On Fri, 2 Jan 2015, Roman Cheplyaka wrote: > I don't think it does. The first pattern (a:as) will be refuted, and the > second (b:bs) won't try to match at all. right - stupid me Then, the new behavior of zipWith is really a bug. I added a ticket: https://ghc.haskell.org/trac/ghc/ticket/9949