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.