Hi John,

I ran into it on 7.8.2, the solution was to install aeson, free and lens (in
this order). This is due to the fact that:

>  This is related to the recent update of transformers. If you could wait a few
>  days until the packages depending on transformers are upgraded, you shouldn't
>  run into any issues installing lens.

Source: http://stackoverflow.com/questions/23510242/cabal-dependency-resolution-fail-for-lens

Cheers,
Mateusz

On Mon, May 12, 2014 at 12:29:19AM +1000, John Ky wrote:
> Hi Haskell Cafe,
>
> Anyone know about this error?
>
> Installing library in
> /Users/johnky/Library/Haskell/ghc-7.6.3/lib/reflection-1.4/lib
> Registering reflection-1.4...
> Installed reflection-1.4
> Configuring mtl-2.0.1.0...
> Building mtl-2.0.1.0...
> Preprocessing library mtl-2.0.1.0...
> [ 1 of 21] Compiling Control.Monad.Writer.Class (
> Control/Monad/Writer/Class.hs, dist/build/Control/Monad/Writer/Class.o )
> [ 2 of 21] Compiling Control.Monad.State.Class (
> Control/Monad/State/Class.hs, dist/build/Control/Monad/State/Class.o )
> [ 3 of 21] Compiling Control.Monad.Reader.Class (
> Control/Monad/Reader/Class.hs, dist/build/Control/Monad/Reader/Class.o )
> [ 4 of 21] Compiling Control.Monad.RWS.Class ( Control/Monad/RWS/Class.hs,
> dist/build/Control/Monad/RWS/Class.o )
> [ 5 of 21] Compiling Control.Monad.Identity ( Control/Monad/Identity.hs,
> dist/build/Control/Monad/Identity.o )
> [ 6 of 21] Compiling Control.Monad.Error.Class (
> Control/Monad/Error/Class.hs, dist/build/Control/Monad/Error/Class.o )
>
> Control/Monad/Error/Class.hs:93:18: Not in scope: `catch'
> Failed to install mtl-2.0.1.0
>
> Cheers,
>
> -John
>

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