SimpleXMLElement + null safe operator results in errors

[PHLAK]

Bug report

When using the null safe operator with SimpleXMLElement phpstan reports an error. More specifically, phpstan doesn't seem to understand that the properties of a SimpleXMLElement object can possibly return null.

Using nullsafe property access on non-nullable type SimpleXMLElement. Use -> instead.

Code snippet that reproduces the problem

https://phpstan.org/r/68f49c78-6d49-4e4c-96f0-83562eff662e

Here's some additional code illustrating the way properties on the SimpleXMLElement object work.

>>> $foo = new SimpleXMLElement('<foo>asdf</foo>')
=> SimpleXMLElement {#5830
     +"0": "asdf",
   }
>>> $foo
=> SimpleXMLElement {#5830
     +"0": "asdf",
   }
>>> $foo->bar
=> SimpleXMLElement {#5839}
>>> $foo->bar->baz
=> null
>>> $foo->bar->baz->qux
<warning>PHP Warning:  Attempt to read property "qux" on null in eval()'d code on line 1</warning>
=> null

This is a bit odd because $foo->bar (a non-existent element in the XML) returns an empty SimpleXMLElement. Perhaps I'm missunderstanding the way the SimpleXMLElement object works.

Expected output

No errors

[phpstan-bot]

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

@@ @@
-5: Expression "$xml->foo?->bar?->baz" on a separate line does not do anything.
-5: Using nullsafe property access on non-nullable type SimpleXMLElement. Use -> instead.
-5: Using nullsafe property access on non-nullable type SimpleXMLElement. Use -> instead.
+5: Expression "$xml->foo?->bar?->baz" on a separate line does not do anything.

Full report

Line	Error
5	Expression "$xml->foo?->bar?->baz" on a separate line does not do anything.

[ondrejmirtes]

Fixed by: phpstan/phpstan-src#76

[PHLAK]

Awesome, thanks @ondrejmirtes!

[github-actions]

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