Narrow the subject of a match(...) clause based on the narrowing of its result #14772

function test_if(mixed $x) {
	if ($x === 'aa')
		$class = 'some_class';
	elseif ($x === 'bb' || $x === 'cc')
		$class = 'another_class';
	else 
		$class = null;
	if ($class === null)
		 return;
	\PHPStan\dumpType($x); // 'aa'|'bb'|'cc'
};

function test_match(mixed $x) {
	$class = match ($x) {
		'aa' => 'some_class',
		'bb', 'cc' => 'another_class',
		default => null,		
	};
	if ($class === null)
		 return;
	\PHPStan\dumpType($x); // expected: 'aa'|'bb'|'cc'; actual: mixed
};