Does this presentation match the current version of Hack fairly well? It has a nice explanation of the type system that is more concise than the one on the web

Does this presentation match the current version of Hack fairly well? It has a nice explanation of the type system that is more concise than the one on the web site. https://raw.github.com/strangeloop/StrangeLoop2013/master/slides/sessions/Adams-TakingPHPSeriously.pdf https://raw.github.com/strangeloop/StrangeLoop2013/master/sl... The idea of bolting a static checker onto a dynamic language and using an unresolved top type to make it work is cool. The presentation refers to your system as SoA gradual typing. Are there any papers or presentations which explain that approach and how it works in more detail? Particularly in how it might differ from gradual typing?