[GHC] #10602: ghc panic: Template variable unbound in rewrite rule when compiling with -O2

[GHC]

#10602: ghc panic: Template variable unbound in rewrite rule when compiling with
-O2
-------------------------------------+-------------------------------------
              Reporter:  pacak       |             Owner:
                  Type:  bug         |            Status:  new
              Priority:  normal      |         Milestone:  7.10.2
             Component:  Compiler    |           Version:  7.10.2-rc2
              Keywords:              |  Operating System:  Linux
          Architecture:              |   Type of failure:  Compile-time
  Unknown/Multiple                   |  crash
             Test Case:              |        Blocked By:
              Blocking:              |   Related Tickets:
Differential Revisions:              |
-------------------------------------+-------------------------------------
 I've seen a few related tickets, but they are market as closed.


 % ghc -O2 binlist.hs


 [1 of 1] Compiling Main             ( binlist.hs, binlist.o )
 ghc: panic! (the 'impossible' happened)
   (GHC version 7.10.1.20150630 for x86_64-unknown-linux):
         Template variable unbound in rewrite rule
   sg_s5zh
   [sc_s5zf, sc_s5zg, sg_s5zh, sg_s5zi]
   [sc_s5zf, sc_s5zg, sg_s5zh, sg_s5zi]
   [: @ a_a3fo sc_s5zf sc_s5zg]
   [: @ a_a3fo sc_s5zb sc_s5zc]

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

 % cat binlist.hs
 import Control.Monad
 import Data.Binary
 import Data.List


 newtype A a = A [a]


 instance Binary a => Binary (A a) where
     put (A xs) = case splitAt 254 xs of
         (_, []) -> mapM_ put xs
         (a, b)  -> put (A b)

     get = do xs <- replicateM 254 get
              A ys <- get
              return $ A $ xs ++ ys

 main :: IO ()
 main = undefined

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10602>
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