False-positive `MixedArgument` (assignment in `if` clause)

[gharlan]

https://psalm.dev/r/fe8e19a6dc

In else branch $pos is always int.

[psalm-github-bot[bot]]

I found these snippets:

https://psalm.dev/r/fe8e19a6dc

<?php

function foo(?string $foo): ?string {
    if (null === $foo || false === $pos = strrpos($foo, '.')) {
        // do something
    } else {
        $foo = substr($foo, 0, $pos);
    }
    
    return $foo;
}

Psalm output (using commit ef3b018):

INFO: MixedArgument - 7:32 - Argument 3 of substr cannot be mixed, expecting int|null