Compiler crash with (f:AnyRef => AnyRef)

[jarno-r]

Compiler version

3.3.3 and 3.4.0
Works fine in Scala 2.

Minimized code

val selfie : (AnyRef => AnyRef) => AnyRef = (f:AnyRef => AnyRef) => f(f)

Output (click arrow to expand)

       during phase: MegaPhase{lambdaLift, elimStaticThis, countOuterAccesses}
                mode: Mode(ImplicitsEnabled)
     library version: version 2.13.12
    compiler version: version 3.3.3

[error] ## Exception when compiling 3 sources to /home/jarno/projects/higher-order-logic-scala/target/scala-3.3.3/classes
[error] java.lang.IllegalArgumentException: Could not find proxy for f: Function1 in [parameter f, method $anonfun, value selfie, method basic, package object Intuitionistic$package, package logic, package <root>], encl = method basic, owners = method basic, package object Intuitionistic$package, package logic, package <root>; enclosures = method basic, package object Intuitionistic$package, package logic, package <root>
[error] dotty.tools.dotc.transform.LambdaLift$Lifter.searchIn$1(LambdaLift.scala:135)
[error] dotty.tools.dotc.transform.LambdaLift$Lifter.proxy(LambdaLift.scala:148)
[error] dotty.tools.dotc.transform.LambdaLift$Lifter.proxyRef(LambdaLift.scala:166)
[error] dotty.tools.dotc.transform.LambdaLift.transformIdent(LambdaLift.scala:285)
[error] dotty.tools.dotc.transform.MegaPhase.goIdent(MegaPhase.scala:609)
[error] dotty.tools.dotc.transform.MegaPhase.transformNamed$1(MegaPhase.scala:228)
[error] dotty.tools.dotc.transform.MegaPhase.transformTree(MegaPhase.scala:440)
[error] dotty.tools.dotc.transform.MegaPhase.mapValDef$1(MegaPhase.scala:239)
[error] dotty.tools.dotc.transform.MegaPhase.transformNamed$1(MegaPhase.scala:244)
[error] dotty.tools.dotc.transform.MegaPhase.transformTree(MegaPhase.scala:440)
[error] dotty.tools.dotc.transform.MegaPhase.loop$2(MegaPhase.scala:459)
[error] dotty.tools.dotc.transform.MegaPhase.transformBlock(MegaPhase.scala:464)
[error] dotty.tools.dotc.transform.MegaPhase.transformUnnamed$1(MegaPhase.scala:303)
[error] dotty.tools.dotc.transform.MegaPhase.transformTree(MegaPhase.scala:442)
[error] dotty.tools.dotc.transform.MegaPhase.mapDefDef$1(MegaPhase.scala:253)
[error] dotty.tools.dotc.transform.MegaPhase.transformNamed$1(MegaPhase.scala:256)
[error] dotty.tools.dotc.transform.MegaPhase.transformTree(MegaPhase.scala:440)
[error] dotty.tools.dotc.transform.MegaPhase.loop$1(MegaPhase.scala:453)
[error] dotty.tools.dotc.transform.MegaPhase.transformStats(MegaPhase.scala:453)
[error] dotty.tools.dotc.transform.MegaPhase.transformUnnamed$1(MegaPhase.scala:364)
[error] dotty.tools.dotc.transform.MegaPhase.transformTree(MegaPhase.scala:442)
[error] dotty.tools.dotc.transform.MegaPhase.transformNamed$1(MegaPhase.scala:260)
[error] dotty.tools.dotc.transform.MegaPhase.transformTree(MegaPhase.scala:440)
[error] dotty.tools.dotc.transform.MegaPhase.loop$1(MegaPhase.scala:453)
[error] dotty.tools.dotc.transform.MegaPhase.transformStats(MegaPhase.scala:453)
[error] dotty.tools.dotc.transform.MegaPhase.mapPackage$1(MegaPhase.scala:384)
[error] dotty.tools.dotc.transform.MegaPhase.transformUnnamed$1(MegaPhase.scala:387)
[error] dotty.tools.dotc.transform.MegaPhase.transformTree(MegaPhase.scala:442)
[error] dotty.tools.dotc.transform.MegaPhase.transformUnit(MegaPhase.scala:469)
[error] dotty.tools.dotc.transform.MegaPhase.run(MegaPhase.scala:481)
[error] dotty.tools.dotc.core.Phases$Phase.runOn$$anonfun$1(Phases.scala:327)
[error] scala.collection.immutable.List.map(List.scala:250)
[error] dotty.tools.dotc.core.Phases$Phase.runOn(Phases.scala:331)
[error] dotty.tools.dotc.Run.runPhases$1$$anonfun$1(Run.scala:246)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
[error] scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1323)
[error] dotty.tools.dotc.Run.runPhases$1(Run.scala:262)
[error] dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:270)
[error] dotty.tools.dotc.Run.compileUnits$$anonfun$adapted$1(Run.scala:279)
[error] dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:71)
[error] dotty.tools.dotc.Run.compileUnits(Run.scala:279)
[error] dotty.tools.dotc.Run.compileSources(Run.scala:194)
[error] dotty.tools.dotc.Run.compile(Run.scala:179)
[error] dotty.tools.dotc.Driver.doCompile(Driver.scala:37)
[error] dotty.tools.xsbt.CompilerBridgeDriver.run(CompilerBridgeDriver.java:136)
[error] dotty.tools.xsbt.CompilerBridge.run(CompilerBridge.java:22)
[error] sbt.internal.inc.AnalyzingCompiler.compile(AnalyzingCompiler.scala:91)
[error] sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$7(MixedAnalyzingCompiler.scala:193)
[error] scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:23)
[error] sbt.internal.inc.MixedAnalyzingCompiler.timed(MixedAnalyzingCompiler.scala:248)
[error] sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$4(MixedAnalyzingCompiler.scala:183)
[error] sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$4$adapted(MixedAnalyzingCompiler.scala:163)
[error] sbt.internal.inc.JarUtils$.withPreviousJar(JarUtils.scala:239)
[error] sbt.internal.inc.MixedAnalyzingCompiler.compileScala$1(MixedAnalyzingCompiler.scala:163)
[error] sbt.internal.inc.MixedAnalyzingCompiler.compile(MixedAnalyzingCompiler.scala:211)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1(IncrementalCompilerImpl.scala:534)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1$adapted(IncrementalCompilerImpl.scala:534)
[error] sbt.internal.inc.Incremental$.$anonfun$apply$5(Incremental.scala:180)
[error] sbt.internal.inc.Incremental$.$anonfun$apply$5$adapted(Incremental.scala:178)
[error] sbt.internal.inc.Incremental$$anon$2.run(Incremental.scala:464)
[error] sbt.internal.inc.IncrementalCommon$CycleState.next(IncrementalCommon.scala:116)
[error] sbt.internal.inc.IncrementalCommon$$anon$1.next(IncrementalCommon.scala:56)
[error] sbt.internal.inc.IncrementalCommon$$anon$1.next(IncrementalCommon.scala:52)
[error] sbt.internal.inc.IncrementalCommon.cycle(IncrementalCommon.scala:263)
[error] sbt.internal.inc.Incremental$.$anonfun$incrementalCompile$8(Incremental.scala:419)
[error] sbt.internal.inc.Incremental$.withClassfileManager(Incremental.scala:506)
[error] sbt.internal.inc.Incremental$.incrementalCompile(Incremental.scala:406)
[error] sbt.internal.inc.Incremental$.apply(Incremental.scala:172)
[error] sbt.internal.inc.IncrementalCompilerImpl.compileInternal(IncrementalCompilerImpl.scala:534)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileIncrementally$1(IncrementalCompilerImpl.scala:488)
[error] sbt.internal.inc.IncrementalCompilerImpl.handleCompilationError(IncrementalCompilerImpl.scala:332)
[error] sbt.internal.inc.IncrementalCompilerImpl.compileIncrementally(IncrementalCompilerImpl.scala:425)
[error] sbt.internal.inc.IncrementalCompilerImpl.compile(IncrementalCompilerImpl.scala:137)
[error] sbt.Defaults$.compileIncrementalTaskImpl(Defaults.scala:2371)
[error] sbt.Defaults$.$anonfun$compileIncrementalTask$2(Defaults.scala:2321)
[error] sbt.internal.server.BspCompileTask$.$anonfun$compute$1(BspCompileTask.scala:31)
[error] sbt.internal.io.Retry$.apply(Retry.scala:47)
[error] sbt.internal.io.Retry$.apply(Retry.scala:29)
[error] sbt.internal.io.Retry$.apply(Retry.scala:24)
[error] sbt.internal.server.BspCompileTask$.compute(BspCompileTask.scala:31)
[error] sbt.Defaults$.$anonfun$compileIncrementalTask$1(Defaults.scala:2319)
[error] scala.Function1.$anonfun$compose$1(Function1.scala:49)
[error] sbt.internal.util.$tilde$greater.$anonfun$$u2219$1(TypeFunctions.scala:63)
[error] sbt.std.Transform$$anon$4.work(Transform.scala:69)
[error] sbt.Execute.$anonfun$submit$2(Execute.scala:283)
[error] sbt.internal.util.ErrorHandling$.wideConvert(ErrorHandling.scala:24)
[error] sbt.Execute.work(Execute.scala:292)
[error] sbt.Execute.$anonfun$submit$1(Execute.scala:283)
[error] sbt.ConcurrentRestrictions$$anon$4.$anonfun$submitValid$1(ConcurrentRestrictions.scala:265)
[error] sbt.CompletionService$$anon$2.call(CompletionService.scala:65)
[error] java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
[error] java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515)
[error] java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
[error] java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130)
[error] java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:630)
[error] java.base/java.lang.Thread.run(Thread.java:831)
[error]            
[error] stack trace is suppressed; run last Compile / compileIncremental for the full output
[error] (Compile / compileIncremental) java.lang.IllegalArgumentException: Could not find proxy for f: Function1 in [parameter f, method $anonfun, value selfie, method basic, package object Intuitionistic$package, package logic, package <root>], encl = method basic, owners = method basic, package object Intuitionistic$package, package logic, package <root>; enclosures = method basic, package object Intuitionistic$package, package logic, package <root>
[error] Total time: 1 s, completed Mar 16, 2024, 7:21:36 PM

[nicolasstucki]

Minimization

def selfie: Any = (f: Any => Any) => f(f)

[nicolasstucki]

Something goes wrong in MegaPhase{elimErasedValueType, pureStats, vcElideAllocations, etaReduce, arrayApply, elimPolyFunction, tailrec, completeJavaEnums, mixin, lazyVals, memoize, nonLocalReturns, capturedVars}

[[syntax trees at end of                   erasure]] // t/Test.scala
package <empty> {
  final lazy module val Test$package: Test$package = new Test$package()
  @SourceFile("t/Test.scala") final module class Test$package() extends Object()
     {
    private def writeReplace(): Object =
      new scala.runtime.ModuleSerializationProxy(classOf[Test$package])
    def fun(): Object =
      {
        def $anonfun(f: Function1): Object = f.apply(f)
        closure($anonfun)
      }
  }
}

[[syntax trees at end of MegaPhase{elimErasedValueType, pureStats, vcElideAllocations, etaReduce, arrayApply, elimPolyFunction, tailrec, completeJavaEnums, mixin, lazyVals, memoize, nonLocalReturns, capturedVars}]] // t/Test.scala
package <empty> {
  final lazy module val Test$package: Test$package = new Test$package()
  @SourceFile("t/Test.scala") final module class Test$package() extends Object {
    super()
    private def writeReplace(): Object =
      new scala.runtime.ModuleSerializationProxy(classOf[Test$package])
    def fun(): Object = f
  }
}

[nicolasstucki]

The issue is in etaReduce.

By splitting the mini phases we get

[[syntax trees at end of                   erasure]] // t/Test.scala
package <empty> {
  final lazy module val Test$package: Test$package = new Test$package()
  @SourceFile("t/Test.scala") final module class Test$package() extends Object()
     {
    private def writeReplace(): Object =
      new scala.runtime.ModuleSerializationProxy(classOf[Test$package])
    def fun(): Object =
      {
        def $anonfun(f: Function1): Object = f.apply(f)
        closure($anonfun)
      }
  }
}

[[syntax trees at end of       elimErasedValueType]] // t/Test.scala: unchanged since erasure
[[syntax trees at end of                 pureStats]] // t/Test.scala: unchanged since erasure
[[syntax trees at end of        vcElideAllocations]] // t/Test.scala: unchanged since erasure
[[syntax trees at end of                 etaReduce]] // t/Test.scala
package <empty> {
  final lazy module val Test$package: Test$package = new Test$package()
  @SourceFile("t/Test.scala") final module class Test$package() extends Object()
     {
    private def writeReplace(): Object =
      new scala.runtime.ModuleSerializationProxy(classOf[Test$package])
    def fun(): Object = f
  }
}

[nicolasstucki]

In general, this fails on any

(x1: T1, ..., xi: Ti,  ..., xn: Tn) => xi.apply(x1, ..., xn) 

where

Ti =:= (T1, ..., Ti-1, U, Ti+1, ... Tn) => R

and

Ti <: U

This seems to be an unlikely corner case.