During my (ongoing) vim experiment, I found myself missing some of the amenities of haskell-mode for emacs. Namely great syntax highlighting and pretty good indentation. vim2hs looked reasonably nice, but did not handle indentation. It also made scrolling very slow, perhaps because it just does too many fancy things. haskellmode-vim had slightly worse syntax highlighting and was also a bit slow; it also did not have much of an indentation story.
In response, I wrote hasksyn, which has both good syntax highlighting and pretty good indentation. Indentation is tricky in vim, I can appreciate that now, but I think I did a reasonable job.
- Align pipes, commas, and let bindings
- Indent after trailing operators,
case ... of
into match its corresponding
- De-indent after catchall cases and returns (optional)
Most importantly, comments and strings that happen to contain Haskell keywords will not confuse the indentation. I threw in a new cabal highlighting mode, too, because I got a bit annoyed that “keywords” were being highlighted in my package descriptions and module names.