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import System.Environment
import GHC.Exts
g :: (Int -> (Int, Int)) -> Int
-- Should *not* infer strictness SCS(P(SL,SL)) for h
-- Otherwise `main` could use CbV on the error exprs below
g h = fst (h 0) + snd (h 1)
{-# NOINLINE g #-}
main = do
m <- length <$> getArgs
-- The point here is that we print "1".
-- That means we may *not* use CbV/let-to-case on err!
-- GHC.Exts.lazy so that we don't lambda lift and float out the
-- obviously bottoming RHS (where it is no longer used strictly).
let err = GHC.Exts.lazy $ error (show m)
let f n | even n = (n+m, err)
| otherwise = (err, n+m)
print $! g f
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