[racket] Passing information between syntax classes

Konrad, 

Adding the super-bar syntax-class below 
and the following #with directive to the foo syntax class

#:with sb:super-bar   #'((foo-symbol ...) (bar.symbol ...))

should accomplish what you want without recourse to explicit parameters

Let me know if you need/want further discussion.

Thanks

R./Zack

#lang racket

(require (for-syntax syntax/parse))

(define-syntax (foos-of-bars stx)

  (define-syntax-class bar
    (pattern ((~datum bar) symbol:id)))
    
  (define-syntax-class super-bar
    #:attributes (value)
    (pattern ((foo-symbol:id ...)(bar-symbol:id ...))
             #:with value  #'(let ([foo-symbols (set (quote foo-symbol) ...)])
                                 (list 'bar
                                       (if (set-member? foo-symbols (quote
bar-symbol))
                                           (list (quote bar-symbol))
                                           (quote bar-symbol))
                                       ...))))
                       
  
  (define-syntax-class foo
    #:attributes (value)
    (pattern ((~datum foo) foo-symbol:id ... bar:bar ...)
             #:with sb:super-bar   #'((foo-symbol ...) (bar.symbol ...))
             #:with value         #'(list 'foo sb.value)))
                       
             
  (syntax-parse stx
    [(_ foo:foo ...)
      #'(list foo.value ...) ]))
  
(foos-of-bars (foo x y (bar a) (bar x)))
;->'((foo (bar a (x))))