[_b]

I think the dilemma for C++ exceptions is that if the programmer actually thinks something should never happen, it is almost always better to just crash. But if the programmer thinks it might happen sometimes, then it is risky to predict it is will be super rare, as often this code will be called in different contexts in the future, so it is safer to use normal returns and flow control. As a result, throwing an exception is basically never the best thing to do.