https://www.php.net/manual/en/function.rewinddir.php

PHP documentation for rewinddir() has a bug: return type is not void, but is null or false (see https://www.php.net/manual/en/function.rewinddir.php#refsect1-function.rewinddir-returnvalues).

Example:

$handle = opendir(__DIR__);
var_dump(rewinddir($handle)); // NULL
closedir($handle);
var_dump(rewinddir($handle)); // false with an E_WARNING triggered

It seems that phpstan follow the documentation, because the example above will trigger this error with phpstan:

Result of function rewinddir (void) is used.

Tested on PHP 7.1.0, 7.2.0, 7.3.0 and 7.4.0.