alt Hacker NewsA comment "this CANNOT happen" has no value on itself. Unless you've formally verified the code (including its dependencies) and have the proof linked, such comments may as well be wishes and prayers.
Yes, sometimes, the compiler or the hardware have bugs that violate the premises you're operating on, but that's rare. But most non pure algorithms (side effects and external systems) have documented failure cases.
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False it has value. It’s actually even better to log it or throw an exception. print(“this cannot happen.”)
If you see it you immediately know the class of error is purely a logic error the programmer made a programming mistake. Logging it makes it explicit your program has a logic bug.
What if you didn’t log it? Then at runtime you will have to deduce the error from symptoms. The log tells you explicitly what the error is.
Worse: You may created the proof. You may have linked to the proof. But if anyone has touched any of the code involved since then, it still has no value unless someone has re-done the proof and linked that. (Worse, it has negative value, because it can mislead.)
> A comment "this CANNOT happen" has no value on itself.
I think it does have some value: it makes clear an assumption the programmer made. I always appreciate it when I encounter comments that clarify assumptions made.