Compiler Crashes when extending a trait containing an abstract inline in different project

[joschua-fink]

Minimized code

// in project A
trait A {
  inline def a: Int
}

// in project B
trait B extends A {
  inline def a: Int = 0
}

Output

Compiler crash in Scala 3.0.0-M3 when trying to compile project B.

[error] scala.MatchError: 17 (of class java.lang.Integer)
[error] dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readConstant(TreeUnpickler.scala:288)
[error] dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readSimpleType$1(TreeUnpickler.scala:438)
[error] dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readType(TreeUnpickler.scala:441)
[error] dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readPathTerm$1(TreeUnpickler.scala:1048)
[error] dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readSimpleTerm$1(TreeUnpickler.scala:1112)
[error] dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readTerm(TreeUnpickler.scala:1262)
[error] dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.createMemberSymbol$$anonfun$1(TreeUnpickler.scala:610)
[error] dotty.tools.dotc.core.Annotations$.dotty$tools$dotc$core$Annotations$$anon$1$$_$$lessinit$greater$$anonfun$1(Annotations.scala:127)
[error] dotty.tools.dotc.core.Annotations$LazyBodyAnnotation.tree(Annotations.scala:115)
[error] dotty.tools.dotc.typer.Inliner$.bodyToInline(Inliner.scala:47)
[error] dotty.tools.dotc.sbt.ExtractAPICollector.apiAnnotations(ExtractAPI.scala:589)
[error] dotty.tools.dotc.sbt.ExtractAPICollector.apiDef(ExtractAPI.scala:369)
[error] dotty.tools.dotc.sbt.ExtractAPICollector.apiDefinition(ExtractAPI.scala:338)
[error] dotty.tools.dotc.sbt.ExtractAPICollector.apiDefinitions$$anonfun$1(ExtractAPI.scala:323)
[error] scala.collection.immutable.List.map(List.scala:250)
[error] dotty.tools.dotc.sbt.ExtractAPICollector.apiDefinitions(ExtractAPI.scala:323)
[error] dotty.tools.dotc.sbt.ExtractAPICollector.$anonfun$7(ExtractAPI.scala:284)
[error] dotty.tools.dotc.sbt.ThunkHolder.$anonfun$1(ThunkHolder.scala:28)
[error] xsbti.api.SafeLazy$Impl.get(SafeLazy.java:64)
[error] dotty.tools.dotc.sbt.ThunkHolder.forceThunks$$anonfun$1(ThunkHolder.scala:19)
[error] scala.collection.immutable.List.foreach(List.scala:333)
[error] dotty.tools.dotc.sbt.ThunkHolder.forceThunks(ThunkHolder.scala:19)
[error] dotty.tools.dotc.sbt.ThunkHolder.forceThunks$(ThunkHolder.scala:12)
[error] dotty.tools.dotc.sbt.ExtractAPICollector.forceThunks(ExtractAPI.scala:129)
[error] dotty.tools.dotc.sbt.ExtractAPICollector.apiSource(ExtractAPI.scala:189)
[error] dotty.tools.dotc.sbt.ExtractAPI.run(ExtractAPI.scala:68)
[error] dotty.tools.dotc.core.Phases$Phase.runOn$$anonfun$1(Phases.scala:296)
[error] scala.collection.immutable.List.map(List.scala:246)
[error] dotty.tools.dotc.core.Phases$Phase.runOn(Phases.scala:297)
[error] dotty.tools.dotc.Run.runPhases$4$$anonfun$4(Run.scala:185)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
[error] scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1323)
[error] dotty.tools.dotc.Run.runPhases$5(Run.scala:195)
[error] dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:203)
[error] scala.runtime.function.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:12)
[error] dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:67)
[error] dotty.tools.dotc.Run.compileUnits(Run.scala:210)
[error] dotty.tools.dotc.Run.compileSources(Run.scala:146)
[error] dotty.tools.dotc.Run.compile(Run.scala:130)
[error] dotty.tools.dotc.Driver.doCompile(Driver.scala:39)
[error] dotty.tools.xsbt.CompilerBridgeDriver.run(CompilerBridgeDriver.java:88)
[error] dotty.tools.xsbt.CompilerBridge.run(CompilerBridge.java:22)
[error] sbt.internal.inc.AnalyzingCompiler.compile(AnalyzingCompiler.scala:92)
[error] sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$7(MixedAnalyzingCompiler.scala:186)
[error] scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:23)
[error] sbt.internal.inc.MixedAnalyzingCompiler.timed(MixedAnalyzingCompiler.scala:241)
[error] sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$4(MixedAnalyzingCompiler.scala:176)
[error] sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$4$adapted(MixedAnalyzingCompiler.scala:157)
[error] sbt.internal.inc.JarUtils$.withPreviousJar(JarUtils.scala:239)
[error] sbt.internal.inc.MixedAnalyzingCompiler.compileScala$1(MixedAnalyzingCompiler.scala:157)
[error] sbt.internal.inc.MixedAnalyzingCompiler.compile(MixedAnalyzingCompiler.scala:204)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1(IncrementalCompilerImpl.scala:573)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1$adapted(IncrementalCompilerImpl.scala:573)
[error] sbt.internal.inc.Incremental$.$anonfun$apply$5(Incremental.scala:174)
[error] sbt.internal.inc.Incremental$.$anonfun$apply$5$adapted(Incremental.scala:172)
[error] sbt.internal.inc.Incremental$$anon$2.run(Incremental.scala:459)
[error] sbt.internal.inc.IncrementalCommon$CycleState.next(IncrementalCommon.scala:116)
[error] sbt.internal.inc.IncrementalCommon$$anon$1.next(IncrementalCommon.scala:56)
[error] sbt.internal.inc.IncrementalCommon$$anon$1.next(IncrementalCommon.scala:52)
[error] sbt.internal.inc.IncrementalCommon.cycle(IncrementalCommon.scala:261)
[error] sbt.internal.inc.Incremental$.$anonfun$incrementalCompile$8(Incremental.scala:414)
[error] sbt.internal.inc.Incremental$.withClassfileManager(Incremental.scala:499)
[error] sbt.internal.inc.Incremental$.incrementalCompile(Incremental.scala:401)
[error] sbt.internal.inc.Incremental$.apply(Incremental.scala:166)
[error] sbt.internal.inc.IncrementalCompilerImpl.compileInternal(IncrementalCompilerImpl.scala:573)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileIncrementally$1(IncrementalCompilerImpl.scala:491)
[error] sbt.internal.inc.IncrementalCompilerImpl.handleCompilationError(IncrementalCompilerImpl.scala:332)
[error] sbt.internal.inc.IncrementalCompilerImpl.compileIncrementally(IncrementalCompilerImpl.scala:420)
[error] sbt.internal.inc.IncrementalCompilerImpl.compile(IncrementalCompilerImpl.scala:137)
[error] sbt.Defaults$.compileIncrementalTaskImpl(Defaults.scala:2177)
[error] sbt.Defaults$.$anonfun$compileIncrementalTask$2(Defaults.scala:2134)
[error] sbt.internal.io.Retry$.apply(Retry.scala:40)
[error] sbt.internal.io.Retry$.apply(Retry.scala:23)
[error] sbt.internal.server.BspCompileTask$.compute(BspCompileTask.scala:31)
[error] sbt.Defaults$.$anonfun$compileIncrementalTask$1(Defaults.scala:2130)
[error] scala.Function1.$anonfun$compose$1(Function1.scala:49)
[error] sbt.internal.util.$tilde$greater.$anonfun$$u2219$1(TypeFunctions.scala:62)
[error] sbt.std.Transform$$anon$4.work(Transform.scala:68)
[error] sbt.Execute.$anonfun$submit$2(Execute.scala:282)
[error] sbt.internal.util.ErrorHandling$.wideConvert(ErrorHandling.scala:23)
[error] sbt.Execute.work(Execute.scala:291)
[error] sbt.Execute.$anonfun$submit$1(Execute.scala:282)
[error] sbt.ConcurrentRestrictions$$anon$4.$anonfun$submitValid$1(ConcurrentRestrictions.scala:265)
[error] sbt.CompletionService$$anon$2.call(CompletionService.scala:64)
[error] java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
[error] java.base/java.util.concurrent.Executors$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:832)
[error]
[error] stack trace is suppressed; run 'last project2 / Compile / compileIncremental' for the full output
[error] (project2 / Compile / compileIncremental) scala.MatchError: 17 (of class java.lang.Integer)
[error] Total time: 1 s, completed 12.01.2021, 16:04:39

Expectation

No crash :-)

Notes

I would be thankful for a quick workaround. So far I haven't found one.

// in project A
trait A {
  inline def a: Int
}

trait A0 extends A {
  inline def a: Int = 0
}

// in project B
trait B extends A0

crashes also in project B. And so does exporting project A as library instead of depending on it via dependsOn in sbt.

[joschua-fink]

I'm also getting the same compiler error from time to time in a single project, after updating a source file containing inlines, when dotty tries to partially recompile the project. Running a clean in sbt in the project to force a full recompile, solves the problem in this situation.

[odersky]

I can't reproduce this. I tried the two files as given, compiled first A and then B. That worked OK.

[smarter]

The crash is in ExtractAPI, when not running in sbt that phase isn't run by default, but you can enable it with -Yforce-sbt-phases, that should help reproduce the problem.

[odersky]

Ah, now I can reproduce.