内置类型的赋值运算返回对右（还是左？？）操作数的引用

C/C++ code

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.赋值操作符的返回类型应该与内置类型赋值运算返回的类型相同（第 5.4.1 节）。内置类型的赋值运算返回对[color=#FF0000]右[/color]操作数的引用，因此，赋值操作符也返回对同一类类型的引用。

C++primer 中文版 P411写的是“内置类型的赋值运算返回对右操作数的引用”。

“left-hand operand.”这个是做操作数吧,什么情况？

[解决办法]
returns a reference to its left-hand operand
left是左，这段话里哪有右了