public function main()
    {
        if ($this->realThing === null) {
            // plain impossible to get here, maybeConfigure should
            // have thrown an exception.
            throw new BuildException("Should not be executing UnknownElement::main() -- task/type: {$this->elementName}");
        }

        if ($this->realThing instanceof Task) {
            $this->realThing->main();
        }
    }