These string[][] problems are making any "aas" reply not usable in Vala:

Async situation:

error: internal error: duplicating string[] instances not yet supported
	private void on_get_stats (string [][] items, GLib.Error e) {
				   ^^^^^^^^^^^^^^^^^

private void on_get_stats (string [][] items, GLib.Error e) {
	foreach (string [] pair in items) {
		print ("k:" + pair[0] + " v:" + pair[1] + "\n");
	}
}

Facade.Instance().tracker.GetStats (on_get_stats);

Non-async situation:

error: internal error: duplicating string[] instances not yet supported
		string[][] tags;


dynamic DBus.Object tracker = ...

private void get_numbers () {
	string[][] tags;

	tracker.GetStats ();
	foreach (string [] pair in tags) {
		print ("k:" + pair[0] + " v:" + pair[1] + "\n");
	}
}


Weak strings, non-async:

Segmentation fault (core dumped)

dynamic DBus.Object tracker = ...

private void get_numbers () {
	string[][] tags;

	tracker.GetStats ();
	foreach (weak string [] pair in tags) {
		print ("k:" + pair[0] + " v:" + pair[1] + "\n");
	}
}