add_rvalue_reference_t is an alias to the return type of add_rvalue_reference meta-function. Note, that the add_const_t avoids the ::type suffix and typename prefix when we want to use the result of the meta-function in templates.
Declared in <bslmf_addrvaluereference.h>
template<class t_TYPE>
using add_rvalue_reference_t = add_rvalue_reference<t_TYPE>::type;