core-bundle/src/HttpKernel/ModelArgumentResolver.php
private function getArgumentName(Request $request, ArgumentMetadata $argument): ?string
    {
        if ($request->attributes->has($argument->getName())) {
            return $argument->getName();
        }

        $className = lcfirst($this->stripNamespace($argument->getType()));

        if ($request->attributes->has($className)) {
            return $className;
        }

        return null;
    }
private function getArgumentName(Request $request, ArgumentMetadata $argument): ?string
    {
        if ($request->attributes->has($argument->getName())) {
            return $argument->getName();
        }

        $className = lcfirst($this->stripNamespace($argument->getType()));

        if ($request->attributes->has($className)) {
            return $className;
        }

        return null;
    }
Returns the argument name from the model class.