cpp/experimental/ranges/iterator/dangling

The class template is a simple wrapper around an object to indicate that the wrapped object may be dangling, that is, it refers to another object whose lifetime may have ended.

The alias template returns the iterator type of, wrapped in  if the range was an rvalue range (as indicated by  not being an lvalue reference type).

They are used by range algorithms that accept rvalue ranges and return iterators into them.