mb_rat_lit = case (mb_neg, val) of
(Nothing, HsIntegral i) -> Just (fromInteger i)
(Just _, HsIntegral i) -> Just (fromInteger (-i))
mb_rat_lit = case (mb_neg, val) of
(Nothing, HsIntegral i) -> Just (fromInteger i)
(Just _, HsIntegral i) -> Just (fromInteger (-i))