[GHC] #13687: GHC internal error: associated type not in scope during typechecking

11 May 2017


      #13687: GHC internal error: associated type not in scope during typechecking
-------------------------------------+-------------------------------------
           Reporter:  mrkgnao        |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.0.1
  (Type checker)                     |
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  Compile-time
  Unknown/Multiple                   |  crash or panic
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 From a larger snippet of code:

 {{{#!hs
 type family Strategy' a b n where
   Strategy' a b Zero = St a b -- this is where the error occurs
   Strategy' a b (Succ n)
     = Strategy' a b n
    <| ReverseArgs (Strategy' b a n)
    <| Combine (Strategy' a a n) (Strategy' b b n)

 class DefinedStrategy a b where
   type St
 }}}

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Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13687
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