odd vs warning: cl.exe main.cpp /W4

main.cpp

struct foo
{
    template<typename... Args>
    void operator[](Args&&...)	
    {
    }
};

struct bit {};
 
int main()
{
   foo f;
  
   f[
      bit()     // warning C4709: comma operator within array index expression
   ];
   return 0;
}