TypeTest for opaque type with wildcard argument causes unresolved symbol error

[tschuchortdev]

Compiler version

3.3.3

Minimized code

import scala.reflect.TypeTest
object Foo {
  opaque type Opaque[T] = Option[T]
  def newOpaque[T]: Opaque[T] = Option.empty[T]

  given [T]: TypeTest[Any, Opaque[T]] with {
     override def unapply(x: Any): Option[x.type & Opaque[T]] = Option.empty[x.type & Opaque[T]]
  }
}

def bar(o: Any) = o match
  case b: Foo.Opaque[?] => println("match opaque wildcard")
  case _ => println("NO match opaque wildcard")

import scala.reflect.TypeTest
object Foo2 {
  opaque type Opaque[F[_]] = Option[F[Unit]]
  def newOpaque[F[_]]: Opaque[F] = Option.empty[F[Unit]]

  given [F[_]]: TypeTest[Any, Opaque[F]] with {
     override def unapply(x: Any): Option[x.type & Opaque[F]] = Option.empty[x.type & Opaque[F]]
  }
}

def bar2(o: Any) = o match
  case b: Foo2.Opaque[? <: [_] =>> Any] => println("match opaque wildcard")
  case _ => println("NO match opaque wildcard")

Output (click arrow to expand)

Both examples crash with java.lang.AssertionError: assertion failed: unresolved symbols: type _ (line 72) #122346 when pickling. In the second example, if we write Foo2.Opaque[?] instead, it will compile, but only because the wildcard type is of the wrong kind ? >: Nothing <: Any, which can not legally be applied as an argument here, so that the TypeTest is never chosen by the compiler.

[error] java.lang.AssertionError: assertion failed: unresolved symbols: type _ (line 72) #122346 when pickling /Users/thilo/Documents/hkd-playground/src/main/scala/Main.scala
[error] scala.runtime.Scala3RunTime$.assertFailed(Scala3RunTime.scala:8)
[error] dotty.tools.dotc.core.tasty.TreePickler.pickle(TreePickler.scala:829)
[error] dotty.tools.dotc.transform.Pickler.run$$anonfun$1$$anonfun$1(Pickler.scala:90)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
[error] scala.collection.immutable.List.foreach(List.scala:333)
[error] dotty.tools.dotc.transform.Pickler.run$$anonfun$1(Pickler.scala:143)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
[error] scala.collection.immutable.List.foreach(List.scala:333)
[error] dotty.tools.dotc.transform.Pickler.run(Pickler.scala:143)
[error] dotty.tools.dotc.core.Phases$Phase.runOn$$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.transform.Pickler.runOn(Pickler.scala:151)
[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$$anonfun$adapted$1(Run.scala:279)
[error] dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:71)
[error] dotty.tools.dotc.Run.compileUnits(Run.scala:279)
[error] dotty.tools.dotc.Run.compileUnits(Run.scala:200)
[error] dotty.tools.dotc.Driver.finish(Driver.scala:58)
[error] dotty.tools.dotc.Driver.doCompile(Driver.scala:38)
[error] dotty.tools.xsbt.CompilerBridgeDriver.run(CompilerBridgeDriver.java:136)
[error] dotty.tools.xsbt.CompilerBridge.run(CompilerBridge.java:22)
[error] sbt.internal.inc.AnalyzingCompiler.compile(AnalyzingCompiler.scala:91)
[error] sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$7(MixedAnalyzingCompiler.scala:193)
[error] scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:23)
[error] sbt.internal.inc.MixedAnalyzingCompiler.timed(MixedAnalyzingCompiler.scala:248)
[error] sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$4(MixedAnalyzingCompiler.scala:183)
[error] sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$4$adapted(MixedAnalyzingCompiler.scala:163)
[error] sbt.internal.inc.JarUtils$.withPreviousJar(JarUtils.scala:239)
[error] sbt.internal.inc.MixedAnalyzingCompiler.compileScala$1(MixedAnalyzingCompiler.scala:163)
[error] sbt.internal.inc.MixedAnalyzingCompiler.compile(MixedAnalyzingCompiler.scala:211)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1(IncrementalCompilerImpl.scala:534)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1$adapted(IncrementalCompilerImpl.scala:534)
[error] sbt.internal.inc.Incremental$.$anonfun$apply$5(Incremental.scala:180)
[error] sbt.internal.inc.Incremental$.$anonfun$apply$5$adapted(Incremental.scala:178)
[error] sbt.internal.inc.Incremental$$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$2.call(CompletionService.scala:65)
[error] java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
[error] java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515)
[error] java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
[error] java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
[error] java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
[error] java.base/java.lang.Thread.run(Thread.java:834)
[error]            
[error] stack trace is suppressed; run last Compile / compileIncremental for the full output
[error] (Compile / compileIncremental) java.lang.AssertionError: assertion failed: unresolved symbols: type _ (line 72) #122346 when pickling /Users/thilo/Documents/hkd-playground/src/main/scala/Main.scala

(line numbers may not be accurate as I copied the example from a different file)

Also see #20430.

[Gedochao]

Added a missing import scala.reflect.TypeTest in the reproduction code in the original post.
Full crash output:

unhandled exception while running pickler on /Users/pchabelski/IdeaProjects/scala-cli-tests/compiler-repro/repro.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 -Yno-enrich-error-messages.

     while compiling: /Users/pchabelski/IdeaProjects/scala-cli-tests/compiler-repro/repro.scala
        during phase: pickler
                mode: Mode(ImplicitsEnabled)
     library version: version 2.13.12
    compiler version: version 3.4.2
            settings: -classpath /Users/pchabelski/Library/Caches/Coursier/v1/https/repo1.maven.org/maven2/org/scala-lang/scala3-library_3/3.4.2/scala3-library_3-3.4.2.jar:/Users/pchabelski/Library/Caches/Coursier/v1/https/repo1.maven.org/maven2/org/scala-lang/scala-library/2.13.12/scala-library-2.13.12.jar -d /Users/pchabelski/IdeaProjects/scala-cli-tests/compiler-repro/.scala-build/compiler-repro_b24481f081-fb1e690db3/classes/main -java-output-version 17 -sourceroot /Users/pchabelski/IdeaProjects/scala-cli-tests/compiler-repro

Exception in thread "main" java.lang.AssertionError: assertion failed: unresolved symbols: type _ (line 12) #8734 when pickling /Users/pchabelski/IdeaProjects/scala-cli-tests/compiler-repro/repro.scala
        at scala.runtime.Scala3RunTime$.assertFailed(Scala3RunTime.scala:8)
        at dotty.tools.dotc.core.tasty.TreePickler.pickle(TreePickler.scala:872)
        at dotty.tools.dotc.transform.Pickler.run$$anonfun$1$$anonfun$1(Pickler.scala:136)
        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:333)
        at dotty.tools.dotc.transform.Pickler.run$$anonfun$1(Pickler.scala:194)
        at scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
        at scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
        at scala.collection.immutable.List.foreach(List.scala:333)
        at dotty.tools.dotc.transform.Pickler.run(Pickler.scala:194)
        at dotty.tools.dotc.core.Phases$Phase.runOn$$anonfun$1(Phases.scala:354)
        at scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
        at scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
        at scala.collection.immutable.List.foreach(List.scala:333)
        at dotty.tools.dotc.core.Phases$Phase.runOn(Phases.scala:360)
        at dotty.tools.dotc.transform.Pickler.runOn(Pickler.scala:211)
        at dotty.tools.dotc.Run.runPhases$1$$anonfun$1(Run.scala:315)
        at scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
        at scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
        at scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1323)
        at dotty.tools.dotc.Run.runPhases$1(Run.scala:337)
        at dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:350)
        at dotty.tools.dotc.Run.compileUnits$$anonfun$adapted$1(Run.scala:360)
        at dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:69)
        at dotty.tools.dotc.Run.compileUnits(Run.scala:360)
        at dotty.tools.dotc.Run.compileSources(Run.scala:261)
        at dotty.tools.dotc.Run.compile(Run.scala:246)
        at dotty.tools.dotc.Driver.doCompile(Driver.scala:37)
        at dotty.tools.dotc.Driver.process(Driver.scala:196)
        at dotty.tools.dotc.Driver.process(Driver.scala:164)
        at dotty.tools.dotc.Driver.process(Driver.scala:176)
        at dotty.tools.dotc.Driver.main(Driver.scala:206)
        at dotty.tools.dotc.Main.main(Main.scala)