Properties passed as arg 1 to array_pop are mutated, but checks for pure methods do not see the property as mutated

[DaveLiddament]

See example: https://psalm.dev/r/b0916c1ed2

I'd expect line 16 to be reported as an error. Something along the lines of:

ImpurePropertyAssignment - 16:9 - Cannot assign to a property from a mutation-free context

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/b0916c1ed2

<?php declare(strict_types = 1);

class Stack
{
	/** @var array<string> */
    private array $stack = [];

	public function push(string $item): void
	{
		$this->stack[] = $item;
	}

    /** @psalm-mutation-free */
    public function next(): string|null
	{
		return array_pop($this->stack);
	}
}

function takesString(string $string): void {var_dump($string);}


$stack = new Stack();
$stack->push("Jane");
if ($stack->next() !== null) {
  takesString($stack->next());	
}

Psalm output (using commit e212b06):

ERROR: ForbiddenCode - 20:45 - Unsafe var_dump

[weirdan]

Naive approach doesn't work