add syncheck:import-or-export-prefix-ranges

[rfindler]

Not sure if this is immediately (or ever?) useful, but it was easy to make and it seems like it fits here, so I made it.

Related to racket/racket#4649

[greghendershott]

It seems potentially useful for other folks, but not quite what I need for pdb. I plan to submit a PR for that, but TL;DR: pdb needs to know about all imports and exports; the new stx prop is just an additional detail about those.

• pdb needs to know about each fully expanded #%provide clause. One way to look at this is, something like add-definition-target, but for exports (i.e. "add-export-target"). When it's a rename clause, it needs to know both the local-id and export-id. Given those, it can directly check for the property on the latter.

• pdb needs to know about each fully expanded #%require clause, too. Here both as a source for completion candidates, and also when it's a rename clause, both the local-id and imported-id. Given the local-id it, can look for the stx prop.

The analyze-more.rkt file shows roughly what I would propose to add in check-syntax traversals.rkt (if not necessarily the exact new syncheck method signature and style).

But again I plan to prepare a PR for this, for you to review.

[rfindler]

Oh! Okay! Thanks, Greg.

[greghendershott]

If I should make a fresh issue for this, please let me know, but:

A potential to-do would be for check-syntax to add arrows for prefixes described by this new syntax property.

In other words, generalize how it handles the single prefix case, indicated by the low-level prefix clause in #%require, to one or more prefixes.

So for things like (prefix-in A: (prefix-in B: mod)) it would do more add-arrow-*s and more add-prefixed-require-references, for both A: and B:, whereas today it does none.

[The only reason I need the syntax property, for imports^1, is to draw more arrows that check-syntax currently doesn't draw for me in the first place.^2]

Is that something you'd be willing to do? (I took an initial look in traversals.rkt. I feel like you'd be able to do this more quickly -- and to your greater satisfaction -- than me attempting it. And I have plenty else on my plate right now. But if you don't have time I can attempt this later and do a PR.)

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^1: For prefixed exports it's a different, bigger story, involving potentially both this property and sub-range-binders (e.g. (prefix-out foo- (struct-out bar))). But I think that's much lower-priority; I have it working in pdb, and the value to end users visually in e.g. DrRacket seems much less.

^2: There are some other reasons I draw more arrows, but the prefix arrows are one subset.

[rfindler]

I can give this a try, yes and thanks for pointing out the lack!