Unintentional typecast that causes infinite recursive loop

bug-infinite-recursion-accidental-automatic-typecast.cpp

// clang++ -Wall -std=c++11 -O0 -o test test.cpp && ./test
// g++ -Wall -std=c++11 -O0 -o test test.cpp && ./test

#include <iostream>
#include <vector>
#include <cstdio>

namespace Ns
{

struct Foo;
std::ostream& operator<<(std::ostream& os, const Foo& x) { return os; }

struct Foo
{
   // TO PREVENT accidental type conversion add "explicit"
   // - for consideration: all non-explicit constructors with single parameter may trigger this problem 
   Foo(std::vector<int> i)
   {
      printf("HEHEE\n");
      std::cout << i;
   }
};

}

int main(int, char*[])
{
   Ns::Foo obj{{}};
   
   return 0;
}