anchor.diff:      ghc bootPkgs.alex bootPkgs.happy bootPkgs.hscolour
     ] ++ lib.optionals enableDocs [
       sphinx
  -  ] ++ lib.optionals stdenv.isDarwin [
  -    # TODO(@sternenseemann): use XATTR env var once we have
  -    # https://gitlab.haskell.org/ghc/ghc/-/merge_requests/6447
  -    xattr
     ];
   
     # For building runtime libs
  
positive.code: , # Whether to build terminfo.
    enableTerminfo ? !stdenv.targetPlatform.isWindows
  
  , version ? "9.3.20210806"
  , # What flavour to build. An empty string indicates no
    # specific flavour and falls back to ghc default values.
    ghcFlavour ? lib.optionalString (stdenv.targetPlatform != stdenv.hostPlatform)
  
negative.code: 
    src = fetchgit {
      url = "https://gitlab.haskell.org/ghc/ghc.git/";
      rev = "64923cf295ea914db458547432237a5ed1eff571";
      sha256 = "1s9sm4gf4r71lk0s7h9v217rxfwjf435q1jji90hlxz23wvmhr6d";
    };
  
    enableParallelBuilding = true;
  