add_const_t add_lvalue_reference_t add_pointer_t add_rvalue_reference_t async async async async atom begin bit_cast common_type_t conditional_t decay_t effect_result_t empty enable_if_t end exchange fallback getenv getenv ignore in_place index_sequence invoke invoke_result_t iota_diff_t iter_category_t iter_difference_t iter_reference_t iter_value_t iterator_t make_filter_iterator make_index_iterator make_index_sequence make_iota_iterator make_optional make_optional make_optional make_overload make_signed_t make_subrange make_transform_iterator make_unique make_unsigned_t midpoint midpoint nameof nameof nullopt of_string operator!= operator!= operator!= operator!= operator!= operator< operator< operator< operator< operator< operator<= operator<= operator<= operator<= operator<= operator== operator== operator== operator== operator== operator> operator> operator> operator> operator> operator>= operator>= operator>= operator>= operator>= range_difference_t range_reference_t range_size_t range_value_t remove_const_t remove_cv_t remove_cvref_t remove_extent_t remove_pointer_t remove_reference_t size to_string to_unsigned transform tuple_element_t type_identity_t void_t

nullopt nullopt_t halcheck::lib::nullopt {nullopt_t::tag{}} staticconstexpr An implementation of std::nullopt. See also std::nullopt