Encoding Either as a product `(a, error)` instead of a sum `a | error` is a pretty big difference. It becomes even sillier when you have to also signal "not fo

Encoding Either as a product `(a, error)` instead of a sum `a | error` is a pretty big difference. It becomes even sillier when you have to also signal "not found" with something like `(a, bool, error)` instead of `Found a | NotFound | Error error`