Funny,  for guile I get,
scheme@(guile-user)> (define (f x) #`(let ((x 1)) #,x))
scheme@(guile-user)> (define-syntax m (lambda (x) (syntax-case x () ((_)
#`(let ((x 2)) #,(f #'x))))))
scheme@(guile-user)> (m)
$1 = 1

I ported the racket matcher to guile and worked in that environment, so
this illustrate the problem.
In racket the same idea will error out as you say (I did not find anything
wrong with your example).
I do prefer the racket behavior of bailing out because it can help
detecting the bug in stead of silently
behave against the intention for newbies. My original code where this issue
comes from is located in
compat/racket/match/match.scm in the syntax-parse repo at

https://gitorious.org/guile-syntax-parse/guile-syntax-parse

This is the racket matcher implemented using syntax-parse!

These bugs should have been corrected though in that code!

/Stefan

On Wed, Jul 4, 2012 at 9:47 AM, Marijn <hkBst@gentoo.org> wrote:

> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> Hi Stefan,
>
> On 03-07-12 23:52, Stefan Israelsson Tampe wrote:
> > You do not need gensyms if you try to mimic or implement my
> > suggested #. . On the other hand when if you do this
> >
> > (define (f stx) #`(let ((x 1)) #,stx))
> >
> > and use this with
> >
> > #`(let ((x 2)) #,(f #'x))
> >
> > the resulting expanded code would produce 1 which is not what you
> > want.
>
> I tried it in Racket:
>
>
> (define-for-syntax (f stx) #`(let ((x 1)) #,stx))
>
> (define-syntax (m stx)
>   (syntax-case stx ()
>     ((_) #`(let ((x 2)) #,(f #'x))) ))
>
> (m)
>
>
> but I get error messages which I don't know what to do about. Do you
> have running examples of code not producing the result you want?
>
> Marijn
> -----BEGIN PGP SIGNATURE-----
> Version: GnuPG v2.0.19 (GNU/Linux)
> Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/
>
> iEYEARECAAYFAk/z9PsACgkQp/VmCx0OL2xMNACbBJKq9nZJKTzCJbdnq0iPgJoE
> rSwAn2yJ1JTLMUn6v5ZR/PatxcGxgVrU
> =HFFX
> -----END PGP SIGNATURE-----
>