anchor.diff:    pname = "icestorm";
     version = "2019.09.13";
   
  -  pythonPkg = if usePyPy then pypy3 else python3;
  -  pythonInterp = pythonPkg.interpreter;
  +  passthru = rec {
  +    pythonPkg = if usePyPy then pypy3 else python3;
  +    pythonInterp = pythonPkg.interpreter;
  +  };
   
     src = fetchFromGitHub {
       owner  = "cliffordwolf";
  
positive.code:       --replace /usr/local/share "$out/share"
  
      for x in icefuzz/Makefile icebox/Makefile icetime/Makefile; do
        substituteInPlace "$x" --replace python3 "${pythonInterp}"
      done
  
      for x in $(find . -type f -iname '*.py'); do
        substituteInPlace "$x" \
          --replace '/usr/bin/env python3' '${pythonInterp}'
      done
    '';
  
  
negative.code:   };
  
    nativeBuildInputs = [ pkgconfig ];
    buildInputs = [ passthru.pythonPkg libftdi1 ];
    makeFlags = [ "PREFIX=$(out)" ];
  
    enableParallelBuilding = true;
  