to this. The San Francisco Giants lost today, so I need a pick-me-up.