c++ issue with template class inheritance - c++

Question

I'm getting an error when compiling a code that can be trivialized as follows:
#include<iostream>
template <class T>
class A
{
protected:
T protectedValue;
template<class TT>
class insideClass
{
public:
TT insideClassValue;
};
};
template<class T>
class B : public A<T>
{
public:
void print(T t)
{
insideClass<T> ic; // <-- the problem should be here
ic.insideClassValue = t;
std::cout << ic.indideClassValue << std::endl;
};
};
int main()
{
double v = 2.;
B<double> b;
b.print(v);
return 0;
};
The compiler (g++) gives the following error:
main.C: In member function ‘void B<T>::printA()’:
main.C:23:4: error: ‘insideClass’ was not declared in this scope
main.C:23:17: error: expected primary-expression before ‘>’ token
main.C:23:19: error: ‘ic’ was not declared in this scope
I figured out that if class A is not a template class, the compilation will not give any error.
I do not understand why making class A a template class results in the described error.
Any idea about the reasons and how to fix the problem?

Answer 1

Without qualification insideClass is a non-dependent name which is looked up during phase 1 look-up. Since the definition of the base depending on a template argument isn't known, names from the base class are ignored and the name isn't found. Qualification and possibly adding typename in a strategic place should solve the problem (thanks to remyabel for the notation):
typename A<T>::template insideClass<T> ic;
The template keyword is needed to indicate that what's coming is a template and the typename is needed to indicate that happens to be a type. Getting the correct spelling of what a dependent name is supposed to be is sometimes not entirely straight forward. A SSCCE showing the problem is here and the solution is here.

Answer 2

Something like this:
typedef typename A<T>::template insideClass<T> ic;
public:
void print(T t)
{
ic ic;
ic.insideClassValue = t;
std::cout << ic.insideClassValue << std::endl;
};