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

[GHC]

#14645: Allow type family in data family return kind
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        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:                    |
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Comment (by goldfire):

 If this is fixed before #12564, then we might get #15905. See
 comment:10:ticket:15905. Tread carefully.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14645#comment:12>
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