anchor.diff:    src = fetchurl {
       url = "https://github.com/mongodb/libbson/releases/download"
         + "/${version}/${name}.tar.gz";
  -    sha256 = "0d1de4aa2ea4b223414c1b1aa803fc50d1ab658b327aead857fb4915136d4e34";
  +    sha256 = "244e786c746fe6326433b1a6fcaadbdedc0da3d11c7b3168f0afa468f310e5f1";
     };
   
     nativeBuildInputs = [
  
positive.code:     ln -sv . "$incdir"
    '';
  
    meta = with stdenv.lib; {
      maintainers = with maintainers; [
        wkennington
      ];
  
negative.code: { stdenv
  , fetchurl
  , lib
  , perl
  }:
  
  let
    version = "1.9.3";
  in
  stdenv.mkDerivation rec {
    name = "libbson-${version}";
  