anchor.diff:  }:
   
   let
  -  version = "2.9.8";
  +  version = "2.9.9";
   
     tarballUrls = version: [
       "http://xmlsoft.org/sources/libxml2-${version}.tar.gz"
  
positive.code: 
    src = fetchurl {
      urls = tarballUrls version;
      multihash = "QmNzhnPYCnLukCSrycQNEkxJsghY9KP45cKeLqiKxxf6Ca";
      hashOutput = false;
      sha256 = "0b74e51595654f958148759cfef0993114ddccccbb6f31aee018f3558e8e2732";
    };
  
    buildInputs = [
  
negative.code:   passthru = {
      srcVerification = fetchurl rec {
        failEarly = true;
        urls = tarballUrls "2.9.9";
        inherit (src) outputHashAlgo;
        outputHash = "94fb70890143e3c6549f265cee93ec064c80a84c42ad0f23e85ee1fd6540a871";
        fullOpts = {
          pgpsigUrls = map (n: "${n}.asc") urls;
          pgpKeyFingerprint = "C744 15BA 7C9C 7F78 F02E  1DC3 4606 B8A5 DE95 BC1F";
        };
      };
    };
  
  