62   template<class _I2, class _S2>
63     requires convertible_to<const _I2&, _Iter> && convertible_to<const _S2&, _Sent>
64   constexpr common_iterator(const common_iterator<_I2, _S2>& __other)  in common_iterator()  argument
72   template<class _I2, class _S2>
73     requires convertible_to<const _I2&, _Iter> && convertible_to<const _S2&, _Sent> &&
74              assignable_from<_Iter&, const _I2&> && assignable_from<_Sent&, const _S2&>
75   common_iterator& operator=(const common_iterator<_I2, _S2>& __other) {
109   template<class _I2 = _Iter>
111     requires indirectly_readable<const _I2> &&
112     (requires(const _I2& __i) { __i.operator->(); } ||
113      is_reference_v<iter_reference_t<_I2>> ||
114      constructible_from<iter_value_t<_I2>, iter_reference_t<_I2>>)
148   template<class _I2, sentinel_for<_Iter> _S2>
149     requires sentinel_for<_Sent, _I2>
150 …friend constexpr bool operator==(const common_iterator& __x, const common_iterator<_I2, _S2>& __y)…
163     return _VSTD::__unchecked_get<_Sent>(__x.__hold_) == _VSTD::__unchecked_get<_I2>(__y.__hold_);
166   template<class _I2, sentinel_for<_Iter> _S2>
167     requires sentinel_for<_Sent, _I2> && equality_comparable_with<_Iter, _I2>
168 …friend constexpr bool operator==(const common_iterator& __x, const common_iterator<_I2, _S2>& __y)…
179 …   return  _VSTD::__unchecked_get<_Iter>(__x.__hold_) ==  _VSTD::__unchecked_get<_I2>(__y.__hold_);
184     return _VSTD::__unchecked_get<_Sent>(__x.__hold_) ==  _VSTD::__unchecked_get<_I2>(__y.__hold_);
187   template<sized_sentinel_for<_Iter> _I2, sized_sentinel_for<_Iter> _S2>
188     requires sized_sentinel_for<_Sent, _I2>
189 …friend constexpr iter_difference_t<_I2> operator-(const common_iterator& __x, const common_iterato…
200       return  _VSTD::__unchecked_get<_Iter>(__x.__hold_) - _VSTD::__unchecked_get<_I2>(__y.__hold_);
205     return _VSTD::__unchecked_get<_Sent>(__x.__hold_) - _VSTD::__unchecked_get<_I2>(__y.__hold_);
216   template<indirectly_swappable<_Iter> _I2, class _S2>
217   friend constexpr void iter_swap(const common_iterator& __x, const common_iterator<_I2, _S2>& __y)  in iter_swap()  argument
218       noexcept(noexcept(ranges::iter_swap(declval<const _Iter&>(), declval<const _I2&>())))  in iter_swap()
221 …_LIBCPP_ASSERT(holds_alternative<_I2>(__y.__hold_), "Attempted to iter_swap a non-dereferenceable …  in iter_swap()
222 …return ranges::iter_swap(_VSTD::__unchecked_get<_Iter>(__x.__hold_), _VSTD::__unchecked_get<_I2>(_…  in iter_swap()