haskellPackages.callPackage: preserve functionArgs (#443442)

      # is that nix has no way to "passthrough" args while preserving the reflection

      # info that callPackage uses to determine the arguments).

      drv = if lib.isFunction fn then fn else import fn;

      auto = builtins.intersectAttrs (lib.functionArgs drv) scope;

      drvFunctionArgs = lib.functionArgs drv;

      auto = builtins.intersectAttrs drvFunctionArgs scope;

      # Converts a returned function to a functor attribute set if necessary

      ensureAttrs = v: if builtins.isFunction v then { __functor = _: v; } else v;

      # this wraps the `drv` function to add `scope` and `overrideScope` to the result.

      drvScope =

        allArgs:

      # it's a functor, so that we can pass through `functionArgs`

      drvScope = {

        __functor =

          _: allArgs:

          ensureAttrs (drv allArgs)

          // {

            inherit scope;

              # nothing.

              callPackageWithScope newScope drv manualArgs;

          };

        # `drvScope` accepts the same arguments as `drv`

        __functionArgs = drvFunctionArgs;

      };

    in

    lib.makeOverridable drvScope (auto // manualArgs);