IllegalAccessError when Scala class invokes public super method from package private Java class

[lukaseder]

Compiler version

3.6.3

Minimized code

p/I.java

package p;

public interface I {
    String string();
}

p/A.java

package p;

abstract class A implements I {
    @Override
    public String string() {
        return "s";
    }
}

p/B.java

package p;

public class B extends A {
}

q/S.scala

package q

object S {
  def main(args: Array[String]): Unit = {
    println(new S().string())
  }
}

class S extends p.B {
  override def string(): String = super.string()
}

Then run:

scala p/I.java p/A.java p/B.java q/S.scala

Output

Exception in thread "main" java.lang.IllegalAccessError: failed to access class p.A from class q.S (p.A and q.S are in unnamed module of loader 'app')
        at q.S.string(S.scala:10)
        at q.S$.main(S.scala:5)
        at q.S.main(S.scala)

Expectation

This should run just like in Scala 2.13 and earlier, or with the following Java program:

package r;

public class S extends p.B {
    @Override
    public String string() {
        return super.string();
    }

    public static void main(String[] args) {
        System.out.println(new S().string());
    }
}

Workarounds

This can be prevented with an auxiliary override in p.B:

package p;

public class B extends A {
    @Override
    public String string() {
        return super.string();
    }
}

Or, of course, by making A public. Both may not be possible or reasonable, though. I don't really see a workaround on the client side (in q.S)

[lukaseder]

It reminds me of this past issue with the Scala 2 compiler:

• NullPointerException: Cannot invoke "scala.reflect.internal.Types$Type.typeSymbol()" because the return value of "scala.reflect.internal.Trees$Tree.tpe()" is null bug#12380 (comment)

[lukaseder]

Also:

• [java-interop] compiler error "Unable to access method in class with a super reference" when mixing java/scala inheritance bug#7936