Exception when trying to run a class expression

[anatoliykmetyuk]

minimized code

Macro:

package playground

import scala.quoted._, scala.quoted.matching._
import delegate scala.quoted._
import scala.tasty._

delegate for Toolbox = Toolbox.make(getClass.getClassLoader)

object macros {
  inline def mcr(x: => Any): Any = ${mcrImpl('x)}

  class Foo { val x = 10 }

  def mcrImpl(body: Expr[Any]) given (ctx: QuoteContext): Expr[Any] = {
    import ctx.tasty._
    body match {
      case '{$x: Foo} => run(x).x.toExpr
    }
  }
}

Main:

package playground

import playground.macros._

val foo = new Foo
@main def main = println(mcr { foo })

Error

Error while emitting <quoted.Expr>
[error] -- Error: /Users/anatolii/Projects/dotty/playground/core/src/main/scala/playground/Main.scala:6:29
[error] 6 |@main def main = println(mcr { foo })
[error]   |                         ^^^^^^^^^^^
[error]   |Exception occurred while executing macro expansion.
[error]   |java.lang.AssertionError: assertion failed: Bad superClass for class Any: val <none>
[error]   |	at dotty.DottyPredef$.assertFail(DottyPredef.scala:16)
[error]   |	at dotty.tools.backend.jvm.BTypesFromSymbols.setClassInfo(BTypesFromSymbols.scala:66)
[error]   |	at dotty.tools.backend.jvm.BTypesFromSymbols.classBTypeFromSymbol$$anonfun$4(BTypesFromSymbols.scala:60)
[error]   |	at scala.collection.MapLike.getOrElse(MapLike.scala:131)
[error]   |	at scala.collection.MapLike.getOrElse$(MapLike.scala:129)
[error]   |	at scala.collection.AbstractMap.getOrElse(Map.scala:63)
[error]   |	at dotty.tools.backend.jvm.BTypesFromSymbols.classBTypeFromSymbol(BTypesFromSymbols.scala:61)
[error]   |	at dotty.tools.backend.jvm.BTypesFromSymbols.setClassInfo(BTypesFromSymbols.scala:77)
[error]   |	at dotty.tools.backend.jvm.BTypesFromSymbols.classBTypeFromSymbol$$anonfun$4(BTypesFromSymbols.scala:60)
[error]   |	at scala.collection.MapLike.getOrElse(MapLike.scala:131)
[error]   |	at scala.collection.MapLike.getOrElse$(MapLike.scala:129)
[error]   |	at scala.collection.AbstractMap.getOrElse(Map.scala:63)
[error]   |	at dotty.tools.backend.jvm.BTypesFromSymbols.classBTypeFromSymbol(BTypesFromSymbols.scala:61)
[error]   |	at dotty.tools.backend.jvm.BTypesFromSymbols.setClassInfo(BTypesFromSymbols.scala:77)
[error]   |	at dotty.tools.backend.jvm.BTypesFromSymbols.classBTypeFromSymbol$$anonfun$4(BTypesFromSymbols.scala:60)
[error]   |	at scala.collection.MapLike.getOrElse(MapLike.scala:131)
[error]   |	at scala.collection.MapLike.getOrElse$(MapLike.scala:129)
[error]   |	at scala.collection.AbstractMap.getOrElse(Map.scala:63)
[error]   |	at dotty.tools.backend.jvm.BTypesFromSymbols.classBTypeFromSymbol(BTypesFromSymbols.scala:61)
[error]   |	at dotty.tools.backend.jvm.BCodeHelpers$BCInnerClassGen.getClassBTypeAndRegisterInnerClass(BCodeHelpers.scala:238)
[error]   |	at dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.getClassBTypeAndRegisterInnerClass(BCodeSkelBuilder.scala:43)
[error]   |	at dotty.tools.backend.jvm.DottyBackendInterface.dotty$tools$backend$jvm$DottyBackendInterface$$anon$9$$_$primitiveOrClassToBType$3$$anonfun$3(DottyBackendInterface.scala:899)
[error]   |	at scala.collection.MapLike.getOrElse(MapLike.scala:131)
[error]   |	at scala.collection.MapLike.getOrElse$(MapLike.scala:129)
[error]   |	at scala.collection.AbstractMap.getOrElse(Map.scala:63)
[error]   |	at dotty.tools.backend.jvm.DottyBackendInterface$$anon$9.primitiveOrClassToBType$1(DottyBackendInterface.scala:899)
[error]   |	at dotty.tools.backend.jvm.DottyBackendInterface$$anon$9.toTypeKind(DottyBackendInterface.scala:918)
[error]   |	at dotty.tools.backend.jvm.BCodeHelpers$BCInnerClassGen.toTypeKind(BCodeHelpers.scala:267)
[error]   |	at dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.toTypeKind(BCodeSkelBuilder.scala:43)
[error]   |	at dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.tpeTK(BCodeSkelBuilder.scala:75)
[error]   |	at dotty.tools.backend.jvm.BCodeBodyBuilder$PlainBodyBuilder.genTypeApply(BCodeBodyBuilder.scala:639)
[error]   |	at dotty.tools.backend.jvm.BCodeBodyBuilder$PlainBodyBuilder.genLoad(BCodeBodyBuilder.scala:430)
[error]   |	at dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.emitNormalMethodBody$1(BCodeSkelBuilder.scala:597)
[error]   |	at dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.genDefDef(BCodeSkelBuilder.scala:630)
[error]   |	at dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.gen(BCodeSkelBuilder.scala:501)
[error]   |	at dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.gen$$anonfun$1(BCodeSkelBuilder.scala:503)
[error]   |	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:15)
[error]   |	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:10)
[error]   |	at scala.collection.immutable.List.foreach(List.scala:392)
[error]   |	at dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.gen(BCodeSkelBuilder.scala:503)
[error]   |	at dotty.tools.backend.jvm.BCodeSkelBuilder$PlainSkelBuilder.genPlainClass(BCodeSkelBuilder.scala:109)
[error]   |	at dotty.tools.backend.jvm.GenBCodePipeline$Worker1.visit(GenBCode.scala:218)
[error]   |	at dotty.tools.backend.jvm.GenBCodePipeline$Worker1.run(GenBCode.scala:185)
[error]   |	at dotty.tools.backend.jvm.GenBCodePipeline.buildAndSendToDisk(GenBCode.scala:515)
[error]   |	at dotty.tools.backend.jvm.GenBCodePipeline.run(GenBCode.scala:481)
[error]   |	at dotty.tools.backend.jvm.GenBCode.run(GenBCode.scala:54)
[error]   |	at dotty.tools.dotc.core.Phases$Phase.runOn$$anonfun$1(Phases.scala:316)
[error]   |	at scala.collection.immutable.List.map(List.scala:286)
[error]   |	at dotty.tools.dotc.core.Phases$Phase.runOn(Phases.scala:318)
[error]   |	at dotty.tools.backend.jvm.GenBCode.runOn(GenBCode.scala:59)
[error]   |	at dotty.tools.dotc.Run.runPhases$4$$anonfun$4(Run.scala:158)
[error]   |	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:15)
[error]   |	at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:10)
[error]   |	at scala.collection.IndexedSeqOptimized.foreach(IndexedSeqOptimized.scala:36)
[error]   |	at scala.collection.IndexedSeqOptimized.foreach$(IndexedSeqOptimized.scala:33)
[error]   |	at scala.collection.mutable.ArrayOps$ofRef.foreach(ArrayOps.scala:198)
[error]   |	at dotty.tools.dotc.Run.runPhases$5(Run.scala:170)
[error]   |	at dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:178)
[error]   |	at dotty.runtime.function.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:12)
[error]   |	at dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:65)
[error]   |	at dotty.tools.dotc.Run.compileUnits(Run.scala:185)
[error]   |	at dotty.tools.dotc.Run.compileUnits(Run.scala:125)
[error]   |	at dotty.tools.dotc.quoted.QuoteCompiler$ExprRun.compileExpr(QuoteCompiler.scala:102)
[error]   |	at dotty.tools.dotc.quoted.QuoteDriver.run(QuoteDriver.scala:36)
[error]   |	at dotty.tools.dotc.quoted.ToolboxImpl$$anon$1.run(ToolboxImpl.scala:19)
[error]   |	at scala.quoted.package$.run(package.scala:21)
[error]   |	at playground.macros$.mcrImpl(macros.scala:17)
[error]   |
[error]   | This location is in code that was inlined at Main.scala:6
[error] one error found

expectation

I'd expect to be able to run any expression, given that there are mechanisms in place to ensure their self-consistency (phase consistency principle). If for some reason it is not possible to run expressions of classes, I'd expect a more user-friendly error.

[nicolasstucki]

Here we have a scope extrusion of x, which should be rejected or have a better exception message. This is related to #4730.

[anatoliykmetyuk]

Do you think it is not possible to do run on some expressions? What's the cause?

[nicolasstucki]

Because you are trying to precompile code and run that depends on code that has not be compiled yet. It is even worse if you depend on a locally defined value.