[Haddock] Data family instance documentation

[C Rodrigues]

Hi,


I have started adding data family instance support to haddock, since I have been wanting this feature.  So far, I've managed to show data instance definitions in HTML.  Until I implement the visibility computation, instances won't always show up when they should.  Since data instances are exported like class instances, but have bodies like data declarations, my plan is to show:


* Family instances are, like type classes, always exported.  They are listed as instances of their family.
* Family constructors are visible if they are exported.  If any constructors of a data family instance are visible, the instance is shown like a data definition in its home module. 

The GHC API is rather formidable.  I would like help with understanding two things.  What data structures in the API can I access to find type family instances and constructors?  How does the current Haddock code connect data constructors with data types (classDataSubs?). 

-Chris