It looks like you will have to install old versions of mtl/exceptions which work on transformers-0.3.0.0, although undoubtedly the real problem is that GHC should update what version of transformers it is distributing.
Edawrd Excerpts from i hamsa's message of 2014-07-20 19:25:36 +0100: > 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) > >> > _______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
