Propagating 'typedef' from based to derived class for 'template'

c++ templates inheritance typedef name-lookup
dimba picture dimba · Oct 29, 2009 · Viewed 29.9k times · Source

I'm trying to define base class, which contains typedef's only. 

template<typename T>
class A
{
public:
    typedef std::vector<T> Vec_t;
};


template<typename T>
class B : public A<T>
{
private:
    Vec_t v;  // fails - Vec_t is not recognized
};

Why in B I receive an error that Vec_t is not recognized and I need to write it explicitly?

typename A<T>::Vec_t v;

Answer

Kirill V. Lyadvinsky picture Kirill V. Lyadvinsky · Oct 29, 2009

I believe that this question is duplicate, but I cannot find it now. C++ Standard says that you should fully qualify name according to 14.6.2/3:

In the definition of a class template or a member of a class template, if a base class of the class template depends on a template-parameter, the base class scope is not examined during unqualified name lookup either at the point of definition of the class template or member or during an instantiation of the class template or member.

UPD: I found duplicate finally: here it is.

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