Hi >> | These have always distressed me. Would it be feasible to refactor so >> | that this isn't necessary, e.g. >> | >> | typecheck :: HsSyn Name () -> HsSyn Name PostTcInfo
> The problem is that these annotations tend to be constructor-specific. You > might get it to work with GADTs, but I'm not convinced > that would be easier to use. You don't have to track this information in the type system. You could rewrite: type PostTcType = Maybe Type Now you're representing the data that isn't there by a Nothing, rather than a _|_. You could even newtype it and have fromPostTcType be equivalent to fromJust with a helpful error about the ordering. It will be slower than what's currently there, but also more accurate statement of intent. > This causes problems when defining generic traversals over this syntax tree > (e.g., using SYB). There is no easy type-based > way of skipping over such values. Partly a warning, partly a plug - you might want to try Uniplate instead of SYB, it's likely to be at least 3 times faster even if you just layer it on top of the SYB/Data instances. I also feel that if you start to "tweak" the data instances, you'll quickly run in to problems - but maybe not. Thanks, Neil _______________________________________________ Cvs-ghc mailing list Cvs-ghc@haskell.org http://www.haskell.org/mailman/listinfo/cvs-ghc
