Crash when referencing nested class in macro

[Katrix]

Compiler version

3.3.3

Minimized code

import scala.deriving.Mirror
import scala.quoted.{Expr, Quotes, Type}

trait macroTest[A] {
  type ElemTop <: A
  type Index[_]

  case class IdxWrapper[X](idx: Index[X])

  def indexOf[X <: ElemTop: Type](x: Expr[X]): Expr[Index[X]]

  def indexOfA(a: Expr[A]): Expr[IdxWrapper[_ <: ElemTop]]
}
object macroTest {

  def derivedImpl[A: Type, ElemTypes <: Tuple: Type, Label <: String: Type, Labels <: Tuple: Type](
      using m: Expr[
        Mirror.SumOf[A] {
          type MirroredElemTypes  = ElemTypes
          type MirroredLabel      = Label
          type MirroredElemLabels = Labels
        }
      ],
      q: Quotes,
  ): macroTest[A] = new macroTest[A]:
    override type Index[_] = Int

    // Also a problem in older versions of the compiler
    override def indexOf[X <: ElemTop: Type](x: Expr[X]): Expr[Index[X]] = '{ $m.ordinal($x) }

    // Commenting out the body of this function makes the code compile
    override def indexOfA(a: Expr[A]): Expr[IdxWrapper[_ <: ElemTop]] =
      given Type[IdxWrapper] = Type.of[IdxWrapper]
      given Type[ElemTop] = Type.of[ElemTop]
      '{ new IdxWrapper(${ indexOf(a.asInstanceOf[Expr[ElemTop]]) }) }
}

Output (click arrow to expand)

[error] ## Exception when compiling 10 sources to D:\DevProjects\Stable\perspective\dotty\derivation\.jvm\target\scala-3.3.3\classes
[error] java.lang.AssertionError: assertion failed: unresolved symbols: anonymous class Object with perspective.derivation.macroTest[A] {...} (line 26) #10766 when pickling D:\DevProjects\Stable\perspective\dotty\derivation\src\main\scala\perspective\derivation\macroTest.scala
[error] scala.runtime.Scala3RunTime$.assertFailed(Scala3RunTime.scala:8)
[error] dotty.tools.dotc.core.tasty.TreePickler.pickle(TreePickler.scala:829)
[error] dotty.tools.dotc.quoted.PickledQuotes$.pickle(PickledQuotes.scala:221)
[error] dotty.tools.dotc.quoted.PickledQuotes$.pickleQuote(PickledQuotes.scala:33)
[error] dotty.tools.dotc.transform.PickleQuotes$.pickleAsTasty$1(PickleQuotes.scala:308)
[error] dotty.tools.dotc.transform.PickleQuotes$.pickle(PickleQuotes.scala:392)
[error] dotty.tools.dotc.transform.PickleQuotes$$anon$1.transform(PickleQuotes.scala:99)
[error] dotty.tools.dotc.ast.tpd$TreeMapWithPreciseStatContexts.transformBlock$$anonfun$1$$anonfun$1(tpd.scala:1249)
[error] dotty.tools.dotc.ast.tpd$TreeMapWithPreciseStatContexts.loop$2(tpd.scala:1231)
[error] dotty.tools.dotc.ast.tpd$TreeMapWithPreciseStatContexts.transformStats(tpd.scala:1244)
[error] dotty.tools.dotc.ast.tpd$TreeMapWithPreciseStatContexts.transformBlock(tpd.scala:1249)
[error] dotty.tools.dotc.ast.Trees$Instance$TreeMap.transform(Trees.scala:1521)
[error] dotty.tools.dotc.transform.MacroTransform$Transformer.transform(MacroTransform.scala:49)
[error] dotty.tools.dotc.transform.PickleQuotes$$anon$1.transform(PickleQuotes.scala:103)
[error] dotty.tools.dotc.ast.Trees$Instance$TreeMap.transform(Trees.scala:1573)
[error] dotty.tools.dotc.transform.MacroTransform$Transformer.transform(MacroTransform.scala:40)
[error] dotty.tools.dotc.transform.PickleQuotes$$anon$1.transform(PickleQuotes.scala:103)
[error] dotty.tools.dotc.ast.tpd$TreeMapWithPreciseStatContexts.loop$2(tpd.scala:1244)
[error] dotty.tools.dotc.ast.tpd$TreeMapWithPreciseStatContexts.transformStats(tpd.scala:1244)
[error] dotty.tools.dotc.ast.tpd$TreeMapWithPreciseStatContexts.transformStats(tpd.scala:1246)
[error] dotty.tools.dotc.transform.MacroTransform$Transformer.transform(MacroTransform.scala:47)
[error] dotty.tools.dotc.transform.PickleQuotes$$anon$1.transform(PickleQuotes.scala:103)
[error] dotty.tools.dotc.ast.Trees$Instance$TreeMap.transform(Trees.scala:1575)
[error] dotty.tools.dotc.transform.MacroTransform$Transformer.transform(MacroTransform.scala:40)
[error] dotty.tools.dotc.transform.PickleQuotes$$anon$1.transform(PickleQuotes.scala:103)
[error] dotty.tools.dotc.ast.tpd$TreeMapWithPreciseStatContexts.loop$2(tpd.scala:1244)
[error] dotty.tools.dotc.ast.tpd$TreeMapWithPreciseStatContexts.transformStats(tpd.scala:1244)
[error] dotty.tools.dotc.ast.tpd$TreeMapWithPreciseStatContexts.transformBlock(tpd.scala:1249)
[error] dotty.tools.dotc.ast.Trees$Instance$TreeMap.transform(Trees.scala:1521)
[error] dotty.tools.dotc.transform.MacroTransform$Transformer.transform(MacroTransform.scala:49)
[error] dotty.tools.dotc.transform.PickleQuotes$$anon$1.transform(PickleQuotes.scala:103)
[error] dotty.tools.dotc.ast.Trees$Instance$TreeMap.transform(Trees.scala:1573)
[error] dotty.tools.dotc.transform.MacroTransform$Transformer.transform(MacroTransform.scala:40)
[error] dotty.tools.dotc.transform.PickleQuotes$$anon$1.transform(PickleQuotes.scala:103)
[error] dotty.tools.dotc.ast.tpd$TreeMapWithPreciseStatContexts.loop$2(tpd.scala:1244)
[error] dotty.tools.dotc.ast.tpd$TreeMapWithPreciseStatContexts.transformStats(tpd.scala:1244)
[error] dotty.tools.dotc.ast.tpd$TreeMapWithPreciseStatContexts.transformStats(tpd.scala:1246)
[error] dotty.tools.dotc.transform.MacroTransform$Transformer.transform(MacroTransform.scala:47)
[error] dotty.tools.dotc.transform.PickleQuotes$$anon$1.transform(PickleQuotes.scala:103)
[error] dotty.tools.dotc.ast.Trees$Instance$TreeMap.transform(Trees.scala:1575)
[error] dotty.tools.dotc.transform.MacroTransform$Transformer.transform(MacroTransform.scala:40)
[error] dotty.tools.dotc.transform.PickleQuotes$$anon$1.transform(PickleQuotes.scala:103)
[error] dotty.tools.dotc.ast.tpd$TreeMapWithPreciseStatContexts.loop$2(tpd.scala:1244)
[error] dotty.tools.dotc.ast.tpd$TreeMapWithPreciseStatContexts.transformStats(tpd.scala:1244)
[error] dotty.tools.dotc.ast.tpd$TreeMapWithPreciseStatContexts.transformStats(tpd.scala:1246)
[error] dotty.tools.dotc.ast.Trees$Instance$TreeMap.transform(Trees.scala:1586)
[error] dotty.tools.dotc.transform.MacroTransform$Transformer.transform(MacroTransform.scala:40)
[error] dotty.tools.dotc.transform.PickleQuotes$$anon$1.transform(PickleQuotes.scala:103)
[error] dotty.tools.dotc.transform.MacroTransform.run(MacroTransform.scala:18)
[error] dotty.tools.dotc.transform.PickleQuotes.run(PickleQuotes.scala:90)
[error] dotty.tools.dotc.core.Phases$Phase.runOn$$anonfun$1(Phases.scala:327)
[error] scala.collection.immutable.List.map(List.scala:246)
[error] dotty.tools.dotc.core.Phases$Phase.runOn(Phases.scala:331)
[error] dotty.tools.dotc.Run.runPhases$1$$anonfun$1(Run.scala:246)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
[error] scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1323)
[error] dotty.tools.dotc.Run.runPhases$1(Run.scala:262)
[error] dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:270)
[error] dotty.tools.dotc.Run.compileUnits$$anonfun$adapted$1(Run.scala:279)
[error] dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:71)
[error] dotty.tools.dotc.Run.compileUnits(Run.scala:279)
[error] dotty.tools.dotc.Run.compileSources(Run.scala:194)
[error] dotty.tools.dotc.Run.compile(Run.scala:179)
[error] dotty.tools.dotc.Driver.doCompile(Driver.scala:37)
[error] dotty.tools.xsbt.CompilerBridgeDriver.run(CompilerBridgeDriver.java:136)
[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)

[nicolasstucki]

Mimimization

import scala.quoted.*

def test(using Quotes): Any =
  new {
    class IdxWrapper
    def foo(using Type[IdxWrapper]): Expr[Any] = '{ new IdxWrapper }
  }

[nicolasstucki]

[[syntax trees at end of                   staging]] // t/Test.scala
package <empty> {
  import scala.quoted.*
  final lazy module val Test$package: Test$package = new Test$package()
  @SourceFile("t/Test.scala") final module class Test$package() extends Object()
     { this: Test$package.type =>
    private def writeReplace(): AnyRef =
      new scala.runtime.ModuleSerializationProxy(classOf[Test$package.type])
    def test(using x$1: scala.quoted.Quotes): Any =
      {
        final class $anon() extends Object() {
          class IdxWrapper() extends Object() {}
          def foo(using x$1: scala.quoted.Type[IdxWrapper]):
            scala.quoted.Expr[Any] = '<x$1>{new x$1.Underlying()}.apply(x$1)
        }
        new $anon():Object
      }
  }
}

Here '<x$1>{new x$1.Underlying()} the staging phase is trying to heal the reference to the type IdxWrapped inside the new. This will now work for references to local classes.

[nicolasstucki]

-- Error: t/Test.scala:6:32 ----------------------------------------------------
6 |    def foo: Expr[Any] = '{ new IdxWrapper }
  |                                ^^^^^^^^^^
  |Reference to IdxWrapper within quotes requires a given scala.quoted.Type[IdxWrapper] in scope.

This error message is also wrong. It should say that we cannot refer to a local class in a quote.

[Katrix]

Hmm, moving IdxWrapper to a static context I can do fairly easily to work around this, but is there any workarounds for local abstract types?

ElemTop is the thing I am thinking of here, though the bounds on the type type ElemTop <: A and the bounds on X in def indexOf[X <: ElemTop] I get a function that accepts all subtypes of A except A itself. Is there any recommended workarounds for working with abstract types like that in macros without a lof of nasty casting?

(For context, having a value of type Index[A] is unsound)