} else {
                    context.add(method, "Can only be one of " + describeHandlers());
                    validateRuleMethod(ruleDefinition, method, context);
                    return null;
                }
            }
        }
        if (handler != null) {
            validateRuleMethod(ruleDefinition, method, context);
            return handler.registration(ruleDefinition, context);
        } else {