[racket] Check syntax and disappearing bindings

`syntax-local-introduce' fixed the problem.

Thanks!

Vincent


At Sun, 14 Aug 2011 08:20:59 -0500,
Robby Findler wrote:
> 
> Yes, those are the properties that you want. I guess the problem is
> that the identifiers don't actually bind each other (rather than Check
> Syntax not finding the properties).
> 
> For example, this macro works fine:
> 
>   (define-syntax (m stx)
>     (syntax-case stx ()
>       [(_ id1 id2)
>        (syntax-property
>         (syntax-property
>          #`1
>          'disappeared-use (list (syntax-local-introduce #'id1)))
>         'disappeared-binding (list (syntax-local-introduce #'id2)))]))
> 
> When you put the syntax object into a property, then it doesn't get
> the cancelling mark that the expander puts on when a syntax object is
> returned from a transformer, so you have to put it on yourself. At
> least that's one way to do it.
> 
> I added a note about this to the Check Syntax section of the plugins
> manual plus a pointer to a relevant helper library.
> 
> Robby
> 
> On Fri, Aug 12, 2011 at 4:18 PM, Vincent St-Amour <stamourv at ccs.neu.edu> wrote:
> >
> > I have a macro that restructures `let' binding lists, and I would like
> > to have it play nice with Check Syntax.
> >
> > Here's an example:
> >
> > (let ([x 1.2+3.4i])
> >  body ...)
> >
> > is expanded to:
> >
> > (let ([x-real 1.2]
> >      [x-imag 3.4])
> >  body ...)
> >
> > with references to `x' replaced by references to `x-real' and `x-imag'
> > appropriately.
> >
> > The macro works fine, but causes Check Syntax to not draw arrows
> > between uses of `x' in the body and the binding occurrence of
> > `x'. Which makes sense, given that none of these are present in the
> > fully expanded code.
> >
> > It seems that the 'disappeared-binding syntax property may be what I
> > want, but I haven't figured out how to use it, and the documentation
> > does not say much about it.
> >
> > I tried adding the 'disappeared-binding property with a list
> > containing the syntax object corresponding to the binding occurrence
> > of `x' as value, and 'disappeared-use properties with the syntax
> > objects corresponding to the references to `x' that were removed.
> >
> > I tried adding these syntax properties in various places in the
> > program, but couldn't get Check Syntax to show the arrows.
> >
> > Is 'disappeared-binding what I want? If so, where do I need to put the
> > property to get Check Syntax to recognize it?
> >
> > Vincent
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