[GHC] #14645: Allow type family in data family return kind

[GHC]

#14645: Allow type family in data family return kind
-------------------------------------+-------------------------------------
        Reporter:  goldfire          |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.4.1-alpha1
      Resolution:                    |             Keywords:  TypeInType,
                                     |  TypeFamilies
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by goldfire):

 > Does that look right?

 Almost. You need a cast in the type of `$WT1`:

 {{{#!hs
 $WT1 :: forall a. a -> (DF Bool |> ax1) a
 }}}

 Otherwise, yes, I agree.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14645#comment:4>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler