gistfile1.txt

#include <iostream>

namespace ns1 {
  template <typename T, typename U>
  int operator+(const T&, const U&) 
  {
    std::cout << "ns1::operator+" << std::endl;
    return 1;
  }

  namespace ns1_1 {

    using ns1::operator+;

    struct foo {
    };  

  }


  namespace ns1_2 {

    struct bar {}; 

    bar operator+(const bar&, const bar&)
    {   
      std::cout << "ns1_2::operator+" << std::endl;
    }   

    int function()
    {   
      ns1_1::foo a, b;

      a + b;
    }   
  }
}

int main() {
}