Extract type system into a separate package?

[oprypkhantc]

Hey. Would the project be interested in extracting it's whole type system (alongside reflection) into a separate, semver'ed (even if the major version stays 0) composer package, like phpstan/type-system or two packages phpstan/types & phpstan/reflection, given I can my spend time doing that?

The reasoning for this is simple: practically anything that is acceptable magic, namely serialization, event handling, dependency injection, needs to have proper reflection and a proper type system behind it.

In PHP community it's currently done of the two ways:

1. don't support anything that isn't supported by the built-in reflection (so no generics, no intersection types, no type aliases)
2. implement own bulky type system (see jms/serializer)

PHPStan has a decent internal type system that isn't tightly bound with other parts of PHPStan and hence is also a relatively simple solution for the problem above.

My own use case for this is a serializer. It fully depends on being able to infer types and compare them. I'm currently using phpstan/phpstan-src alongside humbug/php-scoper to achieve this, but being able to simply depend on a library (which phpstan/phpstan-src is not) would make my life much easier.

Just moving the type system shouldn't be too hard. The only real nuance I encountered while implementing a serializer (and using phpstan/phpstan-src externally) is statically used Broker singleton in some of the types.

If there's any chance something like this could pass a pull request, I would be happy to help.

[ondrejmirtes]

Hi, this would complicate PHPStan's development by a lot so I don't have any plans to do this.