something.cc

#include <stdio.h>

template <int x_init, int y_init>
class HasStructures {
 public:
  struct InnerStruct {
    InnerStruct(): x(x_init), y(y_init) {}
    int x;
    int y;
  };
  static InnerStruct item;
};

template <int x_init, int y_init>
HasStructures<x_init, y_init>::InnerStruct HasStructures::item;

int main() {
  printf("%d, %d\n", HasStructures<5, 6>::item.x, HasStructures<5, 6>::item.y);
  return 0;
}