Hoogle backend oddities with type families

[RyanGlScott]

Take this file:

{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE UndecidableInstances #-}
module Bug where

import Data.Proxy

-- | 'F' docs
type family F
-- | 'D' docs
data family D

v :: Int
v = 42

-- | 'C' docs
class C a where
  -- | 'AT' docs
  type AT a
  type AT a = Proxy (Proxy (Proxy (Proxy (Proxy (Proxy (Proxy (Proxy (Proxy (Proxy)))))))))

And run haddock --hoogle --package-name=bug --package-version=0.0.0 Bug.hs, you'll get the following bug.txt file:

-- Hoogle documentation, generated by Haddock
-- See Hoogle, http://www.haskell.org/hoogle/

@package bug
@version 0.0.0

module Bug

-- | <a>F</a> docs

-- | <a>D</a> docs
v :: Int

-- | <a>C</a> docs
class C a where {
    type family AT a;
    type AT a =
        Proxy (Proxy (Proxy (Proxy (Proxy (Proxy (Proxy (Proxy (Proxy (Proxy)))))))));
}

There are many things wrong here:

1. Neither F nor D show up at all! This causes v to have a completely incorrect docstring associated with it.
2. AT does show up, but it's missing its Haddocks.
3. The default definition for AT spans multiple lines. According to @ndmitchell (in Search doesn't find top-level type families ndmitchell/hoogle#249 (comment)), this should never happen, as Hoogle is line-orientated.

[RyanGlScott]

For the life of me, I can't figure out how to fix part (3). But parts (1) and (2) are straightforward enough—see #808.

[alexbiehl]

3. Seems to be related to pretty printing, right? Shouldn't we be able to influence line breaking there?

[RyanGlScott]

(3) was fixed in #868.