Also, I'm very curious: how does the KLOC count compare for the PHP and Rust versions?
While I don't think you can beat straight php/js/python for this, there's still a lot of room for improvement over the rust/c++ magnitude of compile times.
For example Go/OCaml/Common Lisp (at least, SBCL is a compiler, there are lisp interpreters), all have reasonably quick compile times. And the latter two have repls, which really does help improve the iteration cycle.
I haven't had to play with crystal, where does it fall on this spectrum?
I don't have exact numbers since it's not a straight port — the original PHP code was written to analyse a slightly different language than the Rust version I'm building.
I'd estimate that Rust requires you to be about 10% more verbose than PHP. Main annoyances vs PHP: no default argument values, and only a single let allowed inside an if conditional.