Deep nil coalescing `??`

[antonmedv]

Right now, in order to use ?? user have to use ?. instead of . in nested structures.

events[0]?.labels?.value ?? 'defaul'

My idea is to make left hand side of ?? optional by default. So in case user written:

events[0].labels.value ?? 'defaul'

All member accesses to label/value/events will be optional. As well as array element access.

I really like this idea and think it makes much sense.

[antonmedv]

Also implement opcode to do chained optional fetch

[ckganesan]

@antonmedv : I have addressed these issues in the pull request. Could you please review this PR #583

[antonmedv]

Cool! Will take a look!