@ReinstateMonica3167040 Well, this states the rules but not the reason: The compiler "knows" perfectly well which branch will be executed,
constexpr or not, and could hence compile it perfectly identically with or without it. I can think of only two reasons constexpr was introduced: 1. Errors in the branch not taken are in some cases intentional to prevent compilation (e.g. for certain template type arguments). Changing the language and demanding that the not-taken branch was not compiled would break backwards compatibility. 2. Flag cases that are actually not compile-time decidable.