(use-modules
 (ice-9 vlist)
 (ice-9 match)
 (gnu packages)
 (gnu packages curl))

(define-values (package-by-address
                register-package)
  (let ((table (delay (fold-packages
                       (lambda (package table)
                         (vhash-consq (object-address package)
                                      package table))
                       vlist-null))))
    (values
     (lambda (address)
       "Return package by its object ADDRESS."
       (match (vhash-assq address (force table))
         ((_ . package) package)
         (_ #f)))
     (lambda (package)
       "Register PACKAGE by its 'object-address', so that later
'package-by-address' can be used to access it."
       (set! table
             (delay (vhash-consq (object-address package)
                                 package (force table))))))))

(register-package curl)

;; This expressions errors:
(package-by-address (object-address curl))