(module erase-lexical-scope mzscheme
  (require (lib "contract.ss"))
  (provide/contract (erase-lexical-scope (syntax? . -> . syntax?)))
  
  ;; erase-lexical-scope: syntax -> syntax
  ;; Removes identifier-binding information from a syntax, preserving
  ;; location information.
  (define (erase-lexical-scope stx)
    (define (syntax-properties stx)
      (map (lambda (f) (f stx)) 
           (list syntax-source syntax-line syntax-column
                 syntax-position syntax-span)))
    (syntax-case stx ()
      [()
       (datum->syntax-object #f '() stx)]
      [(a . b)
       (let ([ea (erase-lexical-scope #'a)]
             [eb (erase-lexical-scope #'b)])
         (datum->syntax-object #f `(,ea . ,eb) (syntax-properties stx)))]
      [_
       (datum->syntax-object 
        #f (syntax-object->datum stx) (syntax-properties stx))])))