anchor.diff:  in
   stdenv.mkDerivation rec {
     name = "nextpnr-${version}";
  -  version = "2019.02.20";
  +  version = "2019.04.02";
   
     src = fetchFromGitHub {
       owner  = "yosyshq";
       repo   = "nextpnr";
  -    rev    = "e8d3aaaf34895a073e4023192d97fc936d090990";
  -    sha256 = "0ijqpjnn7x16crd6cmd4nmgay320flizmjb7bbvg9hv464z3p4x7";
  +    rev    = "6adf37e3c1d4301e087d89c9e9c37563fe8d78df";
  +    sha256 = "0qqb2yd2s39hahh5qigvllgyzj7rp3r1k9jp2n9z2jrfpiaz68c6";
     };
   
     nativeBuildInputs = [ cmake makeWrapper ];
     buildInputs
  -     = [ boostPython python3 ]
  +     = [ boostPython python3 eigen ]
       ++ (stdenv.lib.optional enableGui qtbase);
   
     enableParallelBuilding = true;
  
positive.code:   postInstall = stdenv.lib.optionalString enableGui ''
      for x in generic ice40 ecp5; do
        wrapProgram $out/bin/nextpnr-$x \
          --prefix QT_PLUGIN_PATH : ${qtbase}/lib/qt-${qtbase.qtCompatVersion}/plugins
      done
    '';
  
  
negative.code: { stdenv, fetchFromGitHub, cmake, makeWrapper
  , boost, python3, eigen
  , icestorm, trellis
  
  # TODO(thoughtpolice) Currently the GUI build seems broken at runtime on my
  