https://www.ctolib.com/topics-115290.html
但是还是用到了一个叫做 The Protocol Witness Table (PWT) 的函数表
https://blog.csdn.net/Hello_Hwc/article/details/53147910
https://academy.realm.io/posts/goto-mike-ash-exploring-swift-memory-layout/
原文：https://www.cnblogs.com/feng9exe/p/9676652.html