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Simon Peyton Jones authored
Note [Case of cast] ~~~~~~~~~~~~~~~~~~~ Consider case (v `cast` co) of x { I# -> ... (case (v `cast` co) of {...}) ... We'd like to eliminate the inner case. We can get this neatly by arranging that inside the outer case we add the unfolding v |-> x `cast` (sym co) to v. Then we should inline v at the inner case, cancel the casts, and away we go This patch does the job, fixing a performance hole reported by Roman.
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