看起来g++ 4.8 正在获得自动返回类型扣除的实现。
这个补丁是由Jason Merrill放入的，他也为C ++ - 1Y发送了一个论文。此功能可以使用-std = c ++ 1y。

It would appear that g++ 4.8 is getting an implementation of auto return type deduction. The patch was put in by Jason Merrill who is also sending a paper for C++-1Y for the feature. The feature is available with -std=c++1y.

仍在使用它。