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Run Rector on your code to see what it can do for you:

 }
 
 (new SkipCallableParamAssignFluentMultiParams())
-    ->withTransform(fn (string $datum): string => trim($datum))
+    ->withTransform(trim(...))
     ->run('  some data  ');

PHP snippet to change

<?php

class SkipCallableParamAssignFluentMultiParams
{
    private $transform;

    /**
     * @param callable(mixed $datum, int|string|null $key): mixed $callable
     */
    public function withTransform(callable $callable)
    {
        $this->transform = $callable;
        return $this;
    }

    public function run($value, $optionalData = [])
    {
        var_dump(($this->transform)($value, $optionalData));
    }
}

(new SkipCallableParamAssignFluentMultiParams())
    ->withTransform(fn (string $datum): string => trim($datum))
    ->run('  some data  ');

Applied Rules:

FunctionLikeToFirstClassCallableRector

Not a change you expect?

Create an issue on GitHub
...or to speed up fix – add a test fixture

Config rector.php

<?php

use Rector\Config\RectorConfig;
use Rector\ValueObject\PhpVersion;

return RectorConfig::configure()
    ->withRules([
        \Rector\CodingStyle\Rector\FunctionLike\FunctionLikeToFirstClassCallableRector::class
    ])
    // demonstrate specific PHP version
    ->withPhpVersion(PhpVersion::PHP_84);

Rector version: b855ff - released at 2026-01-22 19:37