On Fri, Jan 20, 2012 at 6:52 AM, Michael Snoyman <mich...@snoyman.com> wrote: > On Fri, Jan 20, 2012 at 6:41 AM, Edward Z. Yang <ezy...@mit.edu> wrote: >> Aw, that is really suboptimal. Have you filed a bug? > > I think it's a feature, not a bug. When dealing with monads that > provide nice[1] implementations of `fail`, you can (ab)use this to > avoid writing a bunch of case expressions. I remember reading it in > one of the first tutorials on Haskell I looked at (four years ago now? > you can see how much this bothered me if I still remember that). > > I admit that there are some use cases where the current behavior is > convenient, but I think we're paying too steep a price. If we got rid > of this feature entirely, we could (a) get rid of fail and (b) have > the compiler warn us about a bunch of errors at compile time. > > But maybe I should file a feature request: provide an extra warning > flag (turned on by -Wall) that will warn when you match on a failable > pattern. Essentially, I would want: > > SomeConstr args <- someAction > > to be interpreted as: > > temp <- someAction > case temp of > SomeConstr args -> > > Michael
I've filed a feature request for this warning: http://hackage.haskell.org/trac/ghc/ticket/5813 Michael _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
