[GHC] #13391: PolyKinds is more permissive in GHC 8

[GHC]

#13391: PolyKinds is more permissive in GHC 8
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        Reporter:  crockeea          |                Owner:  (none)
            Type:  bug               |               Status:  patch
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.2
      Resolution:                    |             Keywords:  TypeInType
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  GHC accepts       |  Unknown/Multiple
  invalid program                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D3859
       Wiki Page:                    |
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Comment (by bgamari):

 One non-obvious implication of this change is that program like the
 `KindEqualities` test from the testsuite will now require that users
 enable `TypeInType` and consequently will manually need to quantify over
 the kind variables of their tycon's signature. For instance, currently
 `KindEqualities` has,
 {{{#!hs
 data TyRep :: k -> * where
   TyInt :: TyRep Int
   -- etc.
 }}}
 This needs to become,
 {{{#!hs
 data TyRep :: forall k. k -> * where
   TyInt :: TyRep Int
   -- etc.
 }}}
 This is documented in Phab:D3966.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13391#comment:7>
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