Please make missing @tool annotation errors easier to find

[blackears]

I've been playing around with making objects and plugins for Godot and I'm finding that when I accidentally leave out a @tool tag, it makes for some hard to track down errors. I don't know how easy it would be, but if something that runs in the editor tries to instantiate something that ought to be a @tool and the annotation is missing, could a warning be printed along the lines of "Warning: Tried to instantiate a non-tool object"?