Help understanding a dependency conflict

[tsuraan]

>> Is there some way to have cabal (or some other ghc packaging program)
>> tell me about dependencies, and what packages have brought in what
>> other packages?  I can't imagine that digging through .cabal files is
>> the normal way to figure this out.
>
> ghc-pkg describe yourpackage

Much more sane.  "ghc-pkg describe json" lists mtl-1.1.0.2, but none
of the other deps (array, base, bytestring, containers, parsec,
pretty, syb) depend on mtl at all.  It's especially strange that when
I installed json through cabal it didn't have any problem using mtl-2,
but now it's decided json wants mtl-1.