[iterator.cust.move]

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

The expression ranges::iter_move(E) for a subexpression E is expression-equivalent to:

(1.1)
iter_move(E), if E has class or enumeration type and iter_move(E) is a well-formed expression when treated as an unevaluated operand, where the meaning of iter_move is established as-if by performing argument-dependent lookup only ([basic.lookup.argdep]).
(1.2)
Otherwise, if the expression *E is well-formed:
- (1.2.1)
  if *E is an lvalue, std::move(*E);
- (1.2.2)
  otherwise, *E.
(1.3)
Otherwise, ranges::iter_move(E) is ill-formed.

[Note 1:
This case can result in substitution failure when ranges::iter_move(E) appears in the immediate context of a template instantiation.
— end note]

25 Iterators library [iterators]