What you're saying doesn't make sense to me, and I also don't know what you're referring to by the leaking problem. I don't see how the choice of being explicit

What you're saying doesn't make sense to me, and I also don't know what you're referring to by the leaking problem. I don't see how the choice of being explicit or non-explicit about errors is "faulty." Plenty of languages choose to use exceptions and maximize your ability to ignore errors, while others force you to deal with (in some way) the fact that an operation is fallible. Neither of these is "wrong," in my opinion, but they do offer different tradeoffs and ergonomics. I'm not sure why you say that the values of a sum type must be "dependent," or what you mean by that. Maybe/Option is a sum type of Nothing or Some<T>. There's no dependency there. If my webserver can return JSON or XML, I might represent that with a sum type holding either a JSON object or an XML tree, but there's no dependency between those two things that I can see.