A locally defined scala.Enumeration blows up at runtime

[dwijnand]

Minimized code

class Foo {
  implicit class StringShould(private val s: String) {
    def should(right: => Unit) = right
  }

  "Foo" should {
    object Weekdays extends Enumeration {
      val Mon, Tue, Wed, Thu, Fri, Sat, Sun = Value
    }
    println(Weekdays.Mon.toString)
  }
}

object Main {
  def main(args: Array[String]): Unit = new Foo()
}

Output

$ scala3 Foo.scala
Exception in thread "main" java.lang.IllegalAccessException: class scala.Enumeration cannot access a member of class Foo$Weekdays$1$ with modifiers "public"
	at java.base/jdk.internal.reflect.Reflection.newIllegalAccessException(Reflection.java:361)
	at java.base/java.lang.reflect.AccessibleObject.checkAccess(AccessibleObject.java:591)
	at java.base/java.lang.reflect.Method.invoke(Method.java:558)
	at scala.Enumeration.$anonfun$populateNameMap$3(Enumeration.scala:208)
	at scala.Enumeration.populateNameMap(Enumeration.scala:205)
	at scala.Enumeration.$anonfun$nameOf$1(Enumeration.scala:220)
	at scala.collection.mutable.HashMap.getOrElse(HashMap.scala:436)
	at scala.Enumeration.scala$Enumeration$$nameOf(Enumeration.scala:220)
	at scala.Enumeration$Val.toString(Enumeration.scala:263)
	at Foo.$init$$$anonfun$1(Foo.scala:10)
	at Foo$StringShould.should(Foo.scala:3)
	at Foo.<init>(Foo.scala:11)
	at Main$.main(Foo.scala:15)
	at Main.main(Foo.scala)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:566)
	at dotty.tools.scripting.ScriptingDriver.compileAndRun(ScriptingDriver.scala:29)
	at dotty.tools.scripting.Main$.main(Main.scala:18)
	at dotty.tools.scripting.Main.main(Main.scala)

Expectation

No runtime exception.

[griggt]

A slightly simpler example:

object Test {
  def main(args: Array[String]): Unit = {
    object Weekdays extends Enumeration {
      val Mon, Tue, Wed, Thu, Fri, Sat, Sun = Value
    }
    println(Weekdays.Mon.toString)
  }
}

Scala 2.13.4 sets the ACC_PUBLIC flag on the Test$Weekdays$1$ class, whereas 3.0.0-M3 does not:

Classfile /src/dotty-issues/i11052/2.13.4/Test$Weekdays$1$.class
  Last modified Jan 10, 2021; size 1240 bytes
  MD5 checksum f780afb1c834667f5acfb93297e8a279
  Compiled from "i11052.scala"
public class Test$Weekdays$1$ extends scala.Enumeration
  minor version: 0
  major version: 52
  flags: (0x0021) ACC_PUBLIC, ACC_SUPER

Classfile /src/dotty-issues/i11052/3.0.0-M3/Test$Weekdays$1$.class
  Last modified Jan 10, 2021; size 1100 bytes
  MD5 checksum f1fd7bc67fcbf80245a8d813cf917803
  Compiled from "i11052.scala"
final class Test$Weekdays$1$ extends scala.Enumeration
  minor version: 0
  major version: 52
  flags: (0x003a) ACC_FINAL, ACC_SUPER, 0x8, 0x2

[griggt]

Fixed by #14686