Hi Simon, Thanks. So there was a bug in the type checker. Do you have a link to the ticket or commits which fixed the issue?
Mitsutoshi 2014-12-30 19:56 GMT+09:00 Simon Peyton Jones <simo...@microsoft.com>: > UndecidableInstances is supposed to be needed if GHC can’t prove that the > instance declarations terminate. But here it can be sure they terminate. > GHC 7.6.3 didn’t realise this. > > > > I’ll modify the user manual to be clearer on this point. > > > > Simon > > > > From: Glasgow-haskell-users > [mailto:glasgow-haskell-users-boun...@haskell.org] On Behalf Of Mitsutoshi > Aoe > Sent: 28 December 2014 10:47 > To: glasgow-haskell-users@haskell.org > Subject: Changes to the type checker with respect to UndecidableInstances > > > > Hi, > > > > I found a difference between GHC 7.6.3 and 7.8.3 with respect to > UndecidableInstances. > > > > https://gist.github.com/maoe/57a4346eb36aee159916 > > > > 7.6.3 requires UndecidableInstances to compile this snippet whereas 7.8.3 > doesn't. What has changed in the type checker? > > > > Mitsutoshi > > _______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users