this talk and the referenced pair talk by matt bauman were really excellent.

basically the big takeaway that i walked away with was that they defined a sort of pseudoclosure in the guts of the language before the compiler which relaxes some of the behaviors of a closure (ie what gets captured) which then enables the creation of larger optimizable regions for the compiler in the context of doing autodiff.

the demo by matt bauman where they do autodiff on a function that prompts for and has the user type in the name of another julia mathematical function was really impressive!