anchor.diff:    src = fetchurl {
       url = "mirror://gnome/sources/pango/${channel}/${name}.tar.xz";
       hashOutput = false;
  -    sha256 = "9924d88a3dcedff753f0763814a1605307c5c9c931413b8b47ea7267d1b19446";
  +    sha256 = "b1e416b4d40416ef6c8224cf146492b86848703264ba88f792290992cf3ca1e2";
     };
   
     nativeBuildInputs = [
  
positive.code:     optionalString;
  
    channel = "1.42";
    version = "${channel}.0";
  in
  stdenv.mkDerivation rec {
    name = "pango-${version}";
  
negative.code:     "-Denable_docs=false"  # gtk-doc
      "-Dgir=true"
    ];
  
    # preCheck = /* Fontconfig fails to load default config in test */
    #     optionalString doCheck ''
  