Optional Chaining (aka Existential Operator, Null Propagation)

[Claude Pache]

> Le 4 févr. 2016 à 21:03, Kevin Smith <zenparsing at gmail.com> a écrit :
> 
> (...)  The syntax still seems problematic, though, from an aesthetic point of view.
> 
> The `obj ?. prop` form looks natural and aligns well with how this feature appears in other languages.  The other forms are less natural:
> 
> obj?.[expr] 
> func?.(...args)
> new C?.(...args)
> 
> I'm not particularly convinced by any of the other syntactic variants we've seen.

Yeah, I fear that we couldn’t find a "good" syntax for those, given that  `obj?[expr]` and `func?(...args)` are most probably excluded  :-(

```js
o.x?[y]+z     // should be parsed as:  (o.x?[y]) + z
o.x?[y]+z:t   // should be parsed as:  o.x ? ([y] + z) : t
```

—Claude