[GHC] #7238: class methods with associated equality constraints panic

[GHC]

#7238: class methods with associated equality constraints panic
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 Reporter:  dmwit               |          Owner:                
     Type:  bug                 |         Status:  new           
 Priority:  normal              |      Component:  Compiler      
  Version:  7.6.1               |       Keywords:                
       Os:  Linux               |   Architecture:  x86_64 (amd64)
  Failure:  Compile-time crash  |       Testcase:                
Blockedby:                      |       Blocking:                
  Related:                      |  
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 The following file causes a panic ("getEqPredTys"):

 {{{
 {-# LANGUAGE ConstraintKinds, TypeFamilies #-}
 import GHC.Exts

 class Pair p where
         type Ctxt p a :: Constraint
         l :: Ctxt p a => p a -> a

 data Unit a = Unit

 instance Pair Unit where
         type Ctxt Unit a = a ~ ()
         l _ = ()
 }}}

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7238>
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