CgCase fails with strict data/functions

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,

Trac metadata

Trac field	Value
Version	7.6.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
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