std::variant reflection. How can I tell which type of value std::variant is assigned?

If you only need to ask “Is this variant of type X ?” for a single type X, then I recommend that you prefer std::holds_alternative over std::variant::index because the line of code is easier to read and will not have to be updated if the index of the type in the variant changes in the future.

Example:

if (std::holds_alternative<X>(my_variant)) {
    std::cout << "Variant is of type X" << std::endl;
}