Test Proxy generation return type

test-proxy-generation-return-type.php

<?php

use Magento\Framework\App\Area;

require __DIR__ . '/app/bootstrap.php';

/**
 * Class Hello
 */
class Hello
{
    /**
     * @return string
     */
    public function sayHello(): string
    {
        return "Hello !!";
    }
}

/**
 * Class ProxyTestApp
 */
class ProxyTestApp extends \Magento\Framework\App\Http implements \Magento\Framework\AppInterface
{
    public function launch()
    {
        $this->_state->setAreaCode(Area::AREA_GLOBAL);
        $this->_objectManager->configure($this->_configLoader->load(Area::AREA_GLOBAL));

        /** @var Hello $helloProxy */
        $helloProxy = $this->_objectManager->get(\Hello::class . '\Proxy');

        $this->_response->setBody($helloProxy->sayHello());
        //the method must end with this line
        return $this->_response;
    }

    public function catchException(\Magento\Framework\App\Bootstrap $bootstrap, \Exception $exception)
    {
        return false;
    }
}

$bootstrap = \Magento\Framework\App\Bootstrap::create(BP, $_SERVER);

/** @var \Magento\Framework\App\Http $app */
$app = $bootstrap->createApplication('ProxyTestApp');
$bootstrap->run($app);