I'm trying to make a little EDSL that has one form that is special and needs to
be collected and later processed. I want to allow a user of the EDSL to write a
macro that expands to the special form. I have a module-begin that (so far)
looks like this:
(define-syntax (module-begin stx)
(syntax-parse stx
((_ module-contents ...)
(let-values
([(tasks other)
(partition
(syntax-parser #:literals (task-internal) ((task-internal _ ...) #t)
(_ #f))
(rest
;; Problems start here
(syntax->list
(local-expand
#'(#%plain-module-begin module-contents ...)
'module-begin
(list #'task-internal #'module* #'#%app)))))])
#`(#%module-begin
#,@other
(define all-tasks (list #,@tasks))
(process all-tasks))))))
If I don't bother with the local-expand and just use (rest (syntax->list stx)),
it works basically fine but won't treat macros that expand to task-internal
specially. I tried mapping local-expand over (syntax->list stx), but that led
to strange errors when I tried to define macros within the EDSL.
This current implementation fails because it expands too much too soon. A macro
will happily expand into (task-internal args ...), then (task-internal1 args
...), then (#%app task-internal1 args ...), and then the call to partition
won't see what it's expecting (in fact, I think it CAN'T see what it needs to,
because I suspect the local-expand of the #%plain-module-begin effectively
hides the task-internal identifier).
I added a bunch of stuff to the stop-ids list, hoping it would bail before
transforming task-internal beyond recognition, but nothing I added seemed to
work.
I also tried calling local-expand on #'(begin module-contexts ...) with the
'top-level context-v, but of course begin is automatically added to the
stop-ids list and local-expand stops right away.
Can I somehow get local-expand to only mostly expand a module? How do I do what
I'm trying to do here?
Thanks!
Lucas Paul
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