View source for cpp/language/member template

===Conversion function templates===
A user-defined {{rlp|cast operator|conversion function}} can be a template.

{{source|1=
struct A
{
    template<typename T>
    operator T*(); // conversion to pointer to any type
};

// out-of-class definition
template<typename T>
A::operator T*() { return nullptr; }

// explicit specialization for char*
template<>
A::operator char*() { return nullptr; }

// explicit instantiation
template A::operator void*();

int main()
{
    A a;
    int* ip = a.operator int*(); // explicit call to A::operator int*()
}
}}

During {{rlp|overload resolution}}, specializations of conversion function templates are not found by {{rlp|lookup|name lookup}}. Instead, all visible conversion function templates are considered, and every specialization produced by {{rlp|template argument deduction}} (which has special rules for conversion function templates) is used as if found by name lookup.

Using-declarations in derived classes cannot refer to specializations of template conversion functions from base classes.

{{rrev|since=c++14|{{mark unreviewed dr|CWG|1878}}
A user-defined conversion function template cannot have a deduced return type:
{{source|1=
struct S
{
    operator auto() const { return 10; } // OK
    template<class T> operator auto() const { return 42; } // error
}; 
}}
}}

{{rrev|since=c++14|
===Member variable templates===
A variable template declaration may appear at class scope, in which case it declares a static data member template. See {{rlp|variable template}}s for details.
}}