{ sources ? import ./sources.nix, pkgs ? import sources.nixpkgs {
   overlays = [ ];
   config = { };
 }, stdenv ? pkgs.stdenv, fetchurl ? pkgs.lib.fetchurl }:
 
 let

   nodejs = pkgs.nodejs-18_x;

   yarn = pkgs.yarn.overrideAttrs (_: { buildInputs = [ nodejs ]; });
   hp = pkgs.haskellPackages.override {
     overrides = self: super:
       let
         workaround140774 = hpkg:
           with pkgs.haskell.lib;
           overrideCabal hpkg (drv: { enableSeparateBinOutput = false; });
       in { niv = workaround140774 super.niv; };
   };
 
 in {
   shell = stdenv.mkDerivation {
     name = "shell-env";

     buildInputs = [nodejs hp.niv];

   };
   niv = hp.niv;
 }