Good point. Error message improved, regression test added. Thanks for the suggestion
Simon | -----Original Message----- | From: Dean Herington [mailto:[EMAIL PROTECTED]] | Sent: 05 February 2003 19:14 | To: [EMAIL PROTECTED] | Subject: confusing error message | | buzzard(118)% cat Bug5.hs | import Control.Monad.State | data S = S Int | newtype M a = M (StateT S IO a) | deriving (Monad) | | main = return () | buzzard(119)% ghc -c Bug5.hs | | Bug5.hs:3: | Can't make a derived instance of `Monad M' | (too hard for cunning newtype deriving) | When deriving instances for type `M' | buzzard(120)% ghc --version | The Glorious Glasgow Haskell Compilation System, version 5.04.2 | | | The real problem above is that I forgot to enable extensions. It would | be helpful if the error message indicated that as the problem. | | | _______________________________________________ | Glasgow-haskell-bugs mailing list | [EMAIL PROTECTED] | http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs _______________________________________________ Glasgow-haskell-bugs mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
