On 12-10-2022 23:51, Csepp wrote:
> And yes, the error message could be clearer,
> although I'm not sure where that should be fixed.

How about in the Guix code that uses the semver stuff?

> Guile doesn't know
> what packages correspond to what modules and it should probably stay
> that way.

It doesn't need to know, e.g. Guix could do

(define-module (whatever) #:autoload (bar) (foo))

(define (foo-if-available)
   (catch 'unbound-variable
     (lambda () foo)
     (lambda _ #false)))

[...]

(define (stuff)
   (define foo (foo-if-available))
   (unless foo
     (error "To use \"guix import crate\", you need to install 
guile-semver"))
   [... use foo ...])

Greetings,
Maxime.