原文是:
The return type from the assignment operator should be the same as the return from assignment for the built-in types (Section 5.4.1, p. 160). Assignment to a built-in type returns a reference to its left-hand operand. Therefore, the assignment operator also returns a reference to the same type as its class.
其中第二句
Assignment to a built-in type returns a reference to its “left-hand” operand.