https://en.wikipedia.org/wiki/Attribute_grammar

This doesn't need to be a free-form attribute grammar, but there needs to be some kind of information decoration such that the parse can synthesize some AST. Having a bool parse(...) function isn't very useful; we want to be able to extract the parse tree information.

When designing this, keep in mind that it is desirable to be able to support free-form attributes on the grammar, because added flexibility in that way is something very powerful with Bison that may be worth replicating here. For the first pass, there's no need to stress over it.