However, constexpr I still do not agree. Following your logic, we should add constexpr to every single function everywhere - these are as likely to have constant parameters as get_i (which has like 0.00000001% chance that first parameter will be const in real code).

enum e {
  e01 = 1,
  e02 = 100,
  e03 = e01 + e02
};

enum e {
  e01 = min(something, something_else),
  e02 = max(something, something_else)
};