- Flag(const char* name, const char* desc, T value, const std::map<std::string, std::string, std::less<>>& valid_values,
- F callback)
+ Flag(const char* name, const char* desc, xbt::type_identity_t<T> value,
+ const std::map<std::string, std::string, std::less<>>& valid_values, F callback)