14 If a variable member of a namespace is defined outside of the scope of its namespace then any name that appears in the definition of the member (after the declarator-id) is looked up as if the definition of the member occurred in its namespace.

#include <iostream>

namespace N1
{
   namespace N2
   {
       int i = 10;
   }

using namespace N2;

   namespace N3
   {
       extern int x;
}

   inline namespace N4
   {
       int j = 20;
   }
}

int i = 1;
int j = 2;

int N1::N3::x = i + j;

int main()
{
std::cout << "N1::N3::x = " << N1::N3::x << '\n';
}

The MS Visual C++ 2019 produces the following result

N1::N3::x = 30

So several questions arise. The first one is the program valid? That is are the variable declarations

int i = 1;
int j = 2;

are visible in the this declaration

int N1::N3::x = i + j;

That is if the definition «occurs» in the namespace (according to the quote) then the names are not visible. If I am wrong then should the value of the variable x be equal to 12? Is it a bug of the compiler that outputs the value of x equal to 30?

With best regards,

(Vlad from Moscow)