As far as perf goes, a callee raising an exception is never the answer. The perf arguments are a sham imo. A callee cannot know how many times it is going to

As far as perf goes, a callee raising an exception is never the answer. The perf arguments are a sham imo. A callee cannot know how many times it is going to be called, only a caller, or a caller's caller, etc, can know that.