Only set return native type from null return type when declaring class is built in on __toString()

[samsonasik]

Start from PHPStan 2.1.14, in Rector, we got notice when downgrade code:

class ParentClassWithToStringMixedReturn
{
    public function __toString()
    {
        return 'a';
    }
}

class WithParentMixedReturn extends ParentClassWithToStringMixedReturn
{
    public function __toString()
    {
        return 'value';
    }
}

echo (new WithParentMixedReturn());

This add string return to WithParentMixedReturn::__toString() see https://3v4l.org/IrE2q#v7.4.33

The issue is when code consumed by user: https://3v4l.org/kdcEh#v7.4.33 it got error:

Fatal error: Declaration of Consumer::__toString() must be compatible with WithParentMixedReturn::__toString(): string in /in/kdcEh on line 21

On our rector-src code, I patch there with use our AstResolver to specify on __toString when no return and non-built in

• [PHPStan 2.1.14] Fix resolve __toString() parent non builtin method without return type rectorphp/rector-src#6879

to return MixedType

@TomasVotruba if this accepted, we may can rollback to original implementation 👍

[samsonasik]

@ondrejmirtes ready for review, not sure about the php 7.4 notice:

There was 1 failure:

1) PHPStan\Analyser\NodeScopeResolverTest::testFile with data set "tests/PHPStan/Analyser/nsrt/bug-2471.php" ('/home/runner/work/phpstan-src...71.php')
Failed assertions in /home/runner/work/phpstan-src/phpstan-src/tests/PHPStan/Analyser/nsrt/bug-2471.php:

Line 26:
Expected: array<string, null>
Actual:   array<null>

https://github.com/phpstan/phpstan-src/actions/runs/14802288573/job/41563600230?pr=3978#step:6:226

since other php versions green, could you give me hint to make it green? Thank you.

[ondrejmirtes]

1. How is __toString() different from other methods handled by this method?
2. Personally I'd like a test + revert of the commit that changed this (3854cbc) instead of this change.

[samsonasik]

1. we found by case, for current case is __toString() so don't know what other needs
2. yes, I think revert is better for this case, as native is native on overridden method.

[samsonasik]

#3979