anchor.diff:          echo -n "$darwinLabel" > $out/darwin-version
           echo -n "$system" > $out/system
         '';
  -    };
  +    }));
   
     };
   }
  
positive.code:       default = pkgs.lib.nixpkgsVersion;
      };
  
    };
  
    config = {
  
      system.build.toplevel = stdenvNoCC.mkDerivation {
        name = "darwin-system-${cfg.darwinLabel}";
        preferLocalBuild = true;
  
  
negative.code:   inherit (pkgs) stdenvNoCC;
  
    cfg = config.system;
  
    failedAssertions = map (x: x.message) (filter (x: !x.assertion) config.assertions);
  
  
    throwAssertions = res: if (failedAssertions != []) then throw "\nFailed assertions:\n${concatStringsSep "\n" (map (x: "- ${x}") failedAssertions)}" else res;
    showWarnings = res: fold (w: x: builtins.trace "[1;31mwarning: ${w}[0m" x) res config.warnings;
  
  in
  
  