I’m guilting of writing a “can’t happen” branch (as I’m sure many of us are).

I stripped it out before production after verifying it couldn’t actually happen but it was something like an artefact of my thinking process while writing the code.

It feels like a kind of assertion of underlying assumptions, and I know enough to know I’m fallible.

I’m always careful to make the error message something reasonable if it ever did actually come up in a tech demo or something though. Anything else is tempting the Fates.