Compiler crash while porting from Scala 2 to Scala 3

[OndrejSpanel]

Compiler version

3.3.1 and 3.4.0-RC1

Minimized code

I do not have any. The project is large, uses multiple libraries including macros and the error is not very helpful in finding the source of the error.

Output (click arrow to expand)

[error] java.lang.AssertionError: Cannot change span of EmptyTree
[error] dotty.tools.dotc.ast.Trees$EmptyTree.withSpan(Trees.scala:1067)
[error] dotty.tools.dotc.ast.Trees$EmptyTree.withSpan(Trees.scala:1067)
[error] dotty.tools.dotc.ast.desugar$.patternsToParams$$anonfun$1(Desugar.scala:1610)
[error] scala.collection.immutable.List.map(List.scala:246)
[error] dotty.tools.dotc.ast.desugar$.patternsToParams(Desugar.scala:1610)
[error] dotty.tools.dotc.typer.Typer.typedFunctionValue(Typer.scala:1630)
[error] dotty.tools.dotc.typer.Typer.typedFunction(Typer.scala:1416)
[error] dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3170)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3244)
[error] dotty.tools.dotc.typer.ProtoTypes$FunProto.$anonfun$7(ProtoTypes.scala:509)
[error] dotty.tools.dotc.typer.ProtoTypes$FunProto.cacheTypedArg(ProtoTypes.scala:432)
[error] dotty.tools.dotc.typer.ProtoTypes$FunProto.typedArg(ProtoTypes.scala:510)
[error] dotty.tools.dotc.typer.Applications$ApplyToUntyped.typedArg(Applications.scala:912)
[error] dotty.tools.dotc.typer.Applications$ApplyToUntyped.typedArg(Applications.scala:912)
[error] dotty.tools.dotc.typer.Applications$Application.addTyped$1(Applications.scala:604)
[error] dotty.tools.dotc.typer.Applications$Application.matchArgs(Applications.scala:668)
[error] dotty.tools.dotc.typer.Applications$Application.init(Applications.scala:490)
[error] dotty.tools.dotc.typer.Applications$TypedApply.(Applications.scala:794)
[error] dotty.tools.dotc.typer.Applications$ApplyToUntyped.(Applications.scala:911)
[error] dotty.tools.dotc.typer.Applications.ApplyTo(Applications.scala:1141)
[error] dotty.tools.dotc.typer.Applications.ApplyTo$(Applications.scala:350)
[error] dotty.tools.dotc.typer.Typer.ApplyTo(Typer.scala:121)
[error] dotty.tools.dotc.typer.Applications.simpleApply$1(Applications.scala:984)
[error] dotty.tools.dotc.typer.Applications.realApply$1$$anonfun$2(Applications.scala:1067)
[error] dotty.tools.dotc.typer.Typer.tryEither(Typer.scala:3461)
[error] dotty.tools.dotc.typer.Applications.realApply$1(Applications.scala:1078)
[error] dotty.tools.dotc.typer.Applications.typedApply(Applications.scala:1116)
[error] dotty.tools.dotc.typer.Applications.typedApply$(Applications.scala:350)
[error] dotty.tools.dotc.typer.Typer.typedApply(Typer.scala:121)
[error] dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3160)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3244)
[error] dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3210)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3244)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3321)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3325)
[error] dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:3437)
[error] dotty.tools.dotc.typer.Typer.typedBlock(Typer.scala:1200)
[error] dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3168)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3244)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3321)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3325)
[error] dotty.tools.dotc.typer.Typer.typedIf(Typer.scala:1289)
[error] dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3169)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3244)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3321)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3325)
[error] dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:3374)
[error] dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:3393)
[error] dotty.tools.dotc.typer.Typer.typedBlockStats(Typer.scala:1193)
[error] dotty.tools.dotc.typer.Typer.typedBlock(Typer.scala:1197)
[error] dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3168)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3244)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3321)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3325)
[error] dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:3437)
[error] dotty.tools.dotc.typer.Typer.$anonfun$62(Typer.scala:2602)
[error] dotty.tools.dotc.inlines.PrepareInlineable$.dropInlineIfError(PrepareInlineable.scala:256)
[error] dotty.tools.dotc.typer.Typer.typedDefDef(Typer.scala:2602)
[error] dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:3136)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3243)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3321)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3325)
[error] dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:3347)
[error] dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:3393)
[error] dotty.tools.dotc.typer.Typer.typedClassDef(Typer.scala:2789)
[error] dotty.tools.dotc.typer.Typer.typedTypeOrClassDef$1(Typer.scala:3148)
[error] dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:3152)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3243)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3321)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3325)
[error] dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:3347)
[error] dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:3393)
[error] dotty.tools.dotc.typer.Typer.typedPackageDef(Typer.scala:2922)
[error] dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3194)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3244)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3321)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3325)
[error] dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:3374)
[error] dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:3393)
[error] dotty.tools.dotc.typer.Typer.typedPackageDef(Typer.scala:2922)
[error] dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3194)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3244)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3321)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3325)
[error] dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:3437)
[error] dotty.tools.dotc.typer.TyperPhase.typeCheck$$anonfun$1(TyperPhase.scala:47)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
[error] dotty.tools.dotc.core.Phases$Phase.monitor(Phases.scala:477)
[error] dotty.tools.dotc.typer.TyperPhase.typeCheck(TyperPhase.scala:53)
[error] dotty.tools.dotc.typer.TyperPhase.$anonfun$4(TyperPhase.scala:99)
[error] scala.collection.Iterator$$anon$6.hasNext(Iterator.scala:479)
[error] scala.collection.Iterator$$anon$9.hasNext(Iterator.scala:583)
[error] scala.collection.immutable.List.prependedAll(List.scala:155)
[error] scala.collection.immutable.List$.from(List.scala:684)
[error] scala.collection.immutable.List$.from(List.scala:681)
[error] scala.collection.IterableOps$WithFilter.map(Iterable.scala:898)
[error] dotty.tools.dotc.typer.TyperPhase.runOn(TyperPhase.scala:100)
[error] dotty.tools.dotc.Run.runPhases$1$$anonfun$1(Run.scala:315)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
[error] scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1323)
[error] dotty.tools.dotc.Run.runPhases$1(Run.scala:337)
[error] dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:348)
[error] dotty.tools.dotc.Run.compileUnits$$anonfun$adapted$1(Run.scala:357)
[error] dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:71)
[error] dotty.tools.dotc.Run.compileUnits(Run.scala:357)
[error] dotty.tools.dotc.Run.compileSources(Run.scala:261)
[error] dotty.tools.dotc.Run.compile(Run.scala:246)
[error] dotty.tools.dotc.Driver.doCompile(Driver.scala:37)
[error] dotty.tools.xsbt.CompilerBridgeDriver.run(CompilerBridgeDriver.java:141)
[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$2.call(CompletionService.scala:65)
[error] java.base/java.util.concurrent.FutureTask.run(FutureTask.java:317)
[error] java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:572)
[error] java.base/java.util.concurrent.FutureTask.run(FutureTask.java:317)
[error] java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144)
[error] java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642)
[error] java.base/java.lang.Thread.run(Thread.java:1583)
[error]

[bishabosha]

I see the crash is in desugaring a lambda function, however it would really help if you can share any code if possible.

If the code is able to be shared, a GitHub repo with some steps that can reproduce is enough for us to start with

[odersky]

In fact the Desugar code in question clearly has a problem. Let me fix that and we'll see whether that solves it.

[OndrejSpanel]

When/how could I test the fix? I am not in any hurry, but if there is anything to report, I would like to do it soon, in case any related problems appear.

[bishabosha]

Please observe tomorrow for the next nightly release at https://central.sonatype.com/artifact/org.scala-lang/scala3-compiler_3 (they are published around 05:00 CET)