Conditional return type for container

[snapshotpl]

Bug report

I'd like to create stub for Container with conditional return type, however looks like is not possible to do that because bug or missing feature.

Code snippet that reproduces the problem

https://phpstan.org/r/b559c7cd-8851-4953-a7ec-0d8b5b3cc714

Expected output

No error and correct type

[ondrejmirtes]

class-string<T>|string gets normalized to string: https://phpstan.org/developing-extensions/type-system#type-normalization

But I think we might make this version work: https://phpstan.org/r/233f9fb4-884a-4d35-8807-66aa281c067b

WDYT @rvanvelzen ?

[snapshotpl]

Your version looks better, but my works on psalm 🤔

[rvanvelzen]

To me it seems better to keep templated types when normalizing, which should make the original case work. I.e. string|class-string ⇒ string but string|class-string<T> ⇒ string|class-string<T>.

That being said, inferring from conditional types would be nice too.

[ondrejmirtes]

I worry it’s not possible, string type contains all class-strings, even with generics. Changing that could break a lot of assumptions. But feel free to try it 😊

[rvanvelzen]

class-string<T> with an unbounded T is always a super type of a constant string, so the provided tests won't work as expected using ($id is class-string<T> ? T : mixed)syntax - it will always returnT`.

[ondrejmirtes]

I think that we can make https://phpstan.org/r/233f9fb4-884a-4d35-8807-66aa281c067b work - ($id is class-string<T> ? T : mixed) is (string is class-string<T> ? T : mixed) so there shouldn't be an issue.

[zonuexe]

I got here from #7513.

This issue is very inconvenient for the general use case of PHP container libraries, but I agree that the phpstan/phpstan-src#1459 and phpstan/phpstan-src#1262 approaches are ugly hacks that make supertypes inconsistent.

#7141 (comment) looks like a good way to do it. However, we also note that @param is not only machine-readable, but also human-friendly documentation.

[ondrejmirtes]

Implemented by phpstan/phpstan-src#1465

[staabm]

the initial example has less errors, but the return type seems still wrong?

https://phpstan.org/r/2210407c-a794-4637-8781-ffc19bd6d7a3

[ondrejmirtes]

Only the one without @param is supposed to work.

[snapshotpl]

Awesome! Great job!

[github-actions]

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