class-name: identifier simple-template-id
class-specifier: class-head { member-specificationopt }
class-head: class-key attribute-specifier-seqopt class-head-name class-virt-specifieropt base-clauseopt class-key attribute-specifier-seqopt base-clauseopt
class-head-name: nested-name-specifieropt class-name
class-virt-specifier: final
class-key: class struct union
member-specification: member-declaration member-specificationopt access-specifier : member-specificationopt
member-declaration: attribute-specifier-seqopt decl-specifier-seqopt member-declarator-listopt ; function-definition using-declaration static_assert-declaration template-declaration alias-declaration empty-declaration
member-declarator-list: member-declarator member-declarator-list , member-declarator
member-declarator: declarator virt-specifier-seqopt pure-specifieropt declarator brace-or-equal-initializeropt identifieropt attribute-specifier-seqopt : constant-expression
virt-specifier-seq: virt-specifier virt-specifier-seq virt-specifier
virt-specifier: override final
pure-specifier: = 0