AspectJ compiler bug leads to StackOverflowError

Question

I run into a StackOverflow error of the AspectJ compiler today and I thought I should share it on StackOverflow :-) To reproduce the error I made a toy example

public abstract class Node<T,Q extends Node<T,Q>> implements WithParent<Q>{
    private T content;
    //getter and setter for content
}
public aspect WithParentAspect {
    private T WithParent<T>.parent;
    public T WithParent<T>.getParent() {
        return this.parent;
    }
    public void WithParent<T>.setParent(T parent) {
        this.parent=parent;
    }
}
public interface WithParent<T> { }
public class StringContentNode extends Node<String, StringContentNode>{
    public static void main (String [] args) {
        StringContentNode root = new StringContentNode();
        StringContentNode leaf = new StringContentNode();

        root.setContent("root");
        leaf.setContent("leaf");
        leaf.setParent(root);
        System.out.println(leaf);                   
        System.out.println(leaf.getParent());
    }
}

Trying to compile this code results in the following error:

java.lang.StackOverflowError
at org.aspectj.weaver.World$TypeMap.put(World.java:1198)
at org.aspectj.weaver.World.resolve(World.java:398)
at org.aspectj.weaver.World.resolve(World.java:277)
at org.aspectj.weaver.World.resolve(World.java:229)
at org.aspectj.weaver.UnresolvedType.resolve(UnresolvedType.java:615)
at org.aspectj.weaver.ReferenceType.isAssignableFrom(ReferenceType.java:621)
at org.aspectj.weaver.ReferenceType.isAssignableFrom(Ref ...
bleFrom(ReferenceType.java:459)
at org.aspectj.weaver.TypeVariable.isASubtypeOf(TypeVariable.java:201)  

However, if I modify the Generics in the Node class to

public abstract class Node<T,Q extends Node<T,?>> implements WithParent<Q>{
...

(notice the ? instead of Q), the program works, and prints what you would expect:

Node (content=leaf, parent=Node (content=root, parent=null))
Node (content=root, parent=null)

even though Eclipse complains that

The method setParent(StringContentNode) is undefined for the type StringContentNode

if I leave the WithParent Interface empty as is now, or that

The type StringContentNode must implement the inherited abstract method WithParent.getParent()

If I define the getter and the setter in the interface.
Should I signal the bug? Is there a cleaner way to achieve the same functionality, without incurring in any weird compilation issue? Thanks!

Answer 1

It seems no one will propose a workaround that allows to keep implementing recursive generics interfaces through AspectJ in spite of the bug. It would have been interesting to find such a solution but I guess it is not likely to exist.

Please cast your votes on the bug report https://bugs.eclipse.org/bugs/show_bug.cgi?id=526707 if you can.

Cheers.

---

update: according to Tim Wright the bug is fixed in version 1.9.5 of aspectjrt