[GHC] #7939: RHS of associated type not kind-checked

[GHC]

#7939: RHS of associated type not kind-checked
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  Reporter:  goldfire                     |          Owner:                  
      Type:  bug                          |         Status:  new             
  Priority:  normal                       |      Milestone:                  
 Component:  Compiler                     |        Version:  7.7             
Resolution:                               |       Keywords:                  
        Os:  Unknown/Multiple             |   Architecture:  Unknown/Multiple
   Failure:  GHC accepts invalid program  |     Difficulty:  Unknown         
  Testcase:  ghci/scripts/T7939           |      Blockedby:                  
  Blocking:                               |        Related:                  
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Comment(by monoidal):

 Aha - `type Bar a` in a typeclass declaration defaults to `type Bar a ::
 k`, while `type family Baz a` defaults to `type family Baz a :: *`. This
 is a slight inconsistency.

 Meanwhile, we can also write

 {{{
 {-# LANGUAGE TypeFamilies, PolyKinds #-}
 type family A :: k
 type instance A = Double
 type instance A = Maybe
 }}}

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7939#comment:5>
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