Problem assignin variable inside method is_null

[sdecandelario]

Bug report

When assign a variable inside a is_null function and then use this variable phpstan seems not to detect and considere that the variable can be null

Code snippet that reproduces the problem

<?php declare(strict_types = 1);

class HelloWorld
{
	public function sayHello(): ?string
	{
		return 'Hello';
	}
	
	public function test(): string{
		if(!is_null($hello = $this->sayHello())){
			return $hello;	
		}
		
		return 'No hello';
	}
}

https://phpstan.org/r/33610217-6278-4a1c-b2cc-dd9f9f837fcd

Expected output

No errors

[mergeable]

This bug report is missing a link to reproduction on phpstan.org.
It will most likely be closed after manual review.

[ondrejmirtes]

Yes, this is a bug, but you can easily go around it :) https://phpstan.org/r/917106e6-839c-43a0-aeff-a0c9153af49f

[b1rdex]

Alternatively, you could use null !== instead of !is_null: https://phpstan.org/r/a60c6dfc-901e-404d-a2f9-8c9dd5dcc30f. It fixes logic somehow.

[guilliamxavier]

Related to (maybe duplicate of) #2413

[phpstan-bot]

@sdecandelario After the latest commit in dev-master, PHPStan now reports different result with your code snippet:

@@ @@
-12: Method HelloWorld::test() should return string but returns string|null.
+No errors

[ondrejmirtes]

Fixed: phpstan/phpstan-src@b2bf703

[github-actions]

This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.