False positive with isset on nullable object's array property key

[ghost]

Summary of a problem or a feature request

Checking a nullable object's array property key with isset() yields the following error:

Cannot access property $arrayProperty on Foo|null

Code snippet that reproduces the problem

isset($nullableObject->arrayProperty['key'])

https://phpstan.org/r/7ec5332d-70c0-4307-aa4e-b28b69d712d4

Expected output

No errors.

If $nullableObject is NULL, isset() returns FALSE without any errors.

Changing the condition to isset($nullableObject) && isset($nullableObject->arrayProperty['key']) works, but it's a pointless extra check I'd rather avoid 🙂

[ondrejmirtes]

This is a feature. With isset($nullableObject->arrayProperty['key']), you're expressing that you're looking for whether the key exists there or not. See #1261.

So the code isset($nullableObject) && isset($nullableObject->arrayProperty['key']) is actually what you should use IMHO to express the right intent.

[ghost]

I understand. Should isset($nullableObject, $nullableObject->arrayProperty['key']) work then? It fails with the same error.

https://phpstan.org/r/436fbd52-13ed-4a63-a62c-0e387ad48a34

[ondrejmirtes]

Yeah, probably.

[ondrejmirtes]

Fixed by: phpstan/phpstan-src#345

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