Feature request

Many frameworks provide ways of dynamically loading props & methods into a class at runtime (essentially a runtime trait).

E.g., Yii Behaviors: https://www.yiiframework.com/doc/guide/2.0/en/concept-behaviors

This becomes inherently difficult for any static tooling (eg IDEs, PHPStan) to know about these additional class members.
Normally this means you need to create stubs.

@mixin isn't an option, as the classes we're referring to are libraries/Composer packages.

My proposal is to support something like @mixin-to \some\ns\SomeClass that could be added to either classes or class members to add those members to the referenced entity.