Good APIs for scope analyzers

Question

I'm working on some code generation tools, and a lot of complexity comes from doing scope analysis. I frequently find myself wanting to know things like

1. What are the free variables of a function or block?
2. Where is this symbol declared?
3. What does this declaration mask?
4. Does this usage of a symbol potentially occur before initialization?
5. Does this variable potentially escape?

and I think it's time to rethink my scoping kludge.

I can do all this analysis but am trying to figure out a way to structure APIs so that it's easy to use, and ideally, possible to do enough of this work lazily.

What tools like this are people familiar with, and what did they do right and wrong in their APIs?