False Positive with array declaration & array_merge

[mikaelBrosset]

phpstan with array_merge throws an error while declaring a new array;

$out[$k] = [];
$out[$k] = array_merge($out[$k], ['foo' => 'bar']);

// This comes in a foreach loop. Thus this might be the reason why.

This throws

Parameter #1 $arr1 of function array_merge expects array, array|string given.

But this should not show 'array|string' if I am correct !

Here is the link to the test : https://phpstan.org/r/ec3f94a5a68d29d017491a320190ca99

Thank you

Good day

[ondrejmirtes]

Please follow the instructions and add a link to phpstan.org reproduction.

[mikaelBrosset]

Link added for the test. Thank you very much.

[ondrejmirtes]

The $out[$k] is still array|string because the original array is (array|string)[]. We don't track the $out[$k] because it's hard - $k might have changed meanwhile.

[mikaelBrosset]

All right, thank you very much for the quick answer :)

[ondrejmirtes]

Please don’t close it, it’s still a valid bug waiting for a solution 😊

[dereuromark]

I have a different false positive here:

// Returns array as documented with keys that each contain an assoc array
$modules = static::releaseTypedModuleList($releaseGroup);

return $modules['major'] + $modules['minor'] + $modules['patch'];

PHPStan wrongly thinks too much here:

Method App\Model\Entity\ReleaseGroup::moduleList() should return array but returns (float|int).

Those are nested arrays, and the + operation on the assoc arrays are valid.

Manually applying casting seems to workaround it for now:

return (array)$modules['major'] + (array)$modules['minor'] + (array)$modules['patch'];

[ondrejmirtes]

@dereuromark You should check what PHPStan thinks that $modules['major'], $modules['minor'], $modules['patch'] are, by comparing them to some non-sense value like === 1. You can take advantage of the array shapes (https://phpstan.org/writing-php-code/phpdoc-types#array-shapes) to tell PHPStan precisely what it needs to think about those types.

[dereuromark]

I argue from the other direction
If the typehint and docblock states cleary just "array", then phpstan must NOT assume it to be more precise than "mixed[]"
Right now it does that, and that is invalid IMO.
Making it array-shaped can sure help, but the root cause here is phpstan overstepping the inspection of such a mixed case.

To be clear: + operator is not only for int/float, but also valid for array merge op.
If PHPStan cannot be 100% sure about it being the first, it should not report any issue.

[ondrejmirtes]

PHPStan knows that mixed + mixed can only ever be array|float|int so it uses that information.

Why it thinks in your case that it's just float|int - I don't know that, I'd need phpstan.org reproduction.

[dereuromark]

https://phpstan.org/r/7d71e14b-2165-4dd2-b25f-89228a4dfe8d shows it
We use it on level 5, so the other 2 errors about the shapes are not present anyway.

[ondrejmirtes]

Yeah, so this is a separate bug. It shows that (array|float|int) + mixed is (float|int) which is wrong.

[ondrejmirtes]

#3759

[ondrejmirtes]

This one is fixed already.

[github-actions]

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