haskell-override-package-version

  nixpkgs.config.packageOverrides = pkgs:
  {
    haskellPackages = pkgs.haskellPackages.override {
      overrides = self: super:
      {
        apply-refact = pkgs.haskell.lib.overrideCabal super.apply-refact (drv: {version = ".."; sha256 = ".."; });
      };
    };
  };