Can I have a template constructor inside a template class?

JUANDENT (411)
Hi,


This does not compile but it should since other is an instance of a class template which inherits from CheckingPolicy<T2>

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template
<
	typename T,
	template<typename> class CheckingPolicy
>
struct SmartPtr : public CheckingPolicy<T>
{
	SmartPtr(T* p = nullptr) : pointee{ p } {  }

	template<typename T2, template<typename> class CP2>
	SmartPtr(const SmartPtr<T2, CP2>& other)
		:  CheckingPolicy<T2>( other)
	{
		auto pCPT2 = static_cast<CheckingPolicy<T2>*>(&other);
	}

	template<typename T2, template<typename> class CP2>
	friend struct SmartPtr;

};


The rest of the code is:

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/// ChekingPolicies
/// </summary>
/// <typeparam name="T"></typeparam>
template<typename T>
struct NoChecking
{
	NoChecking() = default;
	template<typename T2>
	NoChecking(const NoChecking<T2>& other)
	{}
	static void Check(T*) {}
};

template<typename T>
struct EnforceNotNull
{
	EnforceNotNull() = default;
	template<typename T2>
	EnforceNotNull(const EnforceNotNull<T2>& other)
	{}
	static void Check(T* p)
	{
		if (!p)
			throw std::exception{ "Null Pointer Exception" };
	}
};

struct Sample
{};

void usePolicy()
{
	SmartPtr<Sample, EnforceNotNull> spSample(new Sample);

         // copy constructor:
	SmartPtr<Sample, NoChecking> spSample2(spSample);

}



The error is:


'static_cast': cannot convert from 'const SmartPtr<Sample,EnforceNotNull> *' to 'NoChecking<T> *'




What is going on?

Regards,
Juan
helios (17574)
One is a pointer to const and the other is a pointer to non-const.
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