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module OpaqueNoRebox where
f :: (Int,Int) -> Int
f (x,y) = x + y
{-# OPAQUE f #-}
-- No W/W happens for f because it is OPAQUE, and by design its Boxity
-- information is stripped, which is good!
--
-- If we hadn't stripped the boxity information, we would make a worker
-- for g that would just rebox its arguments:
--
-- $wg :: Int# -> Int# -> Int
-- $wg ww ww1 =
-- let x = I# ww in
-- let y = I# ww1 in
-- let p = (x,y) in
-- case f (f p, f p) of { I# z -> ww +# z}
--
-- as $wg was expecting that a worker for f that would be inlined.
--
-- See Note [The OPAQUE pragma and avoiding the reboxing of arguments]
g :: (Int, Int) -> Int
g p = fst p + f (f p, f p)
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