Help understanding a dependency conflict

Antoine Latter aslatter at
Fri Jan 7 22:23:48 CET 2011

On Fri, Jan 7, 2011 at 1:56 PM, tsuraan <tsuraan at> wrote:
> I have a program that's using both json (0.4.4) and hslogger (1.1.0).
> During the "cabal configure" stage of compiling my program, I get this
> error message:
> Warning: This package indirectly depends on multiple versions of the same
> package. This is highly likely to cause a compile failure.
> package json-0.4.4 requires mtl-
> package hslogger-1.1.0 requires mtl-
> Looking at the .cabal files for json and hslogger, they both have
> dependencies on "mtl", but neither package gives a version for it.  I
> only have mtl installed, so installing json didn't bring in an
> old version of the library when it was installed.  My program compiles
> and runs without any errors.  Can anybody tell my why cabal thinks
> json needs mtl, and what I can do to make the message go away?

Is there a reason you need to make the warning go away?

Maybe your installed version of parsec is built against mtl-1 - parsec
is a dependency of json.


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