anchor.diff:          outputHash
           outputHashAlgo
           urls;
  -      sha256Url = "https://download.gnome.org/sources/clutter-gst/"
  -        + "${channel}/${name}.sha256sum";
  +      fullOpts = {
  +        sha256Url = map (n: (lib.replaceStrings ["tar.xz"] ["sha256sum"] n)) src.urls;
  +      };
         failEarly = true;
       };
     };
  
positive.code:   src = fetchurl {
      url = "mirror://gnome/sources/clutter-gst/${channel}/${name}.tar.xz";
      hashOutput = false;
      sha256 = "d8618a6d9accec0f2a8574c5e1220051f8505fb82b20336c26bdbd482aa6cb3a";
    };
  
    buildInputs = [
  
negative.code:     optionals;
  
    channel = "3.0";
    version = "${channel}.27";
  in
  stdenv.mkDerivation rec {
    name = "clutter-gst-${version}";
  