Can a template parameter be both an int and an unsigned long?

Question

I have the following code:

#include <iostream>

template<size_t N>
class A
{
};

template<int N, typename T> class B;

template<int N>
class B<N, A<N>>
{
};

int main()
{
    B<3, A<3>> b;
    return 0;
}

Here, B is templated on an int while A is templated on size_t, which is an unsigned long with both compilers I am using.

When I use compiler 1 (current compiler), everything compiles and works the way I expect it to. When using compiler 2 (one we're moving to), I get a compiler error stating that there is no template specialization for B that takes an unsigned long - it has interpreted the 3 as an unsigned long as it needs to be one for A, but then can't find anything for B. The fix is obvious, - just change B to take a size_t as well (or change A to take an int) - but I was wondering which is strictly correct by the standard. My gut feel is that it's compiler 2 (the one that's throwing the error).

Answer 1

From [temp.deduct.type]:

If P has a form that contains <i>, and if the type of i differs from the type of the corresponding template parameter of the template named by the enclosing simple-template-id, deduction fails.

A<N> for N is an int should fail deduction because the corresponding template parameter of A is actually size_t. This is a compiler #1 bug.