[GHC] #15763: GHC forbids kind signatures in data family instances

[GHC]

#15763: GHC forbids kind signatures in data family instances
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        Reporter:  goldfire          |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.6.1
      Resolution:                    |             Keywords:
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):

 No. `data` is a declaration (binding site) and has its own, restrictive
 syntax. On the other hand, the head of a `data instance` is a type,
 containing only occurrences, not binding sites. (Even the type variables
 are occurrences. They are magically and invisibly bound by an implicit
 `forall`.)

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15763#comment:2>
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