It only warns if the assignment doesn't have an extra pair of parentheses. These were added in this case, to silence the warning (so the attack would not be no

It only warns if the assignment doesn't have an extra pair of parentheses. These were added in this case, to silence the warning (so the attack would not be noticed). The parentheses are also needed in this case to get the precedence right, but they won't be needed if '==' were written, so anyone coding this by accident would immediately be warned of the mistake.