Selectable + opaque types cause crash

[rcano]

Compiler version

3.1.3 as well as 3.2-nightly

Minimized code

object SelectableBreaks {
  object opaques {
    opaque type Struct = Int

    opaque type Pointer[S <: Struct] <: S = S
    object Pointer {
      implicit class PointerSelectable[S <: Struct](private val f: Pointer[S]) extends Selectable {
        def selectDynamic(name: String): Any = ???
        def applyDynamic(name: String)(): Any = ???
      }
      // extension [S <: Struct](f: Pointer[S]) {
      //   def selectDynamic(name: String): Any = ???
      //   def applyDynamic(name: String)(): Any = ???
      // }
    }
  }
  import opaques.*

  type Break = Struct {
    def boom(): Nothing
  }

  def makeBreak(): Pointer[Break] = ???

  makeBreak().boom() // <-- selecting boom() here crashes the compiler. Crashes happens whether it's select or apply dynamic.
}

Output (click arrow to expand)

exception occurred while compiling /tmp/proj/src/main/scala/proj/selectable-breaks.scala
java.lang.AssertionError: assertion failed: no owner from  <none>/ <none> in proj.SelectableBreaks.makeBreak().boom while compiling /tmp/proj/src/main/scala/proj/selectable-breaks.scala
 ## Exception when compiling 44 sources to /tmp/proj/target/scala-3.1.2/classes
 java.lang.AssertionError: assertion failed: no owner from  <none>/ <none> in proj.SelectableBreaks.makeBreak().boom
 scala.runtime.Scala3RunTime$.assertFailed(Scala3RunTime.scala:8)
 dotty.tools.dotc.transform.Erasure$Typer.typedSelect(Erasure.scala:698)
 dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:2779)
 dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2871)
 dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:121)
 dotty.tools.dotc.typer.Typer.typed(Typer.scala:2937)
 dotty.tools.dotc.typer.Typer.typed(Typer.scala:2941)
 dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:3057)
 dotty.tools.dotc.transform.Erasure$Typer.typedApply(Erasure.scala:814)
 dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:2809)
 dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2872)
 dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:121)
 dotty.tools.dotc.typer.Typer.typed(Typer.scala:2937)
 dotty.tools.dotc.typer.Typer.typed(Typer.scala:2941)
 dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:2990)
 dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:3013)
 dotty.tools.dotc.transform.Erasure$Typer.typedStats(Erasure.scala:1030)
 dotty.tools.dotc.typer.Typer.typedClassDef(Typer.scala:2454)
 dotty.tools.dotc.transform.Erasure$Typer.typedClassDef(Erasure.scala:1020)
 dotty.tools.dotc.typer.Typer.typedTypeOrClassDef$1(Typer.scala:2797)
 dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:2801)
 dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2871)
 dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:121)
 dotty.tools.dotc.typer.Typer.typed(Typer.scala:2937)
 dotty.tools.dotc.typer.Typer.typed(Typer.scala:2941)
 dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:2963)
 dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:3013)
 dotty.tools.dotc.transform.Erasure$Typer.typedStats(Erasure.scala:1030)
 dotty.tools.dotc.typer.Typer.typedPackageDef(Typer.scala:2581)
 dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:2842)
 dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2872)
 dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:121)
 dotty.tools.dotc.typer.Typer.typed(Typer.scala:2937)
 dotty.tools.dotc.typer.Typer.typed(Typer.scala:2941)
 dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:3057)
 dotty.tools.dotc.transform.Erasure.run(Erasure.scala:144)
 dotty.tools.dotc.core.Phases$Phase.runOn$$anonfun$1(Phases.scala:308)
 scala.collection.immutable.List.map(List.scala:246)
 dotty.tools.dotc.core.Phases$Phase.runOn(Phases.scala:309)
 dotty.tools.dotc.Run.runPhases$1$$anonfun$1(Run.scala:259)
 scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
 scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
 scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1328)
 dotty.tools.dotc.Run.runPhases$1(Run.scala:270)
 dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:278)
 scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.scala:18)
 dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:68)
 dotty.tools.dotc.Run.compileUnits(Run.scala:287)
 dotty.tools.dotc.Run.compileSources(Run.scala:220)
 dotty.tools.dotc.Run.compile(Run.scala:204)
 dotty.tools.dotc.Driver.doCompile(Driver.scala:39)
 dotty.tools.xsbt.CompilerBridgeDriver.run(CompilerBridgeDriver.java:88)
 dotty.tools.xsbt.CompilerBridge.run(CompilerBridge.java:22)
 sbt.internal.inc.AnalyzingCompiler.compile(AnalyzingCompiler.scala:91)
 sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$7(MixedAnalyzingCompiler.scala:192)
 scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:23)
 sbt.internal.inc.MixedAnalyzingCompiler.timed(MixedAnalyzingCompiler.scala:247)
 sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$4(MixedAnalyzingCompiler.scala:182)
 sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$4$adapted(MixedAnalyzingCompiler.scala:163)
 sbt.internal.inc.JarUtils$.withPreviousJar(JarUtils.scala:239)
 sbt.internal.inc.MixedAnalyzingCompiler.compileScala$1(MixedAnalyzingCompiler.scala:163)
 sbt.internal.inc.MixedAnalyzingCompiler.compile(MixedAnalyzingCompiler.scala:210)
 sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1(IncrementalCompilerImpl.scala:528)
 sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1$adapted(IncrementalCompilerImpl.scala:528)
 sbt.internal.inc.Incremental$.$anonfun$apply$5(Incremental.scala:177)
 sbt.internal.inc.Incremental$.$anonfun$apply$5$adapted(Incremental.scala:175)
 sbt.internal.inc.Incremental$$anon$2.run(Incremental.scala:461)
 sbt.internal.inc.IncrementalCommon$CycleState.next(IncrementalCommon.scala:116)
 sbt.internal.inc.IncrementalCommon$$anon$1.next(IncrementalCommon.scala:56)
 sbt.internal.inc.IncrementalCommon$$anon$1.next(IncrementalCommon.scala:52)
 sbt.internal.inc.IncrementalCommon.cycle(IncrementalCommon.scala:263)
 sbt.internal.inc.Incremental$.$anonfun$incrementalCompile$8(Incremental.scala:416)
 sbt.internal.inc.Incremental$.withClassfileManager(Incremental.scala:503)
 sbt.internal.inc.Incremental$.incrementalCompile(Incremental.scala:403)
 sbt.internal.inc.Incremental$.apply(Incremental.scala:169)
 sbt.internal.inc.IncrementalCompilerImpl.compileInternal(IncrementalCompilerImpl.scala:528)
 sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileIncrementally$1(IncrementalCompilerImpl.scala:482)
 sbt.internal.inc.IncrementalCompilerImpl.handleCompilationError(IncrementalCompilerImpl.scala:332)
 sbt.internal.inc.IncrementalCompilerImpl.compileIncrementally(IncrementalCompilerImpl.scala:420)
 sbt.internal.inc.IncrementalCompilerImpl.compile(IncrementalCompilerImpl.scala:137)
 sbt.Defaults$.compileIncrementalTaskImpl(Defaults.scala:2366)
 sbt.Defaults$.$anonfun$compileIncrementalTask$2(Defaults.scala:2316)
 sbt.internal.server.BspCompileTask$.$anonfun$compute$1(BspCompileTask.scala:30)
 sbt.internal.io.Retry$.apply(Retry.scala:46)
 sbt.internal.io.Retry$.apply(Retry.scala:28)
 sbt.internal.io.Retry$.apply(Retry.scala:23)
 sbt.internal.server.BspCompileTask$.compute(BspCompileTask.scala:30)
 sbt.Defaults$.$anonfun$compileIncrementalTask$1(Defaults.scala:2314)
 scala.Function1.$anonfun$compose$1(Function1.scala:49)
 sbt.internal.util.$tilde$greater.$anonfun$$u2219$1(TypeFunctions.scala:62)
 sbt.std.Transform$$anon$4.work(Transform.scala:68)
 sbt.Execute.$anonfun$submit$2(Execute.scala:282)
 sbt.internal.util.ErrorHandling$.wideConvert(ErrorHandling.scala:23)
 sbt.Execute.work(Execute.scala:291)
 sbt.Execute.$anonfun$submit$1(Execute.scala:282)
 sbt.ConcurrentRestrictions$$anon$4.$anonfun$submitValid$1(ConcurrentRestrictions.scala:265)
 sbt.CompletionService$$anon$2.call(CompletionService.scala:64)
 java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
 java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:539)
 java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
 java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136)
 java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
 java.base/java.lang.Thread.run(Thread.java:833)

Note: both options, with the implicit class or with extension methods (which is commented out) cause the same crash.

[KacperFKorban]

I managed to minimize it quite a bit. Turns out that it doesn't require opaque types nor Selectable.

type Pointer[S <: Int] <: S

type Break = Int {
  def boom: Unit
}

def test = {
  val ptrBreak: Pointer[Break] = ???
  ptrBreak.boom // boom crashes the compiler
}

[odersky]

@KacperFKorban Good minimization. I verified that it gets rejected with 80364f8.