Nullish coalescing operator ??

[jorendorff]

Stage 3 proposal
Spec repo: https://github.com/tc39/proposal-nullish-coalescing

(Related to #146 optional chaining, but an independent proposal.) We just implemented ?? in SpiderMonkey. It's a short-circuiting binary operator, more like || than anything else, but calling it a LogicalExpression is a stretch.

[RReverser]

Hmm. Adding it as a LogicalExpression operator could be nice / easy implementation-wise, but I see why semantically it doesn't make much sense.

@hzoo @loganfsmyth @danez What do you think?

[michaelficarra]

LogicalExpression seems fine to me.

[codehag]

In the proposed specification LogicalExpression is updated to ShortCircuitExpression - does it make sense to update it here as well?

[michaelficarra]

@codehag The organisation and names of the grammar productions in the spec should not affect our designs here. Also, estree cannot make backward incompatible changes such as the one you suggest.

[codehag]

ok, thanks for the context

[jorendorff]

Thanks for the replies here. We're implementing this in SpiderMonkey with "LogicalExpression" in https://phabricator.services.mozilla.com/D52690.

[fabiosantoscode]

👍 Terser will follow suit.

[JLHwung]

This issue is fixed by #211.

[RReverser]

@JLHwung Right, thanks.