removing a template element should cause its instances to be removed

[rafaelw]

This is consistent with the "strong connection" view of templates and instances

[ajklein]

If this is done asynchronously as we discussed, it seems pretty tricky. How will the template know, when it's actually going about tearing down instances, where the first instance starts? That's just the first problem. I think the synchronous behavior of fixing-up terminators can also bite us, since a naive implementation could let terminators move before the old start of the template instance.

Both of the above problems seem like their solution will be another hidden bit like the instance terminator, but designating the first node of an instance. Along with some way for the template to find that node, and to keep it updated if that node is removed before the template starts doing its work.

It's not obvious to me, though, that this is all worthwhile. Are abandoned instances causing problems for us?

[ajklein]

Strawman: when abandoning the instance, make a note (Vector<RefPtr<Node> >) of which nodes are currently in the instance(s), and their parent. If, later, those nodes are still on that parent, remove them.