[krapp]

I was excited about Hack when it came out. Unfortunately PHP took just enough from it to kill it. I gave up on it once Composer stopped supporting it, after backwards compatibility with PHP no longer became a goal.

IMHO Hack's best feature was native support for XHP... which (also unfortunately) isn't something PHP decided to take.

[Twirrim]

Hack really gave PHP/Zend the kick up the arse that it seemed to need.

[eru]

I guess like Scala (et al) and Java? C++ also seems to be learning things from Rust these days.

[eru]

I only used Hack when I was very briefly working for Facebook. (And I used PHP once before nearly 20 years ago by now for some web site I had 'inherited', back when PHP was truly an awful language)