interactions

> (define x 1)
> (set! x 2)
> (set! x 3)
> global
#<mutable-free-id-table>
> (for/list ([(k v) (in-dict global)]) (list k v))
'((.#<syntax:4:8 x> 3))

tracking-set.rkt

#lang racket

(require syntax/id-table (only-in racket [set! #%set!]))

(define global (make-free-id-table))

(define-syntax-rule (location-of id) #'id)

(define-syntax-rule (set! id expr)
  (let ([v expr])
    (dict-set! global (location-of id) v)
    (#%set! id v)))