[GHC] #5603: Impossible case alternative

[GHC]

#5603: Impossible case alternative
---------------------------------+------------------------------------------
    Reporter:  igloo             |        Owner:              
        Type:  bug               |       Status:  new         
    Priority:  highest           |    Milestone:  7.4.1       
   Component:  Compiler          |      Version:  7.3         
    Keywords:                    |     Testcase:              
   Blockedby:                    |   Difficulty:              
          Os:  Unknown/Multiple  |     Blocking:              
Architecture:  Unknown/Multiple  |      Failure:  None/Unknown
---------------------------------+------------------------------------------
 With `q.hs`:
 {{{
 {-# LANGUAGE MagicHash, UnboxedTuples, UnliftedFFITypes #-}

 module Main (main) where

 import GHC.Base
 import GHC.Integer.GMP.Internals

 main :: IO ()
 main = (encodeDouble 0 :: Double) `seq` return ()

 {-# INLINE encodeDouble #-}
 encodeDouble :: Integer -> Double
 encodeDouble (S# _)   = D# 3.0##
 encodeDouble (J# _ _) = D# 4.0##
 }}}
 with the HEAD I get:
 {{{
 $ ghc --make q -O -dcore-lint -dcmm-lint
 [1 of 1] Compiling Main             ( q.hs, q.o )
 Linking q ...
 $ ./q
 q: Impossible case alternative
 }}}

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5603>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler