[GHC] #11719: Cannot use higher-rank kinds with type families

[GHC]

#11719: Cannot use higher-rank kinds with type families
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        Reporter:  ocharles          |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.8.1
       Component:  Compiler (Type    |              Version:  8.0.1-rc2
  checker)                           |
      Resolution:                    |             Keywords:  TypeInType
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  GHC rejects       |            Test Case:
  valid program                      |  dependent/should_compile/T11719
      Blocked By:                    |             Blocking:
 Related Tickets:  #13913            |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by goldfire):

 These two declarations have quite different meanings:

 {{{#!hs
 type family F1 :: k -> Type
 type family F2 :: forall k. k -> Type
 }}}

 `F1` takes one argument, `k`. `F2`, on the other hand, takes no arguments.
 `F1` can match on `k`, returning constructors of different kinds in
 different instances. On the other hand, `F2` must return a polykinded
 constructor, and can have only one instance.

 So, I think this is unrelated to the ticket...

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11719#comment:14>
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