[redirecting to ghc users] Actually this didn't work in 6.4.2 either! (Though it did in 6.4, for reasons I have not investigated.) Indeed I think your reasoning is correct. GHC tries to be pretty relaxed about reporting ambiguous types, which is what this amounts to really. I have committed a fix to the HEAD that relaxes the condition, and allows this program. It should appear in 6.6.1 also. Thanks for the report Simon | -----Original Message----- | From: haskell-bounces@haskell.org [mailto:haskell-bounces@haskell.org] | On Behalf Of dpus | Sent: 12 November 2006 19:36 | To: haskell@haskell.org | Subject: [Haskell] Fundep broken in GHC 6.6 | | Hi, | | The following class declaration worked in GHC 6.4. | I recently upgraded to 6.6 (following Debian), and | now it is broken. | | class Error e => Game b mv e | b -> mv e where | newBoard :: MonadState b m => m () | ... | | Since MonadState has the fundep m -> b, the type | of newBoard fully specifies all of the class parameters. | And this worked fine in GHC 6.4. But GHC 6.6 | complains: | | The class method `newBoard' | mentions none of the type variables of the class Game b mv e | When checking the class method: newBoard :: m () | In the class declaration for `Game' | | Any ideas? | | Thanks, | Yitz | _______________________________________________ | Haskell mailing list | Haskell@haskell.org | http://www.haskell.org/mailman/listinfo/haskell