[GHC] #8062: Panic "Lookup local fingerprint main:Main.main{v r6xE}"

[GHC]

#8062: Panic "Lookup local fingerprint main:Main.main{v r6xE}"
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        Reporter:  tommd         |            Owner:
            Type:  bug           |           Status:  closed
        Priority:  normal        |        Milestone:
       Component:  Compiler      |          Version:  7.6.3
      Resolution:  fixed         |         Keywords:
Operating System:  Linux         |     Architecture:  Unknown/Multiple
 Type of failure:  None/Unknown  |       Difficulty:  Unknown
       Test Case:                |       Blocked By:
        Blocking:                |  Related Tickets:
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Changes (by tommd):

 * status:  new => closed
 * resolution:   => fixed


Comment:

 This is fixed in head, though the error message is a bit odd.  For the
 curious, a working example is:


 {{{
 {-# LANGUAGE FlexibleInstances, MultiParamTypeClasses, TypeFamilies #-}

 main = do
     bench bar :: IO Int
     return ()

 -- Run the monad, applying the value
 bench :: Pr c -> IO c
 bench = undefined

 -- Protocol monad
 newtype Pr a = Pr a

 -- Shared
 newtype Cont a = Cont a

 type family S (m :: * -> *) :: * -> *
 type instance S Pr = Cont

 bar :: Pr (S Pr a)
 bar = undefined
 }}}

 I'll close the ticket now.  Thanks to emertens for working to build the
 example and test HEAD.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8062#comment:3>
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