anchor.diff:    inherit version;
     inherit meta;
   
  +  __impureHostDeps = [ "/usr/lib/libedit.3.dylib" ];
  +
     src = if isRelease then
         fetchzip {
           url = "http://static.rust-lang.org/dist/rustc-${version}-src.tar.gz";
  
positive.code:     installPhase = ''
        mkdir -p "$out"
        cp -r bin "$out/bin"
      '' + (if stdenv.isLinux then ''
        patchelf --interpreter "${stdenv.glibc}/lib/${stdenv.cc.dynamicLinker}" \
                 --set-rpath "${stdenv.cc.cc}/lib/:${stdenv.cc.cc}/lib64/" \
                 "$out/bin/rustc"
      '' else "");
    };
  
    configureFlags = configureFlags
                  ++ [ "--enable-local-rust" "--local-rust-root=$snapshot" ]
                  ++ stdenv.lib.optional (stdenv.cc ? clang) "--enable-clang";
  
    inherit patches;
  
  
negative.code:       --replace /bin/echo "${coreutils}/bin/echo"
    '';
  
    buildInputs = [ which file perl curl python27 makeWrapper git ]
      ++ stdenv.lib.optionals (!stdenv.isDarwin) [ procps valgrind ];
  
    enableParallelBuilding = true;
  
  