I'd also add to this that PureScript[1] is soon to have a Lua backend[2]. PureScript is a statically typed language with row polymorphic types, algebraic effects and type inference.

[1]: http://purescript.org [2]: https://github.com/osa1/psc-lua

People interested in experimental Lua type systems might also want to check out Typed Lua, André Maidl's ongoing dissertation project. He will be doing a presentation soon at the Dyla workshop:

http://www.lifl.fr/dyla14/

Looks good, but the syntax is ugly, and sol uses a much nicer type syntax and allows definitions of subtypes already.

https://github.com/emilk/sol

Serious question, why link to a year old email to an email list?

I get that type systems and type checking have been a hot topic recently... but why this?

Well, its interesting is it not? Fabien has some nice language .. I was comfortably reminded of a stack of stuff from Felleisen that I still haven't got through, and should read instead of reading HN .. and actually Lua has a few fronts in the effort to make type- systems of different variety available to those that need it, so why not discuss it?

From that perspective, its an interesting article. If, like me, you're a fan of Lua as a general purpose platform for a lot of things, seeing the ease with which the grand masters tackle thornier issues .. its interesting, but also inspiring.