Indentation mode needs to be able to recover from parser errors

[arybczak]

If there is a parse error while trying to determine indentation (e.g. after pressing Enter), the mode completely breaks down. In the past it dropped to the beginning of the next line, currently the Enter key just stops working. This makes the whole mode unreliable to use.

My proposition is that it should be ensured that if the indentation breaks, the mode will still be more or less usable (at least that one is able to go to the next line) until it's able to work again (by getting out of the context it can't parse possibly, I'm not sure how it's implemented). As for the indentation level, I think the best course of action would be to just stay at the indentation level it's at when going to the next line (which is the right course of action the majority of time).

[Shimuuar]

Yes this major usability problem. IMO enter should insert newline if indenter fails. There are always some weird corner case or plain invalid haskell which will cause parser errors so haskell-mode should fall back on some simpler heuristic

[gracjan]

Closing in favor of #962.