BreakPoint
D'oh!
I just tracked down a subtle bug in my code -- this syntax was the culprit:
That's all!
Just sharing a silly bug that cost about a half-hour, intentionally starting a new thread to protest the megathreads that now dominate Breakpoint 
@Alex.T wrote:
Do you think it'd be worth as posting as an idea?
It's a cool idea, but one problem with it is that it can only refer to the indices of the primitive itself (i.e. if someone wires a value into one of the inputs and that value is not a constant, then there's no way of knowing what the index in the array would be). I would suggest a modification - if a constant is wired into the primitive (or no value at all), then the primitive shows the indices until the next value wired into an input. Otherwise, it shows the same square which was there until now. I would show that as a demo image in the idea. I would also add an expection where if the index value is large and won't fit into the primitive, the output would show a square instead.
