我再次认真读了laravel issues的讨论, 还是没有明白, 主要是这句话
In order for the builder to not call newCollection twice, it would have to start passing Collections around under the hood.
看意思是如何避免调用两次newCollection, 不过怎么实现没有理解到
另外,我也看了laravel5.4的源码, 简单总结一下
builder->get方法入口
调用 getModels
再次调用了newCollection