g++ -std=c++17 vartest.cpp -o vartest && ./vartest; echo $?

vartest.cpp

#include <variant>
#include <string>
#include <cassert>

using std::string;

int main() {
    std::variant<bool, string> v = "hello";

    try {
        std::get<string>(v);
        return 0;
    }
    catch (const std::bad_variant_access&){
        return 1;
    }
}