False positive: MethodSignatureMustProvideReturnType in __toString()

[derrabus]

The MethodSignatureMustProvideReturnType check tells me if I need to add a native return type to a function in order to avoid a deprecation notice on PHP 8.1+.

However, it is also triggered on __toString() although PHP does not trigger a deprecation here.

https://psalm.dev/r/687115a153
https://3v4l.org/uHsSj

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/687115a153

<?php

class MyClass
{
    /** @return string */
    public function __toString()
    {
        return 'foo';
    }
}

Psalm output (using commit 028ac7f):

ERROR: MethodSignatureMustProvideReturnType - 6:21 - Method MyClass::__toString must have a return type signature!

[orklah]

Thanks for the feedback!

Unfortunately, this issue only exists on the website(and our master branch) for now but it was disabled on 4.x and soon will be disabled on master.

It was causing a lot of false positives for plugin users because Psalm wrongly considers plugin stubs as part of php core. We won't fix your bug for now because we don't know when this issue will be enabled again.

[derrabus]

Sorry, I should've mentioned that I found this issue while testing Psalm 5. Psalm 4 is not affected as far as I can tell.

[derrabus]

Thank you for your answer!

[orklah]

Thank you for testing Psalm 5 :) It's very helpful to get feedback!

[derrabus]

The error is still present in 5.0.0-rc1. Shall we reopen the issue?

[orklah]

Most definitely!

[orklah]

@danog do you know what happened here?

We merged your PR for this issue here: #7363
But then we had to revert it here: #7539 because stubs are wrongly qualified as not "user_defined". This was making Psalm enforce wrong return types coming from stubs

But it still end up in master? Do you remember us re-adding it later? Or maybe a mishandling on my part?