function foo(string $s): void {
	$a = null;
	/* HAKANA_FIXME[RedundantTypeComparison] Type string is always string */
	if (rand(0, 1)) $a = $s is string ? 'a' : 'b';
	/* HAKANA_FIXME[RedundantTypeComparison] Type string is always string */
	$b = (mixed $a) ==> $s is string ? $a : null;
	$c = (mixed $a) ==> {
		/* HAKANA_FIXME[RedundantTypeComparison] Type string is always string */
		if ($s is string) {
			return $a;
		}
		return null;
	};
}