anchor.diff:  
   stdenv.mkDerivation rec {
     pname = "haproxy";
  -  version = "1.9.8";
  +  version = "2.0.8";
   
     src = fetchurl {
       url = "https://www.haproxy.org/download/${stdenv.lib.versions.majorMinor version}/src/${pname}-${version}.tar.gz";
  -    sha256 = "1via9k84ycrdr8qh4qchcbqgpv0gynm3ra23nwsvqwfqvc0376id";
  +    sha256 = "02i87hr1dfhrk6nvvcig4m9bpww7hyl6qcxcl20rfvxd2n2iwzn3";
     };
   
     buildInputs = [ openssl zlib ]
  -    ++ stdenv.lib.optional useLua lua5_3
  -    ++ stdenv.lib.optional usePcre pcre;
  +    ++ lib.optional useLua lua5_3
  +    ++ lib.optional usePcre pcre
  +    ++ lib.optional stdenv.isLinux systemd;
   
     # TODO: make it work on bsd as well
     makeFlags = [
       "PREFIX=\${out}"
       ("TARGET=" + (if stdenv.isSunOS  then "solaris"
  -             else if stdenv.isLinux  then "linux2628"
  +             else if stdenv.isLinux  then "linux-glibc"
                else if stdenv.isDarwin then "osx"
                else "generic"))
     ];
  +
     buildFlags = [
       "USE_OPENSSL=yes"
       "USE_ZLIB=yes"
  -  ] ++ stdenv.lib.optionals usePcre [
  +  ] ++ lib.optionals usePcre [
       "USE_PCRE=yes"
       "USE_PCRE_JIT=yes"
  -  ] ++ stdenv.lib.optionals useLua [
  +  ] ++ lib.optionals useLua [
       "USE_LUA=yes"
       "LUA_LIB=${lua5_3}/lib"
       "LUA_INC=${lua5_3}/include"
  -  ] ++ stdenv.lib.optional stdenv.isDarwin "CC=cc"
  -    ++ stdenv.lib.optional stdenv.isLinux "USE_GETADDRINFO=1";
  +  ] ++ lib.optionals stdenv.isLinux [
  +    "USE_SYSTEMD=yes"
  +    "USE_GETADDRINFO=1"
  +  ] ++ lib.optionals withPrometheusExporter [
  +    "EXTRA_OBJS=contrib/prometheus-exporter/service-prometheus.o"
  +  ] ++ lib.optional stdenv.isDarwin "CC=cc";
   
  -  meta = {
  +  enableParallelBuilding = true;
  +
  +  meta = with lib; {
       description = "Reliable, high performance TCP/HTTP load balancer";
       longDescription = ''
         HAProxy is a free, very fast and reliable solution offering high
  
positive.code:       tens of thousands of connections is clearly realistic with todays
        hardware.
      '';
      homepage = http://haproxy.1wt.eu;
      maintainers = with stdenv.lib.maintainers; [ fuzzy-id ];
      platforms = with stdenv.lib.platforms; linux ++ darwin;
      license = stdenv.lib.licenses.gpl2;
    };
  }
  
negative.code: { useLua ? !stdenv.isDarwin
  , usePcre ? true
  , withPrometheusExporter ? true
  , stdenv, lib, fetchurl
  , openssl, zlib
  , lua5_3 ? null, pcre ? null, systemd ? null
  }:
  
  assert useLua -> lua5_3 != null;
  