Handle backtracking via transactional memory-ish constructs?

[stevefan1999-personal]

I was thinking about adding a set of API for "commit" and "rollback" for the symbol table: it will have a set of "snapshots" and when we kick back our parser to a certain point,. "rollback" action occurs reverting the symbol table to a previously state.

That way, we can properly backtrack without having ghost variables in the temporary symbol table. I'm not certain what this is called but I think there are people implemented things like this before, but the closest thing I can think of is transactional memory.

[kevinmehall]

This sounds like the state feature in Pegasus (C#). There's some discussion of that on #223.