anchor.diff:    meta = with stdenv.lib; {
       description = "An OpenType text shaping engine";
       homepage = http://www.freedesktop.org/wiki/Software/HarfBuzz;
  +    downloadPage = "https://www.freedesktop.org/software/harfbuzz/release/";
       maintainers = [ maintainers.eelco ];
       platforms = with platforms; linux ++ darwin;
  +    inherit version;
  +    updateWalker = true;
     };
   }
  
positive.code: }:
  
  let
    version = "1.2.7";
    inherit (stdenv.lib) optional optionals optionalString;
  in
  
  
negative.code: 
    src = fetchurl {
      url = "http://www.freedesktop.org/software/harfbuzz/release/harfbuzz-${version}.tar.bz2";
      sha256 = "18c9rzg4ilmhbx8hpdhcjffkzq5smcbc2lr23g6fdm8rs5nj0hm2";
    };
  
    outputs = [ "out" "dev" ];
  