[girvo]

> When most practitioners think of "typechecking", they typically think about proving properties about programs statically. This project seems equivalent to adding a runtime check at each call site to ensure the arguments and return values are the correct type.

It basically seems equivalent (albeit somewhat nicer in a few ways, ie. scalar types are supported) to PHP's "type hinting"[0]. I will say that it is useful, in combination with unit testing, as you can pick up on problems with things slightly easier than hoping for the best in production and tailing error logs, but proper static type analysis is more useful.

[0] http://php.net/manual/en/language.oop5.typehinting.php

[foolfoolz]

editor support for php type hinting and phpdoc method comments goes a long way. intellij can do significant refactors and and searching. you'll get real time feedback for violating types. it's not quite the same as a explicit compile step but pretty close

[girvo]

Komodo IDE helps with that, but I personally switched to HHVM and have a simple bash script that swaps the `<?php` for `<?hh` and back, so that `hh_client` can statically tell me about problems, even when I'm not using any of the Hack features. Works a treat, to be honest!