[range.access.rend]

The name ranges::rend denotes a customization point object ([customization.point.object]).

Given a subexpression E with type T, let t be an lvalue that denotes the reified object for E.

Then:

(2.1)
If E is an rvalue and enable_borrowed_range<remove_cv_t<T>> is false, ranges::rend(E) is ill-formed.
(2.2)
Otherwise, if T is an array type ([basic.compound]) and remove_all_extents_t<T> is an incomplete type, ranges::rend(E) is ill-formed with no diagnostic required.
(2.3)
Otherwise, if decay-copy(t.rend()) is a valid expression whose type models sentinel_for<decltype(ranges::rbegin(E))> then ranges::rend(E) is expression-equivalent to decay-copy(t.rend()).
(2.4)
Otherwise, if T is a class or enumeration type and decay-copy(rend(t)) is a valid expression whose type models sentinel_for<decltype(ranges::rbegin(E))> with overload resolution performed in a context in which unqualified lookup for rend finds only the declarations
```
void rend(auto&) = delete;
void rend(const auto&) = delete;
```
then ranges::rend(E) is expression-equivalent to decay-copy(rend(t)) with overload resolution performed in the above context.
(2.5)
Otherwise, if both ranges::begin(t) and ranges::end(t) are valid expressions of the same type which models bidirectional_iterator ([iterator.concept.bidir]), then ranges::rend(E) is expression-equivalent to make_reverse_iterator(ranges::begin(t)).
(2.6)
Otherwise, ranges::rend(E) is ill-formed.