24 Ranges library [ranges]

24.3 Range access [range.access]

24.3.12 ranges​::​data [range.prim.data]

The name ranges​::​data 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:
[Note:
Diagnosable ill-formed cases above result in substitution failure when ranges​::​data(E) appears in the immediate context of a template instantiation.
— end note]
[Note:
Whenever ranges​::​data(E) is a valid expression, it has pointer to object type.
— end note]