anchor.diff:          If unset, it defaults to the platform type of your host system.
           Specifying this option is useful when doing distributed
           multi-platform deployment, or when building virtual machines.
  +
  +        Ignored when <code>nixpkgs.pkgs</code> is set.
         '';
       };
     };
   
     config = {
       _module.args = {
  -      pkgs = _pkgs;
  -      pkgs_i686 = _pkgs.pkgsi686Linux;
  +      pkgs = cfg.pkgs;
  +      pkgs_i686 = cfg.pkgs.pkgsi686Linux;
       };
     };
   }
  
positive.code: with lib;
  
  let
    isConfig = x:
      builtins.isAttrs x || builtins.isFunction x;
  
  
negative.code:     merge = lib.mergeOneOption;
    };
  
    pkgsType = mkOptionType {
      name = "nixpkgs";
      description = "An evaluation of Nixpkgs; the top level attribute set of packages";
      check = builtins.isAttrs;
    };
  
  in
  
  {
    options.nixpkgs = {
  
      pkgs = mkOption {
        defaultText = literalExample
          ''import "''${nixos}/.." {
              inherit (config.nixpkgs) config overlays system;
            }
          '';
        default = import ../../.. { inherit (cfg) config overlays system; };
        type = pkgsType;
        example = literalExample ''import <nixpkgs> {}'';
        description = ''
          This is the evaluation of Nixpkgs that will be provided to
          all NixOS modules. Defining this option has the effect of
          ignoring the other options that would otherwise be used to
          evaluate Nixpkgs, because those are arguments to the default
          value. The default value imports the Nixpkgs source files
          relative to the location of this NixOS module, because
          NixOS and Nixpkgs are distributed together for consistency,
          so the <code>nixos</code> in the default value is in fact a
          relative path. The <code>config</code>, <code>overlays</code>
          and <code>system</code> come from this option's siblings.
  
          This option can be used by applications like NixOps to increase
          the performance of evaluation, or to create packages that depend
          on a container that should be built with the exact same evaluation
          of Nixpkgs, for example. Applications like this should set
          their default value using <code>lib.mkDefault</code>, so
          user-provided configuration can override it without using
          <code>lib</code>.
  
          Note that using a distinct version of Nixpkgs with NixOS may
          be an unexpected source of problems. Use this option with care.
        '';
      };
  
      config = mkOption {
        default = {};
        example = literalExample
  