[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 RyanGlScott):

 Replying to [comment:9 goldfire]:
 > Why do you think you need step 2? I think the existing code in
 `kcDataDefn` will do the right thing here.

 I'm not sure that I understand this comment. You're suggesting that GHC
 will do all of the steps outlined in comment:3 with only step 1?
 Experimental evidence suggests that this is not true, as trying an
 implementation with only step 1 panics when given the program in
 comment:3.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14645#comment:10>
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