anchor.diff:        (mkIf (!config.services.activate-system.enable && cfg.distributedBuilds) "services.activate-system is not enabled, a reboot could cause distributed builds to stop working.")
         (mkIf (!cfg.distributedBuilds && cfg.buildMachines != []) "nix.distributedBuilds is not enabled, build machines won't be configured.")
       ];
  -
  -    nix.settings.substituters = mkAfter [ https://cache.nixos.org/ ];
  -    nix.settings.trusted-public-keys = mkAfter [ "cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=" ];
   
       nix.nixPath = mkMerge [
         (mkIf (config.system.stateVersion < 2) (mkDefault
  
positive.code: 
      environment.etc."nix/nix.conf".source = nixConf;
  
      environment.etc."nix/nix.conf".knownSha256Hashes = [
        "7c2d80499b39256b03ee9abd3d6258343718306aca8d472c26ac32c9b0949093"  # nix installer
        "19299897fa312d9d32b3c968c2872dd143085aa727140cec51f57c59083e93b9"
  
negative.code:     allowedUsers = "allowed-users";
      # systemFeatures = "system-features";
    };
  
    semanticConfType = with types;
      let
        confAtom = nullOr
          (oneOf [
            bool
            int
            float
            str
            path
            package
          ]) // {
          description = "Nix config atom (null, bool, int, float, str, path or package)";
        };
      in
      attrsOf (either confAtom (listOf confAtom));
  
  in
  
  