in cxx/fbjni/detail/SimpleFixedString.h [234:245]
constexpr SimpleFixedString(const SimpleFixedString<M>& that, std::size_t pos, std::size_t count) noexcept(false)
: SimpleFixedString{
that.data_,
that.size_,
std::make_index_sequence<(M < N ? M : N)>{},
pos,
detail::fixedstring::checkOverflow(
detail::fixedstring::checkOverflowOrNpos(
count,
that.size_ -
detail::fixedstring::checkOverflow(pos, that.size_)),
N)} {}