Hi, this is my ~/.nixpkgs/config.nix.
All the packages listed there work, in the sense that they are recognised by emacs+haskellMode, ghci and ghc during normal operations.

The package sbv, however, does not: it isn't recognized by emacs, and when I try to import it in ghci or compile a file importing it, I get an error along the lines of:

Could not find module ‘Data.SBV’
Perhaps you meant Data.Set (from containers-0.5.5.1)
Use -v to see a list of the files searched for.

Do you have the same problem?

Edit: I'm on nixos-unstable