Re: [Chicken-hackers] Chicken 4.13: New bug in syntax-rules

[Jörg F . Wittenberger]

On Feb 24 2018, Peter Bex wrote:

> On Mon, Jan 15, 2018 at 10:11:05PM +0100, Peter Bex wrote:
> > On Sat, Jan 13, 2018 at 03:28:09PM +0100, Jörg F. Wittenberger wrote:
> > > Hi all,
> > > 
> > > I just boiled down an issue with syntax-rules processing new in chicken
> > > 4.13.
> > > 
> > > It is a bit involved.  I needed three modules to demonstrate it.
> >
> > Good find!
> >
> > I've created ticket #1441 to track this.  It also contains a highly
> > simplified version of this situation which indeed also breaks in
> > CHICKEN 4.13 but not 4.12.
>
> Hi again,
>
> I did some more research into this bug, and I'm less and less convinced
> it's really a bug.  See my findings in the ticket.

If it's not a bug, then I'd need another word to excuse my embarrassment. 
After all such code used to work for several years (since define-macros 
went away) until 4.13 came along, broke it and the bug reports I got where: 
"your code does not even compile!!1!".

I'm not sure that this is "undefined behavior" in the spec. Even though 
some other Schemes have implementation issues too. Your findings in the 
ticket seem to indicate that at least Chibi does the right thing, as did 
4.12.

> We may be able to make it work, but I don't see how just yet.

Neither see I.

However if not, we should at least document under known limitations that 
there are issues wrt. hygienic macro expansion. (After all it is not nice 
to send users spending a couple of days to hunt down situations, be them 
called a bug or a not-bug, where importing unrelated modules breaks 
things.)

Best

/Jörg