[GHC] #14042: Data type with type family in return kind spuriously rejected

[GHC]

#14042: Data type with type family in return kind spuriously rejected
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        Reporter:  RyanGlScott       |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.0.1
  checker)                           |             Keywords:  TypeInType,
      Resolution:                    |  TypeFamilies
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  GHC rejects       |  Unknown/Multiple
  valid program                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by simonpj):

 There are other places where we don't accept a type-function application;
 e.g.
 {{{
 type instance F Int = Bool

 instance C (F Int) where ...
 }}}
 And rightly so.

 This one is, I grant you, less justifiable.  But I think it'd be fiddly to
 support, and the motivation seems weak.  After all, data families always
 have result kind `*` so why not say so?

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14042#comment:1>
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