I'll see if I can do something about it, but I *really* would like to avoid increasing the size of a `jsdisp_t` at all, honestly, because this is just for `WeakMaps` out of all objects, and seems way overkill for such a small case (but it would impact literally every object). And even if we do need the GC for it (which I think we'll need to anyway, due to cyclic refs in the WeakMap's value holding ref to the key, etc), it's not as big a deal since it's only the jsdisp_t struct itself that had weak refs that will linger as a "zombie", not even its refs to other objects.