PHPStan assues classes do not exist when conditionally defined classes are accessed inside a class_exists() block

[driehle]

Bug report

There can be a scenario, where a class may either exist or not exist, e.g. because of an optional dependency or because of supporting different versions of an upstream library. In such a scenario it is typical to check with class_exists if the corresponding class exists or not.

If the class does not exist, it seems like PHPStan inflects that such class cannot be a class-string. This leads to a type error.

Code snippet that reproduces the problem

Consider the following code, a snippet from DoctrineORMModule:

    /**
     * @return list<array{string, class-string}>
     */
    public function dataProviderForTestValidCommands(): array
    {
        $data = [
            // left out some commands here for simplicity ...
            // [...]
            [
                'migrations:execute',
                ExecuteCommand::class,
            ],
        ];

        // this is only available with DBAL 2.x
        if (class_exists(ImportCommand::class)) {
            $data[] = [
                'dbal:import',
                ImportCommand::class,
            ];
        }

        return $data;
    }

There should be no issue, as the result always holds the type list<array{string, class-string}>. However, PHPStan produces the following error on level 3:

 ------ -------------------------------------------------------------------------------------------------------------
  Line   tests/CliConfiguratorTest.php
 ------ -------------------------------------------------------------------------------------------------------------
  237    Method DoctrineORMModuleTest\Listener\CliConfiguratorTest::dataProviderForTestValidCommands() should return
         array<int, array{string, class-string}> but returns array{0: array{'dbal:run-sql',
         'Doctrine\\DBAL\\Tools\\Console\\Command\\RunSqlCommand'}, 1: array{'dbal:reserved-words',
         'Doctrine\\DBAL\\Tools\\Console\\Command\\ReservedWordsCommand'}, 2: array{'orm:clear-cache…',
         'Doctrine\\ORM\\Tools\\Console\\Command\\ClearCache\\QueryCommand'}, 3: array{'orm:clear-cache…',
         'Doctrine\\ORM\\Tools\\Console\\Command\\ClearCache\\ResultCommand'}, 4: array{'orm:generate-proxies',
         'Doctrine\\ORM\\Tools\\Console\\Command\\GenerateProxiesCommand'}, 5: array{'orm:ensure…',
         'Doctrine\\ORM\\Tools\\Console\\Command\\EnsureProductionSettingsCommand'}, 6: array{'orm:info',
         'Doctrine\\ORM\\Tools\\Console\\Command\\InfoCommand'}, 7: array{'orm:schema-tool…',
         'Doctrine\\ORM\\Tools\\Console\\Command\\SchemaTool\\CreateCommand'}, ...}.
 ------ -------------------------------------------------------------------------------------------------------------

Expected output

I would expect PHPStan not to raise any issues here.

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[mergeable]

This bug report is missing a link to reproduction on phpstan.org.

It will most likely be closed after manual review.

[driehle]

See https://phpstan.org/r/7686888a-462c-43d7-a496-47e1242a14a4 for a snippet.

[ondrejmirtes]

Fixed: phpstan/phpstan-src@da34d3f

[driehle]

Wow, that was ridiculously fast! 🚀 Thanks!

[github-actions]

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