Written by Michael Larabel in Free Software on 28 August 2019 at 06:30 AM EDT.

Facebook's HHVM implementation that started off as a high performance PHP5 implementation but is now just focused on powering their own Hack programming language is beginning to see some of its code rewritten in Rust.

HHVM 4.20 was released on Tuesday and with this release they have been transitioning some of their code from OCaml to Rust.

The initial code rewritten in Rust is the HHVM/Hack parser and can be optionally enabled via their INI configuration file.

This Rust'ed parser should be at parity to their existing parser albeit now with greater memory safety and other benefits of Rust. The INI tunable for enabling the Rust-written parser on HHVM 4.20 and later is hack.lang.hack_compiler_use_rust_parser=1.

More details on the new HHVM 4.20 release at HHVM.com.

Ref: https://www.phoronix.com/scan.php?page=news_item&px=Facebook-Rust-HHVM&from=singlemessage