anchor.diff:      "mirror://gnu/bison/bison-${version}.tar.xz"
     ];
   
  -  version = "3.0.5";
  +  version = "3.1";
   in
   stdenv.mkDerivation rec {
     name = "bison-${version}";
  
positive.code:   passthru = {
      srcVerification = fetchurl rec {
        failEarly = true;
        urls = tarballUrls "3.0.5";
        pgpsigUrls = map (n: "${n}.sig") urls;
        pgpKeyFingerprint = "7DF8 4374 B1EE 1F97 64BB  E25D 0DDC AA32 78D5 264E";
        inherit (src) outputHashAlgo;
        outputHash = "075cef2e814642e30e10e8155e93022e4a91ca38a65aa1d5467d4e969f97f338";
      };
    };
  
  
negative.code:   src = fetchurl {
      urls = tarballUrls version;
      hashOutput = false;
      sha256 = "7c2464ad6cb7b513b2c350a092d919327e1f63d12ff024836acbb504475da5c6";
    };
  
    nativeBuildInputs = [
  