I'm thinking of other repairers, like a probabalistic repairer or a load-dependent repairer, that might bulk-discard requests, in which case it's handy to call "RepairDiscarded(len(requests))".

(Thinking about it: We could even make the NopRepairer call RepairCall(), RepairRequestCount() and then RepairDiscarded() on everything to get a sense of the number of repairs that would have been performed if we had switched on repairs.)