Hack layered a sane type system on the existing runtime, but the changes above are all about runtime logic. These type coercions lead to many subtle bugs in PHP

Hack layered a sane type system on the existing runtime, but the changes above are all about runtime logic. These type coercions lead to many subtle bugs in PHP programs. What this demonstrates is that one can have a much safer programming language while keeping the key attributes of PHP that make it great: each web request having isolated state, concurrency model, and programmer workflow (ref. https://slack.engineering/taking-php-seriously-cf7a60065329 https://slack.engineering/taking-php-seriously-cf7a60065329). Yes, I'm not necessarily advocating for any web developer to start building in Hack now -- mainly because it lacks PHP's rich ecosystem. The good folks working on the PHP language may be interested in these changes though.