ClassStatementsGatherer gathers all 2-element arrays into methodCalls, triggering class reflection in UnusedPrivateMethodRule #15494

Bug report

In ClassStatementsGatherer, any 2-element array expression is unconditionally collected into $this->methodCalls as a candidate callable:

if ($itemCount === 2) {
    $this->methodCalls[] = $node;
}

When the enclosing class declares at least one private method, UnusedPrivateMethodRule iterates through all collected methodCalls and calls $arrayType->isCallable() on each one.

For 2-element data arrays whose first item is a class name (e.g. [BigContainer::class, 'packstation'] or string pairs), ConstantArrayType::isCallable() triggers reflection on that target class. However, private methods of the current class can only be called on $this, self, static, or the current class name itself. Collecting unrelated 2-element data arrays causes unnecessary class reflection.

I opened phpstan/phpstan-src#6759 with a proposed fix. Submitting this issue with the reproducer as requested by @staabm.

Code snippet that reproduces the problem

<?php

namespace App;

class BigContainer
{
}

class Service
{
    private function unusedMethod(): void
    {
    }

    public function process(string $item): bool
    {
        $modes = [BigContainer::class, 'packstation'];
        return in_array($item, $modes, true);
    }
}

Expected output

Two-element arrays whose first item cannot refer to the current class should not be gathered into ClassStatementsGatherer::$methodCalls, avoiding unnecessary class reflection during unused private method analysis.