I was working with a few friends, and we came across the following
behavior: simple usage of the syntax pattern matching system doesn't
seem to preserve the syntax location of syntax objects under certain
conditions.
Here's an example to demonstrate:
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
#lang racket
(define x (datum->syntax #f 'hello (list 'my-source 3 3 18 5)))
(define y (datum->syntax #f 'world (list 'my-source 3 9 24 5)))
(define a-bigger-syntax #`(module foo racket/base (#%module-begin #,x #,y)))
(define a-reconstructed-syntax
(syntax-case a-bigger-syntax ()
[(module name language (a-modbeg body ...))
#'(module name language (a-modbeg body ...))]))
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
When we inspect the syntax locations in a-reconstructed-syntax, we see
funkiness associated with the locations of the body elements.
We've isolated the issue down to the use of ...; if we do the
following, things look slightly better, but the location of the
'world' is still messed up.
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(define another-reconstructed-syntax
(syntax-case a-bigger-syntax ()
[(module name language (a-modbeg . body))
#'(module name language (a-modbeg . body))]))
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
I guess I'm trying to say: I don't understand the behavior of syntax
and syntax-case, with regards to how they preserve the source
locations of the matched sub-elements.
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