Tricky compilation error with __assume. Checked with VS2013 (/W4 /WX options enabled)

assumetest.cpp

#include <iostream>

struct A
{
	int n;
	A(int n) : n(n) {}
};

A Func(int n)
{
	if (n < 2)
	{
		return A(1);
	}
	else if (n >= 2)
	{
		return A(2);
	}
	else
	{
#if 1
		// OK
		//__assume(0);
		return A(3);
#elif 1
		// OK
		__assume(0);
		//return A(3);
#else
		// warning C4702, error C2220
		__assume(0);
		return A(3);
#endif
	}
}

int main()
{
	std::cout << Func(1).n << std::endl;
	return 0;
}