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

27 May 2013

      #7939: RHS of associated type not kind-checked
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Reporter:  goldfire                     |          Owner:  goldfire        
    Type:  bug                          |         Status:  new             
Priority:  normal                       |      Component:  Compiler        
 Version:  7.7                          |       Keywords:                  
      Os:  Unknown/Multiple             |   Architecture:  Unknown/Multiple
 Failure:  GHC accepts invalid program  |      Blockedby:                  
Blocking:                               |        Related:                  
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 The following code compiles without complaint:

 {{{
 {-# LANGUAGE TypeFamilies, PolyKinds #-}

 class Foo a where
   type Bar a

 instance Foo Int where
   type Bar Int = Maybe

 instance Foo Bool where
   type Bar Bool = Double
 }}}

 We can see here that {{{Bar}}} is ill-kinded. When I try {{{:k Bar}}} in
 GHCi, I get an assertion failure, not unexpectedly.

 I will fix in ongoing work.

-- 
Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7939
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