原文:This goes wrong of course when the original value items are not unique; in that case no error occurs, but the processing of the inverted map is simply stopped when a nonunique key is encountered, and it will most probably not contain all pairs from the original map!
我觉得这一句应该是因为编译器这种情况下不会报错才特地提醒的
虽然原文的这个句式有点让人费解...