anchor.diff:  let
   
     inherit (stdenv.lib) optional optionals optionalString versionOlder
  -                       concatStringsSep enableFeature optionalAttrs;
  +                       concatStringsSep enableFeature optionalAttrs toUpper;
   
     isGhcjs = ghc.isGhcjs or false;
   
  
positive.code:       LANG = "en_US.UTF-8";
        LOCALE_ARCHIVE = optionalString stdenv.isLinux "${glibcLocales}/lib/locale/locale-archive";
        shellHook = ''
          export NIX_GHC="${ghcEnv}/bin/${ghcCommand}"
          export NIX_GHCPKG="${ghcEnv}/bin/${ghcCommand}-pkg"
          export NIX_GHC_DOCDIR="${ghcEnv}/share/doc/ghc/html"
          export NIX_GHC_LIBDIR="${ghcEnv}/lib/${ghcEnv.name}"
        '';
      };
  
  
negative.code: 
    setupCommand = if isGhcjs then "${ghc.nodejs}/bin/node ./Setup.jsexe/all.js" else "./Setup";
    ghcCommand = if isGhcjs then "ghcjs" else "ghc";
    ghcCommandCaps = toUpper ghcCommand;
  
  in
  stdenv.mkDerivation ({
  