#7237: CgCase fails with strict data/functions
------------------------------+---------------------------------------------
Reporter: jwlato | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler
Version: 7.6.1 | Keywords:
Os: Unknown/Multiple | Architecture: Unknown/Multiple
Failure: None/Unknown | Testcase:
Blockedby: | Blocking:
Related: |
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The following code results in a ghc panic when compiled with -O or above:
{{{
-- Test.hs
module Test where
import Data.List (foldl')
data SPair = SPair { pX, pY :: Double } deriving (Eq,Show)
data AList = AList
{ pairs :: [SPair] } deriving Show
rnf' :: AList -> ()
rnf' aList = foldl' (flip seq) () (pairs aList) `seq` ()
{- -- this works
rnf' :: AList -> ()
rnf' aList = foldl (flip seq) () (pairs aList) `seq` ()
-}
}}}
The resulting error is
{{{
$ ghc -O Test.hs
[1 of 1] Compiling Test ( Test.hs, Test.o )
ghc: panic! (the 'impossible' happened)
(GHC version 7.6.1 for x86_64-unknown-linux):
compiler/codeGen/CgCase.lhs:572:15-61: Irrefutable pattern failed
for pattern ((CoreSyn.DEFAULT,
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7237>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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