I'm currently working out ideas for potential optimizations in pattern matching compilation for GHC. While I think the theory works out fine in regards to exceptions I would like feedback on the possible implications. Trac ticket with details is here: https://ghc.haskell.org/trac/ghc/ticket/14201#comment:4 As for the theory I worked based of the assumptions that error = bottom and pattern match failure = error. Otherwise we get different results from both cases even in theory. While I mostly worry about the practical implications I would also appreciate any other feedback.