`StringFormatter.showArg` throws `NullPointerException`

[xuwei-k]

Compiler version

3.1.0-RC1 and 3.1.0-RC1-bin-20210831-adefa48-NIGHTLY

Minimized code

scalacOptions ++= Seq("-source", "3.0-migration")

scalaVersion := "3.1.0-RC1"

case class A(enum: List[Int] = Nil)

Output (click arrow to expand)

[error] ## Exception when compiling 1 sources to /Users/kenji/enum-null/target/scala-3.1.0-RC1/classes
[error] java.lang.NullPointerException
[error] dotty.tools.dotc.printing.Formatting$StringFormatter.showArg(Formatting.scala:39)
[error] dotty.tools.dotc.printing.Formatting$StringFormatter.treatArg(Formatting.scala:49)
[error] dotty.tools.dotc.printing.Formatting$StringFormatter.$anonfun$2(Formatting.scala:62)
[error] scala.collection.LazyZip2$$anon$1$$anon$2.next(LazyZipOps.scala:42)
[error] scala.collection.mutable.Growable.addAll(Growable.scala:62)
[error] scala.collection.mutable.Growable.addAll$(Growable.scala:57)
[error] scala.collection.mutable.ArrayBuilder.addAll(ArrayBuilder.scala:66)
[error] scala.collection.IterableOnceOps.toArray(IterableOnce.scala:1282)
[error] scala.collection.IterableOnceOps.toArray$(IterableOnce.scala:1276)
[error] scala.collection.AbstractIterable.toArray(Iterable.scala:919)
[error] scala.Array$.from(Array.scala:73)
[error] scala.collection.immutable.ArraySeq$.from(ArraySeq.scala:274)
[error] scala.collection.immutable.ArraySeq$.from(ArraySeq.scala:265)
[error] scala.collection.ClassTagIterableFactory$AnyIterableDelegate.from(Factory.scala:671)
[error] scala.collection.BuildFromLowPriority2$$anon$11.fromSpecific(BuildFrom.scala:112)
[error] scala.collection.BuildFromLowPriority2$$anon$11.fromSpecific(BuildFrom.scala:109)
[error] scala.collection.LazyZip2.map(LazyZipOps.scala:37)
[error] dotty.tools.dotc.printing.Formatting$StringFormatter.assemble(Formatting.scala:62)
[error] dotty.tools.dotc.core.Decorators$.i(Decorators.scala:276)
[error] dotty.tools.dotc.parsing.Scanners$Scanner.treatAsIdent$$anonfun$1(Scanners.scala:251)
[error] dotty.tools.dotc.reporting.NoExplanation.msg(Message.scala:132)
[error] dotty.tools.dotc.reporting.Message.message(Message.scala:87)
[error] dotty.tools.dotc.reporting.Message.isNonSensical(Message.scala:99)
[error] dotty.tools.dotc.reporting.HideNonSensicalMessages.isHidden(HideNonSensicalMessages.scala:16)
[error] dotty.tools.dotc.reporting.HideNonSensicalMessages.isHidden$(HideNonSensicalMessages.scala:10)
[error] dotty.tools.dotc.reporting.AbstractReporter.isHidden(AbstractReporter.scala:8)
[error] dotty.tools.dotc.reporting.Reporter.go$3$$anonfun$2(Reporter.scala:161)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
[error] scala.Option.foreach(Option.scala:437)
[error] dotty.tools.dotc.reporting.Reporter.go$1(Reporter.scala:174)
[error] dotty.tools.dotc.reporting.Reporter.issueIfNotSuppressed(Reporter.scala:184)
[error] dotty.tools.dotc.Run.reportSuspendedMessages$$anonfun$3$$anonfun$1(Run.scala:140)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
[error] scala.collection.mutable.LinkedHashSet.foreach(LinkedHashSet.scala:127)
[error] dotty.tools.dotc.Run.dotty$tools$dotc$Run$suppressions$$$_$reportSuspendedMessages$$anonfun$1(Run.scala:140)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
[error] scala.Option.foreach(Option.scala:437)
[error] dotty.tools.dotc.Run$suppressions$.reportSuspendedMessages(Run.scala:140)
[error] dotty.tools.dotc.typer.TyperPhase.liftedTree1$1(TyperPhase.scala:60)
[error] dotty.tools.dotc.typer.TyperPhase.typeCheck$$anonfun$1(TyperPhase.scala:62)
[error] dotty.tools.dotc.core.Phases$Phase.monitor(Phases.scala:411)
[error] dotty.tools.dotc.typer.TyperPhase.typeCheck(TyperPhase.scala:63)
[error] dotty.tools.dotc.typer.TyperPhase.runOn$$anonfun$1(TyperPhase.scala:105)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
[error] scala.collection.immutable.List.foreach(List.scala:333)
[error] dotty.tools.dotc.typer.TyperPhase.runOn(TyperPhase.scala:105)
[error] dotty.tools.dotc.Run.runPhases$4$$anonfun$4(Run.scala:261)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
[error] scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1323)
[error] dotty.tools.dotc.Run.runPhases$5(Run.scala:272)
[error] dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:280)
[error] scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.scala:18)
[error] dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:68)
[error] dotty.tools.dotc.Run.compileUnits(Run.scala:289)
[error] dotty.tools.dotc.Run.compileSources(Run.scala:222)
[error] dotty.tools.dotc.Run.compile(Run.scala:206)
[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:91)
[error] sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$7(MixedAnalyzingCompiler.scala:192)
[error] scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:23)
[error] sbt.internal.inc.MixedAnalyzingCompiler.timed(MixedAnalyzingCompiler.scala:247)
[error] sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$4(MixedAnalyzingCompiler.scala:182)
[error] sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$4$adapted(MixedAnalyzingCompiler.scala:163)
[error] sbt.internal.inc.JarUtils$.withPreviousJar(JarUtils.scala:239)
[error] sbt.internal.inc.MixedAnalyzingCompiler.compileScala$1(MixedAnalyzingCompiler.scala:163)
[error] sbt.internal.inc.MixedAnalyzingCompiler.compile(MixedAnalyzingCompiler.scala:210)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1(IncrementalCompilerImpl.scala:528)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1$adapted(IncrementalCompilerImpl.scala:528)
[error] sbt.internal.inc.Incremental$.$anonfun$apply$5(Incremental.scala:175)
[error] sbt.internal.inc.Incremental$.$anonfun$apply$5$adapted(Incremental.scala:173)
[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$$anon$1.next(IncrementalCommon.scala:52)
[error] sbt.internal.inc.IncrementalCommon.cycle(IncrementalCommon.scala:263)
[error] sbt.internal.inc.Incremental$.$anonfun$incrementalCompile$8(Incremental.scala:414)
[error] sbt.internal.inc.Incremental$.withClassfileManager(Incremental.scala:501)
[error] sbt.internal.inc.Incremental$.incrementalCompile(Incremental.scala:401)
[error] sbt.internal.inc.Incremental$.apply(Incremental.scala:167)
[error] sbt.internal.inc.IncrementalCompilerImpl.compileInternal(IncrementalCompilerImpl.scala:528)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileIncrementally$1(IncrementalCompilerImpl.scala:482)
[error] sbt.internal.inc.IncrementalCompilerImpl.handleCompilationError(IncrementalCompilerImpl.scala:332)
[error] sbt.internal.inc.IncrementalCompilerImpl.compileIncrementally(IncrementalCompilerImpl.scala:420)
[error] sbt.internal.inc.IncrementalCompilerImpl.compile(IncrementalCompilerImpl.scala:137)
[error] sbt.Defaults$.compileIncrementalTaskImpl(Defaults.scala:2357)
[error] sbt.Defaults$.$anonfun$compileIncrementalTask$2(Defaults.scala:2314)
[error] sbt.internal.io.Retry$.apply(Retry.scala:46)
[error] sbt.internal.io.Retry$.apply(Retry.scala:28)
[error] sbt.internal.io.Retry$.apply(Retry.scala:23)
[error] sbt.internal.server.BspCompileTask$.compute(BspCompileTask.scala:31)
[error] sbt.Defaults$.$anonfun$compileIncrementalTask$1(Defaults.scala:2310)
[error] scala.Function1.$anonfun$compose$1(Function1.scala:49)
[error] sbt.internal.util.$tilde$greater.$anonfun$$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$2.call(CompletionService.scala:64)
[error] java.util.concurrent.FutureTask.run(FutureTask.java:266)
[error] java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
[error] java.util.concurrent.FutureTask.run(FutureTask.java:266)
[error] java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
[error] java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
[error] java.lang.Thread.run(Thread.java:748)

[som-snytt]

Maybe some interaction with incremental compilation, but the message is at treatAsIdent:

i"$name is now a keyword, write `$name` instead of $name to keep it as an identifier"

where toToken(name: SimpleName) -> handleMigration(kw: Token) -> treatAsIdent() where the name param is dropped and this.name is used.

That matters because finishNamed(Token, target: TokenData) passes target.name, which could be different from this.name (which might be null).

The name should be passed down the stack to treatAsIdent.

It would also be great to run under modern JVM with "helpful NPE", but in this case it's arg.toString that throws, where the arg is the name in the interpolation.

edit

java.lang.NullPointerException: Cannot invoke "Object.toString()" because "arg" is null while compiling keyword.scala

[griggt]

Regressed in #12857

[som-snytt]

I haven't finished looking at the different calls to finishNamed but #13442

The token data of interest may not be this.

I can't tell if my baseball team is more likely to win if I'm watching or ignoring them.

Edit: it seems to work if I ignore them and do some coding, at least the Giants tied it up.

There is already an array of strings for keywords so it's nice to use it.

Edit: Giants gave up a run and now have an impossible task. Edit: they had a huge chance and can't get a run in.

[som-snytt]

I didn't get a response to any comment.