add mypy to get warnings on unreachable code, fix/ignore various small typing errors

[jakkdl]

Didn't see an option to warn on unreachable code in pyright, and I tried running Vulture for that but that started requiring me to disable 90%+ of it since it doesn't detect that visitor/leave functions are run, and a lot of other weirdness. So I settled for running .. another type checker :partying_face: But disabled a couple error codes for now. It did give some decent warnings on eval files though:

• 103: changing if statements' test from True to ... makes it clearer that the test isn't evaluated
• 104: infinite loops at module level turned off type checking (see #155 )
• 105: noreturn calls have to be split out to get type checking

It does feel silly to run double type checkers, but I'm progressively realizing that linting the h*ck out of the eval files is actually useful - despite how irritating it can be.

[Zac-HD]

I'm progressively realizing that linting the h*ck out of the eval files is actually useful - despite how irritating it can be.

Oooh, yes. One of the few things more annoying than a really strict linter is realizing that you should have started using one a while ago!

[jakkdl]

haha! so true, so true