'identifier' : illegal token on right side of '::'

If a class, structure, or union name appears to the left of the scope-resolution operator (double colons), the token on the right must be a class, structure, or union member. Otherwise, any global identifier can appear on the right.

The scope-resolution operator cannot be overloaded.

The following sample generates C2589:

// C2589.cpp  
void Test(){}  
class A {};  
void operator :: ();   // C2589  
  
int main() {  
   ::Test();  
}