Parse code by source order.

[reitermarkus]

Extracted from #2369.

In order to somewhat support #undef, code needs to be parsed in the correct order. Previously, all macros were parsed before all variables, making it impossible to reason about whether a variable was declared before or after a macro with the same name.

[bors-servo]

☔ The latest upstream changes (presumably bfc5b7f) made this pull request unmergeable. Please resolve the merge conflicts.

[pvdrz]

If I understood correctly, the only case where this returns None is if neither the file is included in the other. Given that this is only called inside visit_sorted wouldn't it be clearer to just return cmp::Ordering::Equal in that case?

[pvdrz]

I just did a review and added a few comments, most of them are just about documentation.

Could you also please document these changes in the changelog. Mainly the fact that the order of the bindings has changed and that the __bindgen_ty_\d+ types might change name because of this?

Also I have a last question: The evaluation of define directives is not affected by this new ordering yet, right?

[reitermarkus]

The evaluation of define directives is not affected by this new ordering yet, right?

No, this is simply extracting this logic from #2369 for easier review.

[emilio]

@reitermarkus fyi, this broke Firefox (still working on a more reduced test-case). I'm a bit confused about this change tho. You completely ignore the CXChildVisit_{Break,Continue,Recurse} return value of the visitor? I'm surprised this didn't break more stuff.

[emilio]

I guess none of the callers cared about the different CXChildVisit but at least the API should be simplified to reflect the fact that the return value is ignored...

[pvdrz]

Hmmm... this is unfortunate. I'll try to review all the issues/PRs now.