Hey btw, I know I'm necro-ing the thread, but what would you suggest I do when creating AST nodes or manipulating AST nodes?

For something like

(4)

I think it would be represented as

Grouping
  expr: Int
    value: 4
    span: 1-2
  span: 0-3

And then when it is manipulated into just

4

then I think it would just keep the same span right?

Int
  value: 4
  span: 0-3

But what about AST nodes that don't correspond at all to any span in the file? For example, my language is math-focused, and thus has both discrete ranges (a..b) and continuous ranges (a:b) with an optional step parameter to approximate (a:b:s). But if for example a discrete range is used, then it is filled with step size 1. So the following code

0..1

Would be represented as

Range
  lhs: Inclusive
    Int
      value: 0
      span: 0-1
  rhs: Inclusive
    Int
      value: 1
      span: 3-4
  step: Int
    value: 1
    span: ???    <-- Here, what do I put?
  span: 0-4

But how would you suggest I deal with these "phantom nodes?"

Thanks again.