Return type for json_decode based on second parameter

[luxemate]

Summary of a problem or a feature request

json_decode has second parameter to determine if result is an array or \stdClass. It would be nice to catch cases when there's no assoc: true, and code is trying to access the result of json_decode as an array and vice versa.

Code snippet that reproduces the problem

No error for:

<?php declare(strict_types = 1);

$data = json_decode('{"foo": "bar"}');

$foo = $data['foo'];

https://phpstan.org/r/936624ae-ac3f-4f70-afad-e6480a19a6e6

Expected output

Cannot use object of type stdClass as array

https://3v4l.org/KCXIa

[ondrejmirtes]

Hi, this isn't practical because the return type of json_decode is marked as mixed, for good reasons. There's no guarantee that the string in the first argument is an object, you can do json_decode('1')., therefore assoc=true does not have any effect: https://3v4l.org/f1Xr0

[luxemate]

@ondrejmirtes Yea... I remembered of documentation line

Values true, false and null are returned as TRUE, FALSE and NULL respectively.

after creating the issue.

Return type ends up to be:
For assoc: false the return type is \stdClass|bool|null.
For assoc: true the return type is array|bool|null.

And it's not easy to determine which one will be there without actually running the code.

[ondrejmirtes]

That's too annoying, because it would complain when passing the result somewhere...

array|bool|null -> array (only arrays accepted, bool|null also present)

[luxemate]

I agree. :)