[GHC] #12947: Core lint error

[GHC]

#12947: Core lint error
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           Reporter:  Iceland_jack   |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.0.1
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 {{{#!hs
 import qualified Control.Monad.Fail as Fail

 newtype P m a = P { unP :: (a -> IO (m ())) -> IO (m ()) }

 instance Functor (P m) where

 instance Applicative (P m) where

 instance Monad (P m) where

 instance (Fail.MonadFail m) => Fail.MonadFail (P m) where
   fail msg = ContT $ \ _ -> Fail.fail msg
 }}}

 fails when run with `$ ghci -ignore-dot-ghci -fdefer-typed-holes -dcore-
 lint /tmp/tQZR.hs`, log is attached

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12947>
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