fix: type checking in for loops

[iamdefinitelyahuman]

What I did

• Fix a bug in the type checker preventing proper checks during for loops. This wasn't a critical issue, as any failure is still caught in parser.
• Improve how exception messages are handled during a failed type check in a for loop

How I did it

• The main issue was from an improperly indented return. Ooops.
• For the exception message, I'm tracking every exception raised during the iterative check. At the end, if they're all the same exception, I raise it instead of the more generic "could not determine type for i".

How to verify it

Run tests.

Cute Animal Picture

[fubuloubu]

fdor lol

[iamdefinitelyahuman]

fnord