anchor.diff:    });
   
     nixUnstable = lib.lowPrio (callPackage common rec {
  -    name = "nix-2.3${suffix}";
  -    suffix = "pre6895_84de821";
  -    src = fetchFromGitHub {
  -      owner = "NixOS";
  -      repo = "nix";
  -      rev = "84de8210040580ce7189332b43038d52c56a9689";
  -      sha256 = "062pdly0m2hk8ly8li5psvpbj1mi7m1a15k8wyzf79q7294l5li3";
  -    };
  -    fromGit = true;
  +    name = "nix-2.4${suffix}";
  +    suffix = "pre7250_94c93437";
  +    src = fetchurl {
  +      url = "https://hydra.nixos.org/build/112193977/download/3/nix-2.4${suffix}.tar.xz";
  +      sha256 = "f9baf241c9449c1e3e5c9610adbcd2ce9e5fbcab16aff3ba3030d2fad7b34d7b";
  +    };
   
       inherit storeDir stateDir confDir boehmgc;
     });
   
     nixFlakes = lib.lowPrio (callPackage common rec {
       name = "nix-2.4${suffix}";
  -    suffix = "pre20191022_9cac895";
  -    src = fetchFromGitHub {
  -      owner = "NixOS";
  -      repo = "nix";
  -      rev = "9cac895406724e0304dff140379783c4d786e855";
  -      hash = "sha256-Y1cdnCNoJmjqyC/a+Nt2N+5L3Ttg7K7zOD7gmtg1QzA=";
  -    };
  -    fromGit = true;
  +    suffix = "pre20200207_d2032ed";
  +    src = fetchurl {
  +      url = "https://hydra.nixos.org/build/111815420/download/3/nix-2.4${suffix}.tar.xz";
  +      sha256 = "e72a20efeee4ccc704cca3a06de9185fb8742bc7ef1a62af5896ec0f379b9ceb";
  +    };
   
       inherit storeDir stateDir confDir boehmgc;
     });
  
positive.code:   , withLibseccomp ? lib.any (lib.meta.platformMatch stdenv.hostPlatform) libseccomp.meta.platforms, libseccomp
    , withAWS ? stdenv.isLinux || stdenv.isDarwin, aws-sdk-cpp
  
    , name, suffix ? "", src, includesPerl ? false, fromGit ? false
  
    }:
    let
  
negative.code: { lib, fetchurl, callPackage
  , storeDir ? "/nix/store"
  , stateDir ? "/nix/var"
  , confDir ? "/etc"
  