Rule source on GitHub

DowngradeReflectionMethodHasPrototypeRector

Downgrade ReflectionMethod::hasPrototype() by emulating it with getPrototype()

 class SomeClass
 {
     public function run(ReflectionMethod $reflectionMethod): bool
     {
-        return $reflectionMethod->hasPrototype();
+        return (function (\ReflectionMethod $reflectionMethod2): bool {
+            try {
+                $reflectionMethod2->getPrototype();
+                return true;
+            } catch (\ReflectionException) {
+                return false;
+            }
+        })($reflectionMethod);
     }
 }

Configure your rector.php:

<?php

use Rector\Config\RectorConfig;
use Rector\DowngradePhp82\Rector\MethodCall\DowngradeReflectionMethodHasPrototypeRector;

return RectorConfig::configure()
    ->withRules([
        DowngradeReflectionMethodHasPrototypeRector::class,
    ]);