rector/config/set/phpspec40.php

<?php

declare (strict_types=1);
namespace RectorPrefix20210808;

use PHPStan\Type\ArrayType;
use PHPStan\Type\MixedType;
use Rector\TypeDeclaration\Rector\ClassMethod\AddReturnTypeDeclarationRector;
use Rector\TypeDeclaration\ValueObject\AddReturnTypeDeclaration;
use Symfony\Component\DependencyInjection\Loader\Configurator\ContainerConfigurator;
use Symplify\SymfonyPhpConfig\ValueObjectInliner;
return static function (\Symfony\Component\DependencyInjection\Loader\Configurator\ContainerConfigurator $containerConfigurator) : void {
    $services = $containerConfigurator->services();
    $arrayType = new \PHPStan\Type\ArrayType(new \PHPStan\Type\MixedType(), new \PHPStan\Type\MixedType());
    $services->set(\Rector\TypeDeclaration\Rector\ClassMethod\AddReturnTypeDeclarationRector::class)->call('configure', [[\Rector\TypeDeclaration\Rector\ClassMethod\AddReturnTypeDeclarationRector::METHOD_RETURN_TYPES => \Symplify\SymfonyPhpConfig\ValueObjectInliner::inline([new \Rector\TypeDeclaration\ValueObject\AddReturnTypeDeclaration('PhpSpec\\ObjectBehavior', 'getMatchers', $arrayType)])]]);
};