Nix configuration for cabal hacking

[Carlo Nucera]

Hi all, I will be at ZuriHack in a few days, and I'd like to start hacking on
Cabal.

I'm reading the cabal codebase description on github, and I'd like a few
suggestion on how to set up the environment, so that I won't waste time setting
up.

I use the nix package manager for all things haskell-related, so I'm wary to
just do cabal install in a sandbox, as suggested by the tutorial in the github
page.

Here it is my current ~/.nixpkgs/config.nix:
https://gist.github.com/meditans/d66371137814d0dc3707

I stripped away most of the non necessary things. As you can see from the gist,
I tried to install Cabal that as a package, but it didn't work the naive way. Is
there among you anyone that develops with nix? What's your configuration?

Thanks, see you friday!
Carlo