In several of Simon Peyton Jones's presentations, there is a page which shows the history of Type Classes:
There are quite a lot of materials to understand type classes from a programmer's view, such as the typeclassopedia article and many other tutorials. However its implementation and overhead are seldom described.
I am wondering what were the problems during the implementations and their solutions (I think there should be academic publications for the solutions).
In other words, I am searching materials like Inside the C++ Object Model, but for the Haskell language.