Override haskellPackages

config.nix

{ pkgs }:

{
  packageOverrides = self: rec {
    haskellPackages_ghcHEAD = self.haskell.packages {
      ghcPath = /home/shana/programming/ghc;
      ghcBinary = self.haskellPackages.ghcPlain;
      prefFun = self.haskell.ghcHEADPrefs;
      extraArgs = {
        happy = self.haskellPackages.happy_1_19_2;
        alex = self.haskellPackages.alex_3_1_3;
      };
    };
  };
}