Sorry I made a little indent error:
--8<---------------cut here---------------start------------->8---
(eval-when (eval)
(let-syntax ((redefine-syntax-transformer
(syntax-rules ()
((_ id who)
(let* ((guile-module the-root-module)
(original-transformer (macro-binding (module-ref
guile-module (quote id)))))
(module-define!
guile-module
(quote id)
(make-syntax-transformer
(quote id)
'core
(lambda (e r w s mod)
(with-exception-handler
(lambda (exn)
((@ (ice-9 exceptions) raise-exception)
(cond
(((@ (ice-9 exceptions) syntax-error?) exn)
(let* ((args (exception-args exn)))
(syntax-violation 'who
(cadr args)
(datum->syntax #f e
#:source s)
(cadddr args))))
(else
exn))))
(lambda ()
(original-transformer e r w s mod))
#:unwind? #f)))))))))
(redefine-syntax-transformer lambda lambda)
(redefine-syntax-transformer lambda* lambda)
(redefine-syntax-transformer let let)
(redefine-syntax-transformer letrec letrec)
(redefine-syntax-transformer letrec* letrec*)
(redefine-syntax-transformer case-lambda case-lambda)
(redefine-syntax-transformer case-lambda* case-lambda)))
--8<---------------cut here---------------end--------------->8---
On Fri, 23 Jan 2026, Olivier Dion <[email protected]> wrote:
> Hi Guiler!
>
> TL;DR: See the code at the end. You can put in your .guile to fix some
> syntax-violation source-location reporting when compiling.
>
> I've recently worked on something that might be good for all.
> Basically, I am sure all of us have already encountered this kind of
> error when compiling a module:
>
> foo.scm:
> +-
> 1|
> 2|
> 3|
> 4| (let () lambda)
> +-
>
> Compiling /home/old/foo.scm ...
>
> ice-9/boot-9.scm:1685:16: In procedure raise-exception:
> Syntax error:
> unknown location: lambda: bad lambda in form lambda
>
> Not very great right? "unknown location" is not very helpful.
> Furthermore, the syntax-violation is indeed the "lamda", but it happened
> inside the "let" form, not in the lambda form itself. Well, with the
> proposed fix I have, this is what you will get instead:
>
> Compiling /home/old/foo.scm ...
>
> ice-9/boot-9.scm:1685:16: In procedure raise-exception:
> Syntax error:
> /home/old/foo.scm:4:3: let: bad lambda in subform lambda of (let () lambda)
>
> Neat eh?
>
> So the idea is to re-define some of the core syntax-transformers from
> psyntax.
>
> Indeed, for some reasons, not all of the transformers in psyntax have
> proper source wrapping of forms on syntax-violation.
>
> I am not sure of the consequences here but I don't think there's much to
> it since the wrappers are forwarding the expander states to their
> original implementations anyway. Basically, it's just catching
> syntax-violation exceptions and raising new exceptions with proper
> source annotations. Hopefully I got this correctly.
>
> In the end, just put this in your .guile:
> --8<---------------cut here---------------start------------->8---
>
> (eval-when (eval)
>
> (let-syntax ((redefine-syntax-transformer
> (syntax-rules ()
> ((_ id who)
> (let* ((guile-module the-root-module)
> (original-transformer (macro-binding (module-ref
> guile-module (quote id)))))
> (module-define!
> guile-module
> (quote id)
> (make-syntax-transformer
> (quote id)
> 'core
> (lambda (e r w s mod)
> (with-exception-handler
> (lambda (exn)
> ((@ (ice-9 exceptions) raise-exception)
> (cond
> (((@ (ice-9 exceptions) syntax-error?) exn)
> (let* ((args (exception-args exn)))
> (if (syntax-violation 'who
> (cadr args)
> (datum->syntax #f e
> #:source s)
> (cadddr args))
>
> exn))))))
> (lambda ()
> (original-transformer e r w s mod))
> #:unwind? #f)))))))))
> (redefine-syntax-transformer lambda lambda)
> (redefine-syntax-transformer lambda* lambda)
> (redefine-syntax-transformer let let)
> (redefine-syntax-transformer letrec letrec)
> (redefine-syntax-transformer letrec* letrec*)
> (redefine-syntax-transformer case-lambda case-lambda)
> (redefine-syntax-transformer case-lambda* case-lambda)))
> --8<---------------cut here---------------end--------------->8---
>
> Regards,
> Olivier
> --
> Olivier Dion
> oldiob.ca
>
--
Olivier Dion
oldiob.ca
