anchor.diff:        inherit ihaskellBuildEnvFunc;
       };
     };
  -
  -  ihaskellBuildEnv = ihaskellBuildEnvFunc {
  -    inherit ihaskellEnv jupyterlab ihaskellDataDir systemPackages;
  -  };
  -
  -in ihaskellBuildEnv
  +in ihaskellBuildEnvFunc {
  +  inherit ihaskellEnv jupyterlab systemPackages;
  +  ihaskellDataDir = let
  +    ihaskellGhcLib =  ihaskellGhcLibFunc ihaskellExe ihaskellEnv;
  +    ihaskellKernelFile = ihaskellKernelFileFunc ihaskellGhcLib rtsopts;
  +    ihaskellKernelSpec = ihaskellKernelSpecFunc ihaskellKernelFile;
  +  in ihaskellDataDirFunc ihaskellKernelSpec ihaskellLabextension;
  +}
  
positive.code:         fi
        done
      '';
  
      passthru = {
        inherit haskellPackages;
        inherit ihaskellExe;
  
negative.code:   ihaskellExe = nixpkgs.haskell.lib.justStaticExecutables haskellPackages.ihaskell;
    ihaskellEnv = haskellPackages.ghcWithPackages packages;
    jupyterlab = nixpkgs.python3.withPackages (ps: [ ps.jupyterlab ] ++ pythonPackages ps);
    ihaskellGhcLibFunc = exe: env: nixpkgs.writeShellScriptBin "ihaskell" ''
      ${exe}/bin/ihaskell -l $(${env}/bin/ghc --print-libdir) "$@"
    '';
    ihaskellKernelFileFunc = ihaskellGhcLib: rtsopts: {
      display_name = "Haskell";
      argv = [
  