I just had finished an article about facebooks new programming language. I am compiling it right now (thats there is a aur package available for hhvm).
In general, it looks like hack is
friendship php with benefits. Can be run as script language, can be used as dynamically typed. Yes you are right, both times a "can be", indicating "can run as compiled code" and "can be statically typed" (or how they called it gradual typing.
So what hack is hack?
Hack is a programming language for HHVM that interoperates seamlessly with PHP. Hack reconciles the fast development cycle of PHP with the discipline provided by static typing, while adding many features commonly found in other modern programming languages.
Hack provides instantaneous type checking via a local server that watches the filesystem. It typically runs in less than 200 milliseconds, making it easy to integrate into your development workflow without introducing a noticeable delay.
Good articles are starting to spreading around, first i found was on sitepoint.com.
I was searching for a support announcement of hack for phpstorm and yes, there is a feature request for hack support as well as a feature request for hvvm debugger out there. Crossing fingers to get it in asap .