[GHC] #11611: ghc panics

[GHC]

#11611: ghc panics
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           Reporter:  Iceland_jack   |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.1
           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
 {-# LANGUAGE DataKinds, StandaloneDeriving, TypeOperators, GADTs,
 FlexibleInstances #-}

 data A a where
   A :: A (a:as) -> a -> A as

 deriving instance Show a => Show (A a)
 }}}

 gives

 {{{#!hs
 % ghci -ignore-dot-ghci Panic.hs
 GHCi, version 8.1.20160117: http://www.haskell.org/ghc/  :? for help
 [1 of 1] Compiling Main             ( Panic.hs, interpreted )
 ghc: panic! (the 'impossible' happened)
   (GHC version 8.1.20160117 for x86_64-unknown-linux):
         fvProv falls into a hole {a1aV}

 Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug

 >
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11611>
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