False positives on 2.1.39

[brendt]

Bug report

We noticed our builds breaking with phpstan:2.1.39 this morning: https://github.com/tempestphp/tempest-framework/actions/runs/21941333454/job/63367582331?pr=1960

The errors here are false positives, reverting back to 2.1.38 make them go away.

Code snippet that reproduces the problem

No response

Expected output

No errors

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[mergeable]

This bug report is missing a link to reproduction at phpstan.org/try.

It will most likely be closed after manual review.

[xHeaven]

This issue is related to #14036.
The issue only happens on Linux because it's case-sensitive, which is why we couldn't reproduce it with @brendt in macOS environments.

The culprit appears to be this commit, where the caching was changed from case-sensitive to case-insensitive.

On top of this, due to the nature of this regression, it's not possible to create a reproduction via phpstan.org/try.

A workaround for us is this:

parameters:
    scanDirectories:
        - packages

A possible fix that wouldn't mess up performance would be this:

/** @var array<lowercase-string, true> */
private array $knownClasses = [];

/** @var array<string, true> */
private array $unknownClasses = [];

public function hasClass(string $className): bool
{
    if (isset($this->knownClasses[strtolower($className)])) {
        return true;
    }

    if (isset($this->unknownClasses[$className])) {
        return false;
    }

    $result = $this->provider->hasClass($className);

    if ($result) {
        $this->knownClasses[strtolower($className)] = true;
    } else {
        $this->unknownClasses[$className] = true;
    }

    return $result;
}

[staabm]

excellent, thank you.

I had problems reproducing it on macOs, too.

but in the github action I can now reproduce phpstan/phpstan-src#4891