Overriding Overloaded Functions

As with any other function, a member function (virtual or otherwise) can be overloaded. A derived class can override zero or more instances of the overloaded functions it inherits. If a derived class wants to make all the overloaded versions available through its type, then it must override all of them or none of them.

Sometimes a class needs to override some, but not all, of the functions in an overloaded set. It would be tedious in such cases to have to override every base-class version in order to override the ones that the class needs to specialize.

Instead of overriding every base-class version that it inherits, a derived class can provide a using declaration (§15.5, p. 615) for the overloaded member. A using declaration specifies only a name; it may not specify a parameter list. Thus, a using declaration for a base-class member function adds all the overloaded instances of that function to the scope of the derived class. Having brought all the names into its scope, the derived class needs to define only those functions that truly depend on its type. It can use the inherited definitions for the others.

The normal rules for a using declaration inside a class apply to names of overloaded functions (§15.5, p. 615); every overloaded instance of the function in the base class must be accessible to the derived class. The access to the overloaded versions that are not otherwise redefined by the derived class will be the access in effect at the point of the using declaration.