Scala: Overriding Generic Java Methods II

In Scala, I need to override the following, given, Java classes and methods:

public abstract class AbstractJava<T> {
    protected abstract T test(Class<? extends T> clazz);
}

public class ConcreteJava extends AbstractJava<Object> {
    @Override
    protected Object test(Class<?> clazz) {
        return null;
    }
}

// Scala
class ConcreteScala extends ConcreteJava {
    protected override def test(clazz: Class[_ <: AnyRef]): AnyRef =
        super.test(clazz)
}

I'm getting the compilation error:

error: ambiguous reference to overloaded definition,

both method test in class ConcreteJava of type 
(clazz: java.lang.Class[_])java.lang.Object

and method test in class AbstractJava of type 
(clazz: java.lang.Class[_ <: java.lang.Object])java.lang.Object

match argument types (Class[_$1]) and expected result type AnyRef

super.test(clazz)

I wouldn't expect the Scala compiler to refer to an abstract method on a super call. Also, I'd expect it to refer to the direct super class first.

How can I make the Scala class compile?

Thanks!

Edit:

When leaving off the super.test(clazz) call, there'll be the error message:

error: name clash between defined and inherited member:

method test:(clazz: Class[_ <: AnyRef])AnyRef and
method test:(clazz: java.lang.Class[_])java.lang.Object in class ConcreteJava

have same type after erasure: (clazz: java.lang.Class)java.lang.Object

protected override def test(clazz: Class[_ <: AnyRef]): AnyRef = null

Well, of course these are the same types (or variants) ...! - So there's something wrong with Scala/Java inheritance ...

Thanks to michid, there's a preliminary solution:

class ConcreteScala3 {
  this: ConcreteJava =>
  protected override def test(clazz: Class[_ <: AnyRef]): AnyRef = {
    this.foo() // method of ConcreteJava
    null
  }
}

although we can't make super calls from here.

Responses are still most welcome.

Scala: Overriding Generic Java Methods II

2 Answers