False positive of RemoveUselessVarTagRector

[dragosprotung]

Bug Report

Subject	Details
Rector version	last dev-main
Installed as	composer dependency

Minimal PHP Code Causing Issue

See https://getrector.com/demo/c779dd90-39ba-4cf1-8222-984a30d19816

<?php

interface Properties{}

/**
 * @template TProperties of Properties|null
 */
final class DemoFile
{
    /** @var TProperties */
    private Properties|null $properties;
}

Responsible rules

• RemoveUselessVarTagRector

Expected Behavior

Tag should not be removed

[samsonasik]

That's expected TProperties is defined as Properties|null, while native property tyep is Properties|null itself, so they are equal, so dead code is expected :)

even child implementor, using @template tag will mark as

Property DemoFile<TPropertyImpl of PropertiesImpl|null>::$properties (TPropertyImpl of PropertiesImpl|null) does not accept PropertiesImpl.

see:

https://phpstan.org/r/abf330cf-4372-49ac-ba92-51ffa77d0c3a

so possibly a phpstan bug on invalid detecting it :)

I suggest to change to just direct property definition, if child is used, see

https://phpstan.org/r/9414d887-ce5c-45c2-9985-b930517127cc

[dragosprotung]

@samsonasik null must be part of the template. This is because some implementations might always return null (they do not have properties).

Here is another example https://getrector.com/demo/00f806a6-3347-4011-aa9d-6ac589f56d21

[samsonasik]

You define TProperties of Properties|null, while property has native type already protected Properties|null $properties;, they are same.

[dragosprotung]

From a native perspective, you are right, they are the same.

But it's not about native types. In the case of a Printer the value will always be null and in the case of a Monitor the value will always be MonitorProperties.

Does Rector only look at the types only from a native perspective ?

[samsonasik]

You can use direct child implementor of native type as docblock if you don't want it to be removed, see https://getrector.com/demo/59fb3ce1-5118-44e2-a52f-2b3bdcaf66e1

[dragosprotung]

I need to keep the property in the base abstract class.

I've made the 2 versions for PHPStan:
https://phpstan.org/r/1ab4f06b-5184-46c3-bbd8-c30c6f418027 (with the @var tag)
https://phpstan.org/r/fff02c41-586a-42c6-84f1-66a5696953cf (without the @var tag)

I do not consider this a PHPStan bug.

I also made it in Psalm:
https://psalm.dev/r/00ee6fbeb9 (with the @var tag)
https://psalm.dev/r/447851edd4 (without the @var tag)

[samsonasik]

Ok, reopen then.