private function make(string $class)
    {
        if (! array_key_exists($class, $this->instances)) {

            try {

                return $this->instances[$class] = ($this->factory)($class)->value($this);

            }

            catch (ResolvingExceptionInterface $e) {

                throw new ReflectionContainerException($class, $e);

            }

        }

        return $this->instances[$class];
    }