Accessing undefined array key could result to null

[davidbrnovjak]

Bug report

When accessing annotated array it is possible to get null as a result when the key is undefined.
Currently no error is emitted and even checking if result is null is considered as an error (comparsion is always false).

(Sorry if duplicate, I really tried to search hard this time. This might be related #3126 )

Code snippet that reproduces the problem

https://phpstan.org/r/aedb5786-c0ba-4fc8-b311-f2a1c150f6c8

/** @var string[] */
$arr = ['a', 'b'];

$value = $arr[5];
if ($value === null) { // comparsion is always false emitted here
}

Expected output

Phpstan should treat accessing array by index as possible null.

[ondrejmirtes]

Hi, this isn't considered because you should check that the key exists using array_key_exists or isset. Accessing an undefined array key generates a warning, you should log notices and warnings in production and fix them so that your error logs are clean.

[github-actions]

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