array_filter w/ empty callback may return empty array

[b1rdex]

The playground is broken, so the raw code:

$someVar = 'now';
$uppedDate = new DateTime($someVar);
$diff = $uppedDate->diff(new DateTime());

$mdiff = (int)$diff->format('%m');
$ddiff = (int)$diff->format('%d');
$content = array_filter([$mdiff, $ddiff]);

// if condition is always true
if ($content) {
    die();
}

// the error is gone
if (\count($content) > 0) {
	die();
}

$content = array_filter([$mdiff, $ddiff], fn(): bool => false);
// the error is gone
if ($content) {
	die();
}

1. array_filter w/ empty callback might return an empty array
2. why count()ing the result removes the error?

[ondrejmirtes]

Please reproduce it now.

[b1rdex]

The original code: https://phpstan.org/r/af2a9cfe-e058-47b5-a63f-b6d0eeb90709
Surprisingly, count() doesn't fix it.

Here is the more complicated (but closer to the original code w/ the issue) example: https://phpstan.org/r/4b5a185e-ec7a-4b38-a9ce-1a6e8be65a40
count() fixes it somehow

[ondrejmirtes]

Fixed: phpstan/phpstan-src@d22abbe

[github-actions]

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