Consider https://godbolt.org/z/5xKWK9G5o
namespace icl = boost::icl;
int main()
{
icl::interval_set<uint8_t> i8;
i8.insert(std::numeric_limits<uint8_t>::max());
fmt::print("cardinality={}", cardinality(i8));
}
this prints cardinality=18446744073709551361 .
The issue is the cardinality() at concept/interval.hpp which uses last_next(object) which overflows to 0, in this case.
With interval_set, things would be worse, since these overflows would be undefined behavior.
I suggest removing the use of last_next in any situation where the interval may be the biggest interval in the set.