anchor.diff:    passthru = {
       srcVerification = fetchurl rec {
         failEarly = true;
  -      urls = tarballUrls "4.10";
  +      urls = tarballUrls "4.12";
         pgpsigUrls = map (n: "${n}.sig") urls;
         pgpKeyFingerprint = "1F42 4189 05D8 206A A754  CCDC 29EE 58B9 9686 5171";
  -      outputHash = "681a4d9a0d259f2125713f2e5766c5809f151b3a1392fd91390f780b4b8f5a02";
  +      outputHash = "6753da2e621257f33f5b051cc114d417e5206a0818fe0b1ecfd6153f70934753";
         inherit (src) outputHashAlgo;
       };
     };
  
positive.code:   src = fetchurl {
      urls = tarballUrls version;
      hashOutput = false;
      sha256 = "681a4d9a0d259f2125713f2e5766c5809f151b3a1392fd91390f780b4b8f5a02";
    };
  
    nativeBuildInputs = [
  
negative.code:     "mirror://gnu/libtasn1/libtasn1-${version}.tar.gz"
    ];
  
    version = "4.12";
  in
  stdenv.mkDerivation rec {
    name = "libtasn1-${version}";
  