An identifier expression, or id-expression, is a restricted form of primary expression. Syntactically, an id-expression requires a higher level of complexity than a simple identifier to provide a name for all of the language elements of C++.
An id-expression can be either a qualified or unqualified identifier. It can also appear after the dot and arrow operators.
Identifier expression syntax >>-+-| unqualified_id |-+-------------------------------------->< '-| qualified_id |---' unqualified_id |--+-identifier-------------+-----------------------------------| +-operator_function_id---+ +-conversion_function_id-+ +-~--class_name----------+ '-template_id------------' qualified_id |--+-::--+-identifier-----------+-------------------------------------------------------------------------------+--| | +-operator_function_id-+ | | '-template_id----------' | | .------------------------------------------. | | V | | '-+----+----+--------------------------------------+-+--class_or_namespace--::--+----------+--unqualified_id-' '-::-' '-class_or_namespace--::--+----------+-' '-template-' '-template-'