The classkey or enum keyword present in the elaboratedtypespecifier shall agree in kind with the declaration to which the name in the elaboratedtypespecifier refers. This rule also applies to the form of elaboratedtypespecifier that declares a classname or friend class since it can be construed as referring to the definition of the class. Thus, in any elaboratedtypespecifier,the enum keyword shall be used to refer to an enumeration (7.2), the union classkey shall be used to refer to a union (clause 9), and either the class or struct classkey shall be used to refer to a class (clause 9) declared using the class or struct classkey.

Примечание classkey enum elaboratedtypespecifier - некоторые идентификаторы