[Vala] Async call GLib.IOStream.splice_async failed!

[Heiher <root heiher info>]

Hello,

vala codes:
public static int main (string args[]) {
        GLib.IOStream? is0 = null;
        GLib.IOStream? is1 = null;

        is0.splice_async.begin (is1, GLib.IOStreamSpliceFlags.NONE,
                                GLib.Priority.DEFAULT, null, (obj, res) => {
                try {
                        is0.splice_async.end (res);
                } catch (GLib.Error e) {
                }
        });

        return 0;
}

compile errors:
$ valac -X -w -o test test.vala --pkg gio-2.0
/home/heiher/work/test.vala.c: In function ‘__lambda2_’:
/home/heiher/work/test.vala.c:51:3: error: too many arguments to
function ‘g_io_stream_splice_finish’
   g_io_stream_splice_finish (_data1_->is0, _tmp0_, &_inner_error_);
   ^
In file included from /usr/include/glib-2.0/gio/gfileiostream.h:30:0,
                 from /usr/include/glib-2.0/gio/gio.h:71,
                 from /home/heiher/work/test.vala.c:9:
/usr/include/glib-2.0/gio/giostream.h:104:16: note: declared here
 gboolean       g_io_stream_splice_finish     (GAsyncResult         *result,
                ^
error: cc exited with status 256
Compilation failed: 1 error(s), 0 warning(s)

Thx!