Require tidying breaks on nested import of require transformer

[jackfirth]

As discussed here, this code:

(require "my-transformer.rkt"
         (my-transformer-in))

Is currently refactored by Resyntax into this:

(require (my-transformer-in)
         "my-transformer.rkt")

Assuming my-transformer-in came from my-transformer.rkt, this breaks the code. Require transformers can only be used after they're imported.

Resyntax shouldn't bother trying to tidy requires when unknown require transformers are used. Doing something smarter is technically possible, but requires a lot of effort. Ideally the code would be refactored to have a completely separate (require "my-transformer.rkt") form that occurs before the module's main require form, which is the simplest way to avoid this problem in practice.

[jackfirth]

Actually I already reported this in #316 and fixed this in #319, but my fix was inadequate. It fails to detect imported require transformers used inside specs like prefix-in. The code I gave above is currently handled fine by Resyntax, it's this code that breaks:

(require "my-transformer.rkt"
         (prefix-in foo: (my-transformer-in)))

Burying the transformer inside prefix-in is enough to hide it from the naive logic Resyntax currently uses.

[jackfirth]

Note that #10 would help here, since the issue is rare in practice and all I want Resyntax to do is leave code like this unchanged.