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Illegal Array type in inline macros can cause crashes with -Ycheck #22034

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Illegal Array type in inline macros can cause crashes with -Ycheck#22034
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area:metaprogramming:otherIssues tied to metaprogramming/macros not covered by the other labels.itype:bug
@jchyb

Description

@jchyb
jchyb
opened on Nov 26, 2024

Compiler version

any

Minimized code

Macro_1.scala:

import scala.quoted._
object Macro:

  inline def test() = ${testImpl}

  def testImpl(using Quotes): Expr[Any] = {
    import quotes.reflect._
    val tpe = TypeRepr.of[Array[Byte]] match
      case AppliedType(tycons, _) => tycons
    tpe.asType match
      case '[t] => '{ List[t]() }
  }

  inline def recurTest() = ${recurTestImpl}
  def recurTestImpl(using Quotes): Expr[Any] = {
    import quotes.reflect._
    val tpe = TypeRepr.of[Array[Byte]] match
      case AppliedType(tycons, _) => AppliedType(tycons, List(tycons))
    tpe.asType match
      case '[t] =>
        '{ List[t]() }
  }

Test_2.scala

@main def Test: Unit =
  Macro.test() // error
  Macro.recurTest() // error

Output

*** error while checking i21916-b/Test_2.scala after phase erasure ***

  unhandled exception while running Ycheck on i21916-b/Test_2.scala

  An unhandled exception was thrown in the compiler.
  Please file a crash report here:
  https://github.com/scala/scala3/issues/new/choose
  For non-enriched exceptions, compile with -Xno-enrich-error-messages.


     while compiling: i21916-b/Test_2.scala
        during phase: Ycheck
                mode: Mode(ImplicitsEnabled)
     library version: version 2.13.15
    compiler version: version 3.6.4-RC1-bin-SNAPSHOT-nonbootstrapped-git-164a8ed
            settings: -Ycheck List(all) -classpath /Users/jchyb/Library/Caches/Coursier/v1/https/repo1.maven.org/maven2/org/scala-lang/scala-library/2.13.15/scala-library-2.13.15.jar:/Users/jchyb/workspace/scala3/library/../out/bootstrap/scala3-library-bootstrapped/scala-3.6.4-RC1-bin-SNAPSHOT-nonbootstrapped/scala3-library_3-3.6.4-RC1-bin-SNAPSHOT.jar
Exception in thread "main" java.lang.AssertionError: assertion failed: The type Array - TypeRef(ThisType(TypeRef(NoPrefix,module class scala)),class Array) of class class dotty.tools.dotc.core.Types$CachedTypeRef of tree Array : Array / class dotty.tools.dotc.ast.Trees$TypeTree is illegal after erasure, phase = erasure

  Exception while compiling i21916-b/Test_2.scala, i21916-b/Macro_1.scala

  An unhandled exception was thrown in the compiler.
  Please file a crash report here:
  https://github.com/scala/scala3/issues/new/choose
  For non-enriched exceptions, compile with -Xno-enrich-error-messages.


     while compiling: <no file>
        during phase: parser
                mode: Mode()
     library version: version 2.13.15
    compiler version: version 3.6.4-RC1-bin-SNAPSHOT-nonbootstrapped-git-164a8ed
            settings: -Ycheck List(all) -classpath /Users/jchyb/Library/Caches/Coursier/v1/https/repo1.maven.org/maven2/org/scala-lang/scala-library/2.13.15/scala-library-2.13.15.jar:/Users/jchyb/workspace/scala3/library/../out/bootstrap/scala3-library-bootstrapped/scala-3.6.4-RC1-bin-SNAPSHOT-nonbootstrapped/scala3-library_3-3.6.4-RC1-bin-SNAPSHOT.jar
        at scala.runtime.Scala3RunTime$.assertFailed(Scala3RunTime.scala:8)
        at dotty.tools.dotc.transform.Erasure.assertErased(Erasure.scala:202)
        at dotty.tools.dotc.transform.Erasure.assertErased(Erasure.scala:179)
        at dotty.tools.dotc.transform.Erasure.checkPostCondition(Erasure.scala:156)
        at dotty.tools.dotc.transform.TreeChecker$.dotty$tools$dotc$transform$TreeChecker$Checker$$_$typedUnadapted$$anonfun$1(TreeChecker.scala:439)
        at scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
        at scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
        at scala.collection.immutable.List.foreach(List.scala:334)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedUnadapted(TreeChecker.scala:439)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3659)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3663)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typed(TreeChecker.scala:416)
        at dotty.tools.dotc.typer.Typer.typedSeqLiteral(Typer.scala:2387)
        at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3519)
        at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3582)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedUnadapted(TreeChecker.scala:434)
        at dotty.tools.dotc.typer.ProtoTypes$FunProto.$anonfun$7(ProtoTypes.scala:543)
        at dotty.tools.dotc.typer.ProtoTypes$FunProto.cacheTypedArg(ProtoTypes.scala:466)
        at dotty.tools.dotc.typer.ProtoTypes$FunProto.typedArg(ProtoTypes.scala:544)
        at dotty.tools.dotc.typer.Applications$ApplyToUntyped.typedArg(Applications.scala:1007)
        at dotty.tools.dotc.typer.Applications$ApplyToUntyped.typedArg(Applications.scala:1007)
        at dotty.tools.dotc.typer.Applications$Application.addTyped$1(Applications.scala:688)
        at dotty.tools.dotc.typer.Applications$Application.matchArgs(Applications.scala:756)
        at dotty.tools.dotc.typer.Applications$Application.init(Applications.scala:574)
        at dotty.tools.dotc.typer.Applications$TypedApply.<init>(Applications.scala:882)
        at dotty.tools.dotc.typer.Applications$ApplyToUntyped.<init>(Applications.scala:1006)
        at dotty.tools.dotc.typer.Applications.ApplyTo(Applications.scala:1270)
        at dotty.tools.dotc.typer.Applications.ApplyTo$(Applications.scala:434)
        at dotty.tools.dotc.typer.Typer.ApplyTo(Typer.scala:148)
        at dotty.tools.dotc.typer.Applications.simpleApply$1(Applications.scala:1079)
        at dotty.tools.dotc.typer.Applications.realApply$1$$anonfun$2(Applications.scala:1189)
        at dotty.tools.dotc.typer.Typer$.tryEither(Typer.scala:121)
        at dotty.tools.dotc.typer.Applications.realApply$1(Applications.scala:1204)
        at dotty.tools.dotc.typer.Applications.typedApply(Applications.scala:1244)
        at dotty.tools.dotc.typer.Applications.typedApply$(Applications.scala:434)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedApply(TreeChecker.scala:543)
        at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3497)
        at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3582)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedUnadapted(TreeChecker.scala:434)
        at dotty.tools.dotc.typer.ProtoTypes$FunProto.$anonfun$7(ProtoTypes.scala:543)
        at dotty.tools.dotc.typer.ProtoTypes$FunProto.cacheTypedArg(ProtoTypes.scala:466)
        at dotty.tools.dotc.typer.ProtoTypes$FunProto.typedArg(ProtoTypes.scala:544)
        at dotty.tools.dotc.typer.Applications$ApplyToUntyped.typedArg(Applications.scala:1007)
        at dotty.tools.dotc.typer.Applications$ApplyToUntyped.typedArg(Applications.scala:1007)
        at dotty.tools.dotc.typer.Applications$Application.addTyped$1(Applications.scala:688)
        at dotty.tools.dotc.typer.Applications$Application.matchArgs(Applications.scala:756)
        at dotty.tools.dotc.typer.Applications$Application.init(Applications.scala:574)
        at dotty.tools.dotc.typer.Applications$TypedApply.<init>(Applications.scala:882)
        at dotty.tools.dotc.typer.Applications$ApplyToUntyped.<init>(Applications.scala:1006)
        at dotty.tools.dotc.typer.Applications.ApplyTo(Applications.scala:1270)
        at dotty.tools.dotc.typer.Applications.ApplyTo$(Applications.scala:434)
        at dotty.tools.dotc.typer.Typer.ApplyTo(Typer.scala:148)
        at dotty.tools.dotc.typer.Applications.simpleApply$1(Applications.scala:1079)
        at dotty.tools.dotc.typer.Applications.realApply$1$$anonfun$2(Applications.scala:1189)
        at dotty.tools.dotc.typer.Typer$.tryEither(Typer.scala:121)
        at dotty.tools.dotc.typer.Applications.realApply$1(Applications.scala:1204)
        at dotty.tools.dotc.typer.Applications.typedApply(Applications.scala:1244)
        at dotty.tools.dotc.typer.Applications.typedApply$(Applications.scala:434)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedApply(TreeChecker.scala:543)
        at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3497)
        at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3582)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedUnadapted(TreeChecker.scala:434)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3659)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3663)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typed(TreeChecker.scala:416)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedTyped(TreeChecker.scala:563)
        at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3502)
        at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3582)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedUnadapted(TreeChecker.scala:434)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3659)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3663)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typed(TreeChecker.scala:416)
        at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:3712)
        at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:3731)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedStats(TreeChecker.scala:691)
        at dotty.tools.dotc.typer.Typer.typedBlockStats(Typer.scala:1430)
        at dotty.tools.dotc.typer.Typer.typedBlock(Typer.scala:1434)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedBlock$$anonfun$1$$anonfun$1(TreeChecker.scala:673)
        at dotty.tools.dotc.transform.TreeChecker$Checker.withDefinedSyms(TreeChecker.scala:278)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedBlock$$anonfun$1(TreeChecker.scala:673)
        at dotty.tools.dotc.transform.TreeChecker$Checker.withBlock(TreeChecker.scala:306)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedBlock(TreeChecker.scala:673)
        at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3505)
        at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3582)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedUnadapted(TreeChecker.scala:434)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3659)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3663)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typed(TreeChecker.scala:416)
        at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:3774)
        at dotty.tools.dotc.typer.Typer.$anonfun$66(Typer.scala:2898)
        at dotty.tools.dotc.inlines.PrepareInlineable$.dropInlineIfError(PrepareInlineable.scala:256)
        at dotty.tools.dotc.typer.Typer.typedDefDef(Typer.scala:2898)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedDefDef$$anonfun$1(TreeChecker.scala:648)
        at dotty.tools.dotc.transform.TreeChecker$Checker.withDefinedSyms(TreeChecker.scala:278)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedDefDef(TreeChecker.scala:651)
        at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:3479)
        at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3581)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedUnadapted(TreeChecker.scala:434)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3659)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3663)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typed(TreeChecker.scala:416)
        at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:3685)
        at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:3731)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedStats(TreeChecker.scala:691)
        at dotty.tools.dotc.typer.Typer.typedClassDef(Typer.scala:3164)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedClassDef(TreeChecker.scala:618)
        at dotty.tools.dotc.typer.Typer.typedTypeOrClassDef$1(Typer.scala:3485)
        at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:3489)
        at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3581)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedUnadapted(TreeChecker.scala:434)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3659)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3663)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typed(TreeChecker.scala:416)
        at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:3685)
        at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:3731)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedStats(TreeChecker.scala:691)
        at dotty.tools.dotc.typer.Typer.typedPackageDef(Typer.scala:3297)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedPackageDef(TreeChecker.scala:717)
        at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3531)
        at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3582)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedUnadapted(TreeChecker.scala:434)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3659)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3663)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typed(TreeChecker.scala:416)
        at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:3774)
        at dotty.tools.dotc.transform.TreeChecker.check(TreeChecker.scala:131)
        at dotty.tools.dotc.transform.TreeChecker.run(TreeChecker.scala:111)
        at dotty.tools.dotc.core.Phases$Phase.runOn$$anonfun$1(Phases.scala:380)
        at scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
        at scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
        at scala.collection.immutable.List.foreach(List.scala:334)
        at dotty.tools.dotc.core.Phases$Phase.runOn(Phases.scala:373)
        at dotty.tools.dotc.Run.runPhases$1$$anonfun$1(Run.scala:343)
        at scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
        at scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
        at scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1323)
        at dotty.tools.dotc.Run.runPhases$1(Run.scala:336)
        at dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:383)
        at dotty.tools.dotc.Run.compileUnits$$anonfun$adapted$1(Run.scala:395)
        at dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:69)
        at dotty.tools.dotc.Run.compileUnits(Run.scala:395)
        at dotty.tools.dotc.Run.compileUnits(Run.scala:288)
        at dotty.tools.dotc.Run.compileSuspendedUnits(Run.scala:409)
        at dotty.tools.dotc.Driver.finish(Driver.scala:63)
        at dotty.tools.dotc.Driver.doCompile(Driver.scala:38)
        at dotty.tools.dotc.Driver.process(Driver.scala:201)
        at dotty.tools.dotc.Driver.process(Driver.scala:169)
        at dotty.tools.dotc.Driver.process(Driver.scala:181)
        at dotty.tools.dotc.Driver.main(Driver.scala:211)
        at dotty.tools.dotc.Main.main(Main.scala)

Expectation

No crash. Instead, an error message from -Xcheck-macros or -Ycheck:all. The issue here lies with an incorrect macro implementation causing the generated code to have a parameterless Array in an illegal spot. If this was a transparent inline macro, this would be caught and reported by a PostTyper check. Perhaps the best fix here is implementing a similar -Xcheck-macros check, however it in my opinion should be limited to just checking a correct Array construction. Otherwise it could cause regressions in the ecosystem (as far I could see, other parameterless type constructors will not cause crashes like this anyway).

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