code: function realDone(_base) {
              _this10._base = _base;
              return _this10.onSet.pub([old, _this10._base]);
            }
docs: TODO we are immediately disconnecting; something that disconnects upon completion may have better semantics for asynchronous operations:  - enabling lagBind to defer evaluation so long as its current dependencies keep changing - allowing nested binds to continue reacting during asynchronous operation  But the implementation is more complex as it requires being able to create and discard tentative recordings.  It's also unclear whether such a lagBind is more desirable (in the face of changing dependencies) and whether on-completion is what's most generalizable.