Support narrowing down array_filter return type via string callable

[herndlm]

Closes phpstan/phpstan#6417

[staabm]

Separate test-cases for

• a string which is not callable
• A string to a class-method reference
• With a 3rd mode arg

would be useful

[herndlm]

adapted. what do you think? unfortunately narrowing-down the return type is currently only working for built-in functions. not entirely sure if this is a normal phpstan limitation or not. and/or if I could add support for it 🤔 you'll understand what I mean if you take a look at the last block of tests.

Basically I need to get the return statement and its expression of a function/method and use that instead. Did not find a way to achieve that yet.

[ondrejmirtes]

I think this is fine, feel free to mark it as ready :)

[herndlm]

Guess you also don't have a simple solution for the following?

Basically I need to get the return statement and its expression of a function/method and use that instead. Did not find a way to achieve that yet.

[ondrejmirtes]

The logic in some type-specifying extensions can be really complex making it impossible to rewrite it in AST.

[ondrejmirtes]

Thank you!