std::experimental::ranges:: reference_t, std::experimental::ranges:: rvalue_reference_t, std::experimental::ranges:: iter_common_reference_t

From cppreference.com
template < class T >
concept bool /*dereferenceable*/ = requires ( T & t ) { { * t } - > auto && ; } ;
( exposition only* )
template < /*dereferenceable*/ T >
using reference_t = decltype ( * declval < T & > ( ) ) ;
(1) (ranges TS)
template < /*dereferenceable*/ T >

requires requires ( T & t ) { { ranges:: iter_move ( t ) } - > auto && ; }

using rvalue_reference_t = decltype ( ranges:: iter_move ( declval < T & > ( ) ) ) ;
(2) (ranges TS)
template < Readable T >

using iter_common_reference_t = ranges:: common_reference_t < ranges :: reference_t < T > ,

ranges :: value_type_t < T > & > ;
(3) (ranges TS)
1) Obtain the reference type of a dereferenceable type T .
2) Obtain the rvalue reference type of a dereferenceable type T , that is, the return type of ranges::iter_move .
3) Compute a Readable type's common reference type . This is the common reference type of its reference type and an lvalue reference to its value type.

Notes

The - > auto && constraint checks that the type of the expression is not void .