| Thanks very much for this. I would never have guessed to use | -XRelaxedPolyRec given the error message. | | Is it worth noting it here | http://haskell.org/haskellwiki/Upgrading_packages#Changes_to_GADT_matching | or is it something that has always existed with GADTs and I just didn't | trip over it? I've added a para. Good idea. | > This is a nasty corner I agree. GHC requires -XGADTs for you to | > *define* a GADT. Perhaps it should also require -XGADTs for you to | > *match against* one (as you are doing here). That would avoid this | > particular hole. If you think that would be a step forward, do put | > forward a Trac feature request, and encourage others to support it. | | I would vote for this. In fact I was mildly surprised I could use GADTs | without specifying -XGADTs. | | I noticed that Isaac Dupree has already raised a ticket | http://permalink.gmane.org/gmane.comp.lang.haskell.glasgow.user/16109 so | I will add my support to it. OK. let's see if anyone else comments. Do ping me in a while to action it if I forget. Simon