Allow the user to impose that all slot accesses go through SLOT-VALUE, etc.

src/CHANGELOG

@@ -88,6 +88,11 @@ ECL 0.9i
    COMPUTE-SLOTS assign a location to each slot definition that has allocation
    :INSTANCE or :CLASS.
 
+ - A new defclass option, :optimize-slot-access, which defaults to T, controls
+   whether the slots accessors should address directly the values in the class
+   or use SLOT-VALUE. It should be set to NIL when one intends to redefine the
+   SLOT-*-USING-CLASS methods.
+
 * Errors fixed:
 
  - The intermediate output of the compiler is written in the directory in which

src/clos/kernel.lsp

@@ -74,6 +74,7 @@
   (defparameter +standard-class-slots+
     (append +class-slots+
 	    '((slot-table :accessor slot-table)
+	      (optimize-slot-access :initarg :optimize-slot-access :initform t)
 	      (forward)))))
 
 #.(create-accessors +standard-class-slots+ 'standard-class)

src/clos/standard.lsp

@@ -397,7 +397,8 @@ because it contains a reference to the undefined class~%  ~A"
 	   reader setter)
       (declare (fixnum index))
       (if (and (eql (slot-definition-allocation slotd) :instance)
-	       (si:fixnump index))
+	       (si:fixnump index)
+	       (slot-value standard-class 'optimize-slot-access))
 	  (setf reader #'(lambda (self)
 			   (let ((value (si:instance-ref self index)))
 			     (if (si:sl-boundp value)