anchor.diff:  { stdenv, fetchFromGitHub, cmake
   , boost, python3, eigen
   , icestorm, trellis
  +, llvmPackages
   
   , enableGui ? true
   , wrapQtAppsHook
  
positive.code: in
  with stdenv; mkDerivation rec {
    pname = "nextpnr";
    version = "2019.08.21";
  
    src = fetchFromGitHub {
      owner  = "yosyshq";
      repo   = "nextpnr";
      rev    = "c192ba261d77ad7f0a744fb90b01e4a5b63938c4";
      sha256 = "0g2ar1z89b31qw5vgqj2rrcv9rzncs94184dgcsrz19p866654mf";
    };
  
    nativeBuildInputs
  
negative.code:     ++ (lib.optional enableGui wrapQtAppsHook);
    buildInputs
       = [ boostPython python3 eigen ]
      ++ (lib.optional enableGui qtbase)
      ++ (lib.optional stdenv.cc.isClang llvmPackages.openmp);
  
    enableParallelBuilding = true;
    cmakeFlags =
  