Skip bindings for assignments in @.

[BenPH]

For any assignment this checks that none of its ancestors is an @. call before marking a binding. I'm happy to hear any suggestions if there is a better approach.

Fixes julia-vscode/julia-vscode#2514

[pfitzseb]

I think this is fine. Bit concerned that iterating arbitrarily far up in the CST in too many places is gonna tank performance though...

[BenPH]

That was my concern too. There could be a limit where it stops. But maybe the better approach is to have some kind of flag once you enter an @. macro call that gets checked at assignments. I wasn't sure how to implement that without changing too much.

[pfitzseb]

So I think we can add a state field to the various States that can disable certain functionality for all children of the current node (since traverse is depth-first). I can push a proof of concept to your branch if you want.

[pfitzseb]

Man, working across forks is annoying...
Anyways, what do you think about BenPH#1?

[BenPH]

I like it. Very clean. That's a neat trick with the bit arithmetic for the flags.