Weird error on unset of array

[jackbentley]

Bug report

I'm utilising the Symfony Normalizer in my project. I've only got PHPStan on level 2 but this error occurs when trying to unset a value returned in the serializer.

Cannot unset offset 'id' on array('bar' => 'b').

Code snippet that reproduces the problem

<?php declare(strict_types=1);

class HelloWorld
{
    /**
     * This method represents \Symfony\Component\Serializer\Normalizer\NormalizerInterface::normalize().
     *
     * @return array|string|int|float|bool|null
     */
    public function getArray()
    {
        return ['id' => 1];
    }

    public function test()
    {
        $data = $this->getArray();

        $data['foo'] = 'a';
        $data['bar'] = 'b';

        unset($data['id']);

        return $data;
    }
}

Expected output

No errors.

Examples

This shows the error:
https://phpstan.org/r/d3f05294-9abc-4f48-ad77-c71d371b4cfd

However, when removing either of lines 8/20/21 the error goes away...
https://phpstan.org/r/fba7b0b0-735f-4ba5-8fc4-b33a94dcff04
or... https://phpstan.org/r/4b79df96-40b4-4720-b270-ac98455f80b3

[ondrejmirtes]

This is happening because you're getting a union type array|string|int|float|bool|null but you're acting like you always have an array. Compare with: https://phpstan.org/r/f9633645-6866-48d6-9f7a-b4c4bbaeb4de

See: https://phpstan.org/writing-php-code/narrowing-types

I agree something should be done about this bug but you need to fix your code anyway :) Otherwise this issue would be reported on level 7: https://phpstan.org/r/f3e6a76b-5f55-4940-89fb-f7f0c4a2e4e7

[jackbentley]

Thanks for the response 😄Agreed, the code isn't the best and needs fixing regardless really.

What I find most odd about this bug is that it only shows after altering the array the second time: https://phpstan.org/r/4b79df96-40b4-4720-b270-ac98455f80b3

[ondrejmirtes]

This is what's happening (PHPStan internals): https://phpstan.org/r/e1bdb0e3-c668-418a-9827-37f855cd8302

[phpstan-bot]

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

@@ @@
-22: Cannot unset offset 'id' on array('bar' => 'b').
+22: Cannot unset offset 'id' on array{bar: 'b'}.

Full report

Line	Error
22	Cannot unset offset 'id' on array{bar: 'b'}.

[phpstan-bot]

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

@@ @@
 22: Cannot access offset 'foo' on array|bool|float|int|string.
-25: Cannot unset offset 'id' on array('bar' => 'b').
+25: Cannot unset offset 'id' on array{bar: 'b'}.

Full report

Line	Error
22	`Cannot access offset 'foo' on array
25	Cannot unset offset 'id' on array{bar: 'b'}.

[phpstan-bot]

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

@@ @@
-22: Cannot unset offset 'id' on array('bar' => 'b').
+22: Cannot unset offset 'id' on array{bar: 'b'}.

Full report

Line	Error
22	Cannot unset offset 'id' on array{bar: 'b'}.

[phpstan-bot]

@jackbentley After the latest push in 1.8.x, PHPStan now reports different result with your code snippet:

@@ @@
-22: Cannot unset offset 'id' on array('bar' => 'b').
+No errors

[phpstan-bot]

@ondrejmirtes After the latest push in 1.8.x, PHPStan now reports different result with your code snippet:

@@ @@
-22: Cannot access offset 'foo' on array|bool|float|int|string.
-25: Cannot unset offset 'id' on array('bar' => 'b').
+22: Cannot access offset 'foo' on array|bool|float|int|string.

Full report

Line	Error
22	`Cannot access offset 'foo' on array

[phpstan-bot]

@ondrejmirtes After the latest push in 1.8.x, PHPStan now reports different result with your code snippet:

@@ @@
-22: Cannot unset offset 'id' on array('bar' => 'b').
+No errors

[github-actions]

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