Your example is a good argument for using null or empty list in situations where that is applicable, but it doesn't explain why a custom error object or callbac

Your example is a good argument for using null or empty list in situations where that is applicable, but it doesn't explain why a custom error object or callback would be better than using an exception, even in reconcilable scenarios. In fact I think using a custom error object would go against your general point of taking advantage of preexisting language features where possible.