Incorrect return type when calling unique on an Eloquent Collection

[Daanra]

• Larastan Version: 0.6.4
• PHPStan Version: 0.12.42
• --level used: max

Description

When calling unique() on an Eloquent Collection (or a custom Collection class), the return type is inferred as Illuminate\\Support\\Collection, however, this is incorrect.

Laravel's PHPDoc seems to be correct, and it doesn't seem like we're overriding it with a stub. So I'm unsure why this is happening.

Laravel code where the issue was found

use Illuminate\Database\Eloquent\Collection as EloquentCollection;

// ...

public function testCollectionUnique(EloquentCollection $collection): EloquentCollection
{
    return $collection->unique();
}

Error output:

Method Tests\\Features\\ReturnTypes\\CustomEloquentCollectionTest::testCollectionUnique() should return Illuminate\\Database\\Eloquent\\Collection but returns Illuminate\\Support\\Collection.

[canvural]

I think the return type in Laravel is wrong. It should be just static There is no need for union. Changing it to just static makes your test case pass.

Edit: I think PHPStan normalizes the type static|\Illuminate\Support\Collection to \Illuminate\Support\Collection because it's the parent class.

But I couldn't figure out in which cases can it return Support/Collection instead of Eloquent/Collection Do you have any example?

[Daanra]

Edit: I think PHPStan normalizes the type static|\Illuminate\Support\Collection to \Illuminate\Support\Collection because it's the parent class.

Thanks for pointing me in the right direction, I wasn't aware of this. This is kind of weird though. static|\Illuminate\Support\Collection is a perfectly valid type and is definitely not equivalent to just \Illuminate\Support\Collection. Anyhow, this is more a PHPStan problem.

The unique return type was indeed incorrect, so I fixed it here.