I usually annotate should-never-happen asserts by the most plausible explanation how it _could_ happen, for the sake of some poor guy unlucky enough for having

I usually annotate should-never-happen asserts by the most plausible explanation how it _could_ happen, for the sake of some poor guy unlucky enough for having to debug my code. E.g. "Should not happen — probably a bug in Apache Commons Math?" Or "Shouldn't really happen, barring compiler bugs or cosmic rays" As they told us, there is no such thing as probability of zero.