Base class template instantiation depending on derived class constructor argument type

In the following, shouldn't base class constructor be generated by the compiler based on derived class constructor a开发者_开发百科rgument type?

template <class T>
class foo
{
int a;
public:
    foo(T a){}
    // When I convert the constructor to a function template, it works fine.
    // template <typename T> foo(T a){}
};

class bar : public foo<class T>
{
public:
    bar(int a):foo(a){}
};

int main(void)
{
    bar obj(10);
    system("pause");
    return 0;
}

error C2664: 'foo::foo(T)' : cannot convert parameter 1 from 'int' to 'T'

I understand the error, but why is that ?

The syntax in class bar : public foo<class T> is incorrect.

• Either bar depends on a template parameter T and bar should be a template :

  template<class T>
  class bar : public foo<T>
  {
  public:
      bar(int a):foo(a){}
  };
  
  
  int main()
  {
      bar<int> obj(10);
  }
  

• Or you want bar to inherit from a specific instantiation of foo such as :

  class bar : public foo<int>
  {
  public:
      bar(int a):foo(a){}
  };
  
  
  int main()
  {
      bar obj(10);
  }