code: function accumulateDirectionalDispatches(inst, phase, event) {
    {
      warning$29(inst, 'Dispatching inst must not be null');
    }
    var listener = listenerAtPhase(inst, event, phase);
    if (listener) {
      event._dispatchListeners = accumulateInto_1(event._dispatchListeners, listener);
      event._dispatchInstances = accumulateInto_1(event._dispatchInstances, inst);
    }
  }
docs: Tags a `SyntheticEvent` with dispatched listeners. Creating this function
  here, allows us to not have to bind or create functions for each event.
  Mutating the event's members allows us to not have to create a wrapping
  "dispatch" object that pairs the event with the listener.