Remove haskell-checkers.el

[gracjan]

haskell-checkers used to provide:

• 'scan' interface (limited), as far as we know nobody is using that
• 'hlint' interface, superseeded by much better flycheck-hlint in flycheck project

[ivan-m]

I don't know about "much better": I still tend to prefer the hs-lint package that's shipped with hlint as it can update the errors for you (which I don't think flycheck can do); I see that haskell-checkers also has support for doing this kind of update.

[gracjan]

I guess nobody knew that haskell-checkers has this functionality (only for hlint). Haskell Mode should strive to provide Complete functionality.

Flycheck is moving in the direction described in flycheck/flycheck#530.

Proposition:

• you keep using the external package for now
• community helps flycheck to provide the functionality

I do not think we can afford keeping unused haskell-checkers around knowing that there are better options cooking elsewhere.

[ivan-m]

I did a quick search on GitHub, and it seems that those people who - like myself - require haskell-checkers aren't using it (I think the template .emacs setup for haskell-mode had it at one stage even though it wasn't used, so a few of us copy-pasted it in).

Possibly document the option of getting hs-lint more clearly for people who might want that functionality, especially since it seems flycheck won't be getting it any time soon.

[bbatsov]

Removing this makes sense.