i hamsa | 20 Jul 09:26 2014
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Failure compiling ghc-mtl with ghc-7.8.{2,3}

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
(Continue reading)

Edward Z. Yang | 20 Jul 20:01 2014
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Re: Failure compiling ghc-mtl with ghc-7.8.{2,3}

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
(Continue reading)

i hamsa | 20 Jul 20:25 2014
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Re: Failure compiling ghc-mtl with ghc-7.8.{2,3}

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 <ezyang <at> 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
(Continue reading)

Edward Z. Yang | 20 Jul 20:36 2014
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Re: Failure compiling ghc-mtl with ghc-7.8.{2,3}

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 <ezyang <at> 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,
(Continue reading)


Gmane