ref.el

(defun ref-define (type-symbol getter setter)                                   
  (put type-symbol 'ref-getter getter)                                          
  (put type-symbol 'ref-setter setter))                                         
                                                                                
(defun ref (obj &rest args)                                                     
  (apply (get (type-of obj) 'ref-getter)                                        
         obj                                                                    
         args))                                                                 
                                                                                
(gv-define-simple-setter                                                        
 ref                                                                            
 (lambda (obj &rest args)                                                       
   (apply (get (type-of obj) 'ref-setter)                                       
          obj                                                                   
          args)))                                                               
                                                                                
(ref-define 'hash-table                                                         
            (lambda (table key &optional default)                               
              (gethash key table default))                                      
            (lambda (table key value)                                           
              (puthash key value table)))                                       
                                                                                
(ert-deftest ref-hash-tables ()                                                 
  (let ((table (make-hash-table)))                                              
    (setf (ref table 'foo) 'bar)                                                
    (should (eq (ref table 'foo)                                                
                'bar))))