-Yinfer-argument-types is not rejected as bad option but code using it causes the typechecker to crash

[rcano]

Trying to compile in dotty some code that compiles fine in scalac I found this issue. Dottyc does warn about other invalid settings but not this one, and code like

new EventHandler[Evt] {
 override def handle(evt) = ???
}

causes the typechecker to crash.

[allanrenucci]

Could you give an example file that makes the typechecker crash, I cannot reproduce your issue

[rcano]

@allanrenucci here you go

class crash extends java.util.concurrent.ThreadFactory {
  override def newThread(r) = new Thread(r)
}

compile with scalacOptions ++= Seq("-Yinfer-argument-types")

[allanrenucci]

Thanks! I can reproduce with dotc -Yinfer-argument-types crash.scala:

Stacktrace

[info] Running dotty.tools.dotc.Main -classpath /Users/renucci/projects/dotty/library/target/scala-2.12/dotty-library_2.12-0.5.0-bin-SNAPSHOT-nonbootstrapped.jar -d out tests/allan/Test.scala -Yinfer-argument-types
exception occurred while typechecking tests/allan/Test.scala
exception occurred while compiling tests/allan/Test.scala
Exception in thread "main" java.lang.AssertionError: assertion failed
	at scala.Predef$.assert(Predef.scala:204)
	at dotty.tools.dotc.ast.Trees$Tree.withType(Trees.scala:121)
	at dotty.tools.dotc.typer.Typer.$anonfun$typedTypeTree$1(Typer.scala:1072)
	at dotty.tools.dotc.util.Stats$.track(Stats.scala:35)
	at dotty.tools.dotc.typer.Typer.typedTypeTree(Typer.scala:1057)
	at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:1662)
	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:1690)
	at dotty.tools.dotc.typer.Typer.$anonfun$typed$2(Typer.scala:1707)
	at dotty.tools.dotc.reporting.trace$.apply(trace.scala:23)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:1703)
	at dotty.tools.dotc.typer.Namer.$anonfun$typedAheadType$1(Namer.scala:939)
	at dotty.tools.dotc.typer.Namer.typedAheadImpl(Namer.scala:932)
	at dotty.tools.dotc.typer.Namer.typedAheadType(Namer.scala:939)
	at dotty.tools.dotc.typer.Namer.valOrDefDefSig(Namer.scala:1115)
	at dotty.tools.dotc.typer.Namer$Completer.typeSig(Namer.scala:732)
	at dotty.tools.dotc.typer.Namer$Completer.completeInCreationContext(Namer.scala:780)
	at dotty.tools.dotc.typer.Namer$Completer.complete(Namer.scala:758)
	at dotty.tools.dotc.core.SymDenotations$SymDenotation.completeFrom(SymDenotations.scala:241)
	at dotty.tools.dotc.core.SymDenotations$SymDenotation.completeInfo$1(SymDenotations.scala:204)
	at dotty.tools.dotc.core.SymDenotations$SymDenotation.info(SymDenotations.scala:206)
	at dotty.tools.dotc.core.SymDenotations$SymDenotation.ensureCompleted(SymDenotations.scala:347)
	at dotty.tools.dotc.typer.Typer.retrieveSym(Typer.scala:1595)
	at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:1620)
	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:1689)
	at dotty.tools.dotc.typer.Typer.$anonfun$typed$2(Typer.scala:1707)
	at dotty.tools.dotc.reporting.trace$.apply(trace.scala:23)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:1703)
	at dotty.tools.dotc.typer.Namer.$anonfun$typedAheadExpr$1(Namer.scala:942)
	at dotty.tools.dotc.typer.Namer.typedAheadImpl(Namer.scala:932)
	at dotty.tools.dotc.typer.Namer.typedAheadExpr(Namer.scala:942)
	at dotty.tools.dotc.typer.Namer.$anonfun$completeParams$1(Namer.scala:954)
	at scala.collection.immutable.List.foreach(List.scala:389)
	at dotty.tools.dotc.typer.Namer.completeParams(Namer.scala:954)
	at dotty.tools.dotc.typer.Namer.$anonfun$defDefSig$3(Namer.scala:1150)
	at dotty.tools.dotc.typer.Namer.$anonfun$defDefSig$3$adapted(Namer.scala:1150)
	at scala.collection.immutable.List.foreach(List.scala:389)
	at dotty.tools.dotc.typer.Namer.defDefSig(Namer.scala:1150)
	at dotty.tools.dotc.typer.Namer$Completer.typeSig(Namer.scala:736)
	at dotty.tools.dotc.typer.Namer$Completer.completeInCreationContext(Namer.scala:780)
	at dotty.tools.dotc.typer.Namer$Completer.complete(Namer.scala:758)
	at dotty.tools.dotc.core.SymDenotations$SymDenotation.completeFrom(SymDenotations.scala:241)
	at dotty.tools.dotc.core.SymDenotations$SymDenotation.completeInfo$1(SymDenotations.scala:204)
	at dotty.tools.dotc.core.SymDenotations$SymDenotation.info(SymDenotations.scala:206)
	at dotty.tools.dotc.core.SymDenotations$SymDenotation.ensureCompleted(SymDenotations.scala:347)
	at dotty.tools.dotc.typer.Typer.retrieveSym(Typer.scala:1595)
	at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:1620)
	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:1689)
	at dotty.tools.dotc.typer.Typer.$anonfun$typed$2(Typer.scala:1707)
	at dotty.tools.dotc.reporting.trace$.apply(trace.scala:23)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:1703)
	at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:1729)
	at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:1752)
	at dotty.tools.dotc.typer.Typer.$anonfun$typedClassDef$1(Typer.scala:1415)
	at dotty.tools.dotc.util.Stats$.track(Stats.scala:35)
	at dotty.tools.dotc.typer.Typer.typedClassDef(Typer.scala:1345)
	at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:1633)
	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:1689)
	at dotty.tools.dotc.typer.Typer.$anonfun$typed$2(Typer.scala:1707)
	at dotty.tools.dotc.reporting.trace$.apply(trace.scala:23)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:1703)
	at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:1729)
	at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:1752)
	at dotty.tools.dotc.typer.Typer.$anonfun$typedPackageDef$1(Typer.scala:1528)
	at dotty.tools.dotc.util.Stats$.track(Stats.scala:35)
	at dotty.tools.dotc.typer.Typer.typedPackageDef(Typer.scala:1515)
	at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:1672)
	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:1690)
	at dotty.tools.dotc.typer.Typer.$anonfun$typed$2(Typer.scala:1707)
	at dotty.tools.dotc.reporting.trace$.apply(trace.scala:23)
	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:1703)
	at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:1764)
	at dotty.tools.dotc.typer.FrontEnd.$anonfun$typeCheck$1(FrontEnd.scala:64)
	at dotty.tools.dotc.typer.FrontEnd.monitor(FrontEnd.scala:32)
	at dotty.tools.dotc.typer.FrontEnd.typeCheck(FrontEnd.scala:62)
	at dotty.tools.dotc.typer.FrontEnd.$anonfun$runOn$7(FrontEnd.scala:93)
	at dotty.tools.dotc.typer.FrontEnd.$anonfun$runOn$7$adapted(FrontEnd.scala:93)
	at scala.collection.immutable.List.foreach(List.scala:389)
	at dotty.tools.dotc.typer.FrontEnd.runOn(FrontEnd.scala:93)
	at dotty.tools.dotc.Run.$anonfun$compileUnits$3(Run.scala:125)
	at scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:12)
	at dotty.tools.dotc.util.Stats$.trackTime(Stats.scala:47)
	at dotty.tools.dotc.Run.$anonfun$compileUnits$2(Run.scala:123)
	at dotty.tools.dotc.Run.$anonfun$compileUnits$2$adapted(Run.scala:121)
	at scala.collection.IndexedSeqOptimized.foreach(IndexedSeqOptimized.scala:32)
	at scala.collection.IndexedSeqOptimized.foreach$(IndexedSeqOptimized.scala:29)
	at scala.collection.mutable.ArrayOps$ofRef.foreach(ArrayOps.scala:191)
	at dotty.tools.dotc.Run.runPhases$1(Run.scala:121)
	at dotty.tools.dotc.Run.$anonfun$compileUnits$1(Run.scala:141)
	at scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:12)
	at dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:86)
	at dotty.tools.dotc.Run.compileUnits(Run.scala:107)
	at dotty.tools.dotc.Run.compileSources(Run.scala:94)
	at dotty.tools.dotc.Run.compile(Run.scala:78)
	at dotty.tools.dotc.Driver.doCompile(Driver.scala:29)
	at dotty.tools.dotc.Driver.process(Driver.scala:127)
	at dotty.tools.dotc.Driver.process(Driver.scala:96)
	at dotty.tools.dotc.Driver.process(Driver.scala:108)
	at dotty.tools.dotc.Driver.main(Driver.scala:135)
	at dotty.tools.dotc.Main.main(Main.scala)
 

However -Y settings are private settings. We should definitely fix the crash but I can't guaranty we will ever support this feature.

[rcano]

However -Y settings are private settings. We should definitely fix the crash but I can't guaranty we will ever support this feature.

Naturally, I reported it because unlike other scalac options which dotc rejected, this was not (and also a crash looks is bad).
Support for this feature would be something I'd like (obviously) since it's so good for refactoring and staying DRY.