anchor.diff:    passthru = {
       srcVerification = fetchurl {
         failEarly = true;
  -      sha256Url = "https://download.gnome.org/sources/libcroco/${versionMajor}/"
  -        + "${name}.sha256sum";
         inherit (src) urls outputHash outputHashAlgo;
  +      fullOpts = {
  +        sha256Url = "https://download.gnome.org/sources/libcroco/${versionMajor}/"
  +          + "${name}.sha256sum";
  +      };
       };
     };
   
  
positive.code: 
  let
    versionMajor = "0.6";
    versionMinor = "12";
    version = "${versionMajor}.${versionMinor}";
  in
  stdenv.mkDerivation rec {
  
negative.code:   src = fetchurl {
      url = "mirror://gnome/sources/libcroco/${versionMajor}/${name}.tar.xz";
      hashOutput = false;
      sha256 = "767ec234ae7aa684695b3a735548224888132e063f92db585759b422570621d4";
    };
  
    buildInputs = [
  