id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	os	architecture	failure	difficulty	testcase	blockedby	blocking	related
5603	Impossible case alternative	igloo	simonpj	"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
}}}
"	bug	closed	highest	7.4.1	Compiler	7.3	fixed			Unknown/Multiple	Unknown/Multiple	None/Unknown		simplCore/should_run/T5603