Support tracing across reference boundaries

[shyndman]

Hi there,

I noticed that trace parsers are unable to trace the "children" of Reference parsers, which would be handy.

I got around this without too much trouble (little code change, and introduced the trace in the referenced function), but it would be really nice to see a cohesive trace through the entirety of the input, with proper indentation and all that.

Anyway, thanks! This library has proven useful for a tiny DSL I'm writing.

[shyndman]

Ah, I see now why this is a little tricky. Hmmm

[renggli]

Reference boundaries disappear when the parser is built, I don't see how they would affect the trace if it is applied just before parsing? Can you provide an example?

[shyndman]

So right now I'm applying the trace inside my GrammarDefinition...should I be wrapping my GrammarParser instance in the trace instead?

[shyndman]

Yes. That worked perfectly. Thank you.

[renggli]

Yeah, it does not work inside the GrammarDefinition, it only works after the parser is built. Similar issue as #39.