Bug report

I noticed that the following code produces four warnings:

<?php

use function PHPStan\Testing\assertType;

interface ResourceInterface {}

class Person implements ResourceInterface 
{
	public function getName(): string { return 'Name'; }
}

class Account implements ResourceInterface
{
	public function getMail(): string  { return 'Mail'; }
}

function foo(?ResourceInterface $object = null): void
{
	switch ($object::class) {
		case Person::class:
			assertType(Person::class, $object);
			echo $object->getName();
			break;
		case Account::class:
			assertType(Account::class, $object);
			echo $object->getMail();
			break;
	}
}

Code snippet that reproduces the problem

https://phpstan.org/r/f9c2c069-07b2-46a3-b83c-837205e6581f

Expected output

The errors surprised me, as the type is actually checked and, hence, the code reported by PhpStan will not produce any errors during runtime. The feature of checking types by switch was covered in #745, #4896.

I found, however, that the code above seems to be related to $object being nullable. If you change the method signature from ?ResourceInterface $object = null to ResourceInterface $object, the errors are suddenly gone!

Next, I discovered that accessing ::class on null actually throws an error in PHP 8.4.7 (and probably all PHP 8 versions):

$ php -r "\$foo = null; var_dump(\$foo::class);"
PHP Fatal error:  Uncaught TypeError: Cannot use "::class" on null in Command line code:1
Stack trace:
#0 {main}
  thrown in Command line code on line 1

So PhpStan is actually right in reporting something, though I think the reported errors are incorect. In my opinion, PhpStan should complain about accessing ::class on nullable types.

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