Adding the ?. null verification

[Etienne via Digitalmars-d]

> In this case auto completion could work flawless because of
>
> alias this t;
>
> At least for cases where even a frontend based tool has a hard time, we
> could introduce a ddoc section for this, if there really is a need.
>
> /**
>   * Dispatch method call.
>   * Completion: LIKE t
>   */
> auto opDispatch(string field)() { ... }
>
> If phobos does this consistently the tools will recognize this.
>

Nice, that's a great trick (recognizing alias this t). Mono-D doesn't 
have that yet, I'll get the word accross