Add Haddock highlighting

[johntyree]

I swiped some highlighting tricks from my old syntax/haskell.vim file. This particular group adds highlighting of Haddock docs as SpecialComments

[raichoo]

Stupid question. What benefits does this have? I thought SpecialComment was meant to be for things like pragmas? I'd personally prefer to have Pragmas stand out, once you have a lot of haddock in your code pragmas kind of fade to the background a little bit too much for my taste.

[johntyree]

There is a highlight group called "PreProc" that is used for C pragmas. I would think haddock is very the definition of a "special comment," as it is literally a comment with special meaning in some contexts.

If you have a lot of haddock and find it distracting, you might rather choose a less intense color, but personally I like it to stand out. If I find myself needing to refer to comments frequently to be able to understand and use my code, it is helpful to have a visual reminder that the doc-comments really should be exported.

It also helps identify places where I'm accidentally not writing haddock when I meant to, which is usually a silent error.

[johntyree]

Hmmm... it looks like I'm not even use this anywhere. Must be vestigial. If you decide after all that this is worth pulling, I'll remove it.

[raichoo]

I recall that I made the pragmas SpecialComment because ghc-mod is using this group to complete Language extensions and pragmas alike. Slipped my mind.

[johntyree]

Oh! Good to know...

Patching that is a much bigger pain...

[NickHu]

Is there any hope that this will be merged?