Implement Maybe/Result with the built-in enum construct

[gaku-sei]

Both Maybe and Result are implemented using the free JS construct: https://github.com/mint-lang/mint/blob/master/core/source/Maybe.mint#L4

The problem is, it's impossible to "pattern match" them:

case (maybeNumber) {
  Maybe::Nothing => ...
  Maybe::Just number => ...
}

Would lead to an error stating the Maybe enum doesn't exist.

Even though it's extremely easy to use Maybe.map and Maybe.withDefault to achieve this, it feels a bit inconsistent, and might be confusing for the newcomers (especially those with a accustomed to functional programming).

NB: Sorry for posting a lot of issues, I really like the language, and hope it can be better and better!

[gdotdesign]

Maybe and Result are implemented this way because at the time there was no enum in the system 😄 so you are right and I'm planning to replace them with enums.

It's probably a nice exercise for someone to implement this 😉

• Implement Maybe and Result using enums (tests in core should pass)
• Replace every instance of new Just, new Nothing, new Ok, new Err with interpolations in the core *.mint files (tests in core should pass)
• Always typecheck Maybe and mark them to always compile (I think Result is only needed when used while Maybe is used internally)
• Replace every instance of new Just, new Nothing, new Ok, new Err in *.cr files by using their constructors (which is mangled)

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NB: Sorry for posting a lot of issues, I really like the language, and hope it can be better and better!

No worries! Most of them I had in my head for a while but didn't create an issue for it so this is good 👍