TreeFormatter formatter = new TreeFormatter();
            formatter.node("Cannot have abstract method ");
            formatter.appendMethod(method);
            formatter.append(".");
            throw new IllegalArgumentException(formatter.toString());
        }

        append("@" + type.getSimpleName());
        return this;
    }

    /**
     * Appends a method name to the current node.
     */
    public TreeFormatter appendMethod(Method method) {
        // Implementation is currently dumb, can be made smarter
        append(method.getDeclaringClass().getSimpleName());
        append(".");
        append(method.getName());