foreach already checked for zero length should not give $i might not be defined

[asgrim]

Summary of a problem or a feature request

When performing a foreach on an array, you can use the dangling reference of the loop ($things as $thing, you can use $thing still after the loop), but of course if the count of the array is zero, then $thing is rightly pointed out to be possibly not defined (Variable $thing might not be defined.). However, if we check the count($things) is non-zero before the iteration, phpstan should notice this and be satisfied that $thing would always be set.

Code snippet that reproduces the problem

See results: https://phpstan.org/r/48ec08fa293fa3ac9857d2c975188a13

<?php declare(strict_types = 1);

class Thing { public function foo() : void {} }

/** @var Thing[] $things */
$things = [new Thing(), new Thing()];

// This count check should tell phpstan that $thing exists down below
if (count($things) === 0) {
	// it's return from a method in our case, but die for example sake
	die();
}

foreach ($things as $thing) {
}

/** @var Thing $thing */
$thing->foo();

Actual output

 ------ --------------------------------------- 
  Line   analyzed.php                           
 ------ --------------------------------------- 
  18     Variable $thing might not be defined.  
 ------ --------------------------------------- 

Expected output

I expect no errors, the detected issue is a false positive.

[ondrejmirtes]

Yeah, unfortunately PHPStan doesn't track non-empty arrays yet. See also #1073.

[asgrim]

Aye I guess this is a duplicate, but the @var annotation doesn't seem to work in this case either :/

[ondrejmirtes]

I usually use this pattern: https://phpstan.org/r/f5ea92315b90dfbe8224c0deeed49a78

[adaamz]

Or check it after loop
https://phpstan.org/r/c5838a9a32825418d2c3d38e082614f3

[asgrim]

Thanks folks! I'm happy for this to be a duplicate of #1073 then (assuming they would be solved using the same approach). Meanwhile, workarounds work 👍

[ondrejmirtes]

Solved with 21309e2 (https://phpstan.org/r/8908dae7fe0a8497a8bd4260a4875077)