PHPStan hangs on analysing small function

[phpfui]

Bug report

On PHPStan 0.12.33 under Windows 10, PHP 7.4.6.

PHPStan hangs on processing this file (chopped down from working code, this code does not make sense):

Code snippet that reproduces the problem

function fred($request)
	{
		$keys = '';
		foreach ($request as $index)
			{
			foreach ($index as $field)
				{
				if (isset($keys[$field]))
					{
					$keys[$field] = 0;
					}
				}
			}
	}

Expected output

PHPStan finishes, probably with some errors, but it never returns.

It is the first and only file processed. Level 1. If you change just about anything, it does not hang. This is the smallest snippet of code I could make hang. It was hanging on old production code, so pretty sure the code is valid PHP and works correctly with no errors or warnings reported.

[mergeable]

This bug report is missing a link to reproduction on phpstan.org.
It will most likely be closed after manual review.

[phpfui]

I am unable to see how to save a link to the demo / test page. When I copy and paste the above code into the page, I get this error:

An error occured. Please try again later.

[ondrejmirtes]

Can confirm this behaviour, will look into it.

[muglug]

Here's a properly-typed version that should pass:

<?php

/**
 * @param int[][] $a
 */
function replaceStringWithZero(array $a) : string {
    $keys = 'agfsdafsafdrew1231414';

    foreach ($a as $b) {
        foreach ($b as $c) {
            if (isset($keys[$c])) {
                $keys[$c] = "0";
            }
        }
    }

    return $keys;
}

[ondrejmirtes]

Fixed: phpstan/phpstan-src@6d81881

[phpfui]

Thank you!

[github-actions]

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