anchor.diff:      '';
   
     };
  +
   }
  
positive.code: with lib;
  
  let
    cfg = config.nix;
  
    isNix20 = versionAtLeast (cfg.version or "<unknown>") "1.12pre";
  
negative.code:     allowedUsers = "allowed-users";
      # systemFeatures = "system-features";
    };
  
  in
  
  {
  