if-this-is alternative?

[devnix]

Hi! I'm trying to contribute to a library with a new method of a class with a generic.

If this method is called, the object's generic is a tuple of two known values, and we will want to return both values.

This library is currently psalm-only compliant, although I've made some contributions to improve the compatibility with PHPStan from a library consumer PoV. In psalm annotations, I think I've been able to achieve what we want: https://psalm.dev/r/b7e175d161

But in PHPStan I can't find a way to tell the static analysis how to hydrate the templates of the unzip method: https://phpstan.org/r/43878041-d2c6-4be6-aa1a-545fed407c9e

Is there any other way to type this, or is it just a missing feature for now?

[ondrejmirtes]

Hello, how do yo understand the purpose of @psalm-if-this-is? From the docs: https://psalm.dev/docs/annotating_code/adding_assertions/

// IfThisIsMismatch - Class is not a<int> as required by psalm-if-this-is

Looks like that when the object isn't a<int>, the method is not allowed to be called.

But your use-case is different. Can you describe it in more detail?

[devnix]

This is the implementation of what I'm working on: https://github.com/azjezz/psl/pull/434/files#diff-2f0aface51740d421d0dfff2e9555aa045cb4e0417892df29fd3747f98f3d436R354-R362

In an Option<array{A,B}> I'm implementing a method to separate it in array{Option<A>,Option<B>}. After trying out a lot of things I found @psalm-if-this-is. Indeed it works as a check that you are calling a method only if a condition is given, but it has another effect in my example: it makes me able to fill those two templates.

[ondrejmirtes]

I feel like this should be a different feature for this purpose instead of misusing if-this-is tag for this scenario.

Please try to replicate this in a different language like TypeScript or Hacklang, and open a feature request, thank you.

[devnix]

Here's the feature request with a working Hacklang example 🙂 #10296