oh my bad, i got confused with the syntax when i wrote that post, just was trying to think of an example. but here's what i had that wasn't working (where _element is a struct like { x: 0, y: 0 }):
TweenFire("-duration", _tween_duration, "-target", _element, "x>", _x, "y>", _y);
this doesn't work and gives me this error:
Variable <unknown_object>.ref(100420, -2147483648) not set before reading it.but if i make the change i described in my post, it works.
at gml_Script_TGMS_Variable_Get (line 624) - target = target.ref;