Gtk toArray List funkiness

[Joseph via Digitalmars-d-learn]

https://github.com/gtkd-developers/GtkD/blob/master/demos/gtkD/TestWindow/TestWindow.d

has the code

foreach ( int i, string selection ; fs.getSelections())
{
   writeln("File(s) selected [%d] %s",i,selection);
}

which is invalid for the demo, but

foreach ( int i, string selection ; 
fd.getFilenames().toArray!(string,?))
{
   writeln("File(s) selected [%d] %s",i,selection);
}

results in some funky code. Gives errors in ObjectG about uint 
when setting ? to string, string* or void* or even uint:

GtkD\generated\gtkd\gobject\ObjectG.d(172): Error: incompatible 
types for ((obj) is (null)): 'uint' and 'typeof(null)'
GtkD\generated\gtkd\glib\ListSG.d(98): Error: template instance 
gobject.ObjectG.ObjectG.getDObject!(string, string, uint) error 
instantiating
test.d(91):        instantiated from here: toArray!(string, uint)
test.d(93): Error: invalid foreach aggregate `fd.getFilenames()`, 
define opApply(), range primitives, or use .tupleof

without specifying ? it assumes it's a tuple, which seems wrong?



	public T[] toArray(T, TC = typeof(T.tupleof[0]))()
	{
		T[] arr = new T[length()];
		ListSG list = this;
		size_t count;

		while(list !is null && count < arr.length)
		{
			arr[count] = ObjectG.getDObject!(T)(cast(TC)list.data);
			list = list.next();
			count++;
		}

		return arr;
	}


										foreach ( int i, Value selection ; 
fd.getFilenames().toArray!(Value)())
{
   writeln("File(s) selected [%d] %s",i,selection.getString);
}

crashes ;/

I'm not sure what types are what and it changes depending on the 
input. I think Value is the wrong type to use but string doesn't 
work so...