I think I found the problem. package ghc-7.8.3 requires transformers-0.3.0.0 package mtl-2.2.1 requires transformers-0.4.1.0 package exceptions-0.6.1 requires transformers-0.4.1.0
I wonder how is this ever supposed to work :( On Sun, Jul 20, 2014 at 9:01 PM, Edward Z. Yang <ezy...@mit.edu> wrote: > The last time I saw this error, it was because the package database > was messed up (there was an instance of MonadIO in scope, but it > was for the wrong package.) However, I don't know what the source > of the problem is here. > > Edward > > Excerpts from i hamsa's message of 2014-07-20 08:26:52 +0100: >> I was trying to upgrade to ghc-7.8 the other day, and got this >> compilation failure when building ghc-mtl-1.2.1.0 (see the end of the >> message). >> >> I'm using the haskell overlay on Gentoo Linux straight out of the box, >> no local cabal installations of anything. >> >> Now I was told that other people can compile ghc-mtl with 7.8 just >> fine, so there must be something broken in my specific configuration. >> What would be an effective way to approach the situation? >> >> In the sources I see that an instance of MonadIO GHC.Ghc does exist. I >> don't understand these errors. Are there multiple different MonadIO >> classes in different modules? >> >> Thank you and happy hacking. >> >> Now the errors: >> >> Control/Monad/Ghc.hs:42:15: >> No instance for (GHC.MonadIO Ghc) >> arising from the 'deriving' clause of a data type declaration >> Possible fix: >> use a standalone 'deriving instance' declaration, >> so you can specify the instance context yourself >> When deriving the instance for (GHC.ExceptionMonad Ghc) >> >> Control/Monad/Ghc.hs:46:15: >> No instance for (MonadIO GHC.Ghc) >> arising from the 'deriving' clause of a data type declaration >> Possible fix: >> use a standalone 'deriving instance' declaration, >> so you can specify the instance context yourself >> When deriving the instance for (MonadIO Ghc) >> >> Control/Monad/Ghc.hs:49:15: >> No instance for (GHC.MonadIO Ghc) >> arising from the 'deriving' clause of a data type declaration >> Possible fix: >> use a standalone 'deriving instance' declaration, >> so you can specify the instance context yourself >> When deriving the instance for (GHC.GhcMonad Ghc) >> -- this is the real i _______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
