code: private int referenceKind(Symbol refSym) {
          if (refSym.isConstructor()) {
              return ClassFile.REF_newInvokeSpecial;
          } else {
              if (refSym.isStatic()) {
                  return ClassFile.REF_invokeStatic;
              } else if ((refSym.flags() & PRIVATE) != 0) {
                  return ClassFile.REF_invokeSpecial;
              } else if (refSym.enclClass().isInterface()) {
                  return ClassFile.REF_invokeInterface;
              } else {
                  return ClassFile.REF_invokeVirtual;
              }
          }
      }
docs: Get the opcode associated with this method reference