[Allow `update-foreign-relation-object' on non-persistent instances
clinton@unknownlamer.org**20100617231348
 Ignore-this: b68eca42c9de457756b25e8f27ca02bc
 * Ends up as a noop, but this simplifies some code elsewhere
] {
hunk ./src/foreign-relation-slots.lisp 69
-  (assert (and (persistentp dao)
-	       (persistentp foreign-dao)
-	       (table-name-compatible-with-slot slot foreign-dao))
+  (assert (table-name-compatible-with-slot slot foreign-dao)
hunk ./src/foreign-relation-slots.lisp 71
-	  "Dragons: ~A ~A ~A" dao slot foreign-dao)
+	  "Table name incompatible with slot: ~A ~A ~A" dao slot foreign-dao)
hunk ./src/foreign-relation-slots.lisp 75
-    (pushnew foreign-dao (%foreign-mods-update %fm))
-    (when-bind obsolete-dao (find foreign-dao
-				  (slot-value dao (slot-definition-name slot))
-				  :test (lambda (e1 e2) (and (db= e1 e2)
-							(not (eq e1 e2)))))
-      (setf (slot-value dao (slot-definition-name slot))
-	    (nsubst foreign-dao obsolete-dao
-		    (slot-value dao (slot-definition-name slot)))))
+    (cond ((persistentp foreign-dao)
+	   (assert (persistentp dao)
+		   (dao)
+		   "Cannot update persistent foreign reference ~A to non-persistent object ~A"
+		   foreign-dao dao)
+	   (if-bind obsolete-dao (find foreign-dao
+				       (slot-value dao
+						   (slot-definition-name slot))
+				       :test (lambda (e1 e2) (and (db= e1 e2)
+							     (not (eq e1 e2)))))
+	     (progn (setf (slot-value dao (slot-definition-name slot))
+			  (nsubst foreign-dao obsolete-dao
+				  (slot-value dao (slot-definition-name slot))))
+		    (pushnew foreign-dao (%foreign-mods-update %fm)))
+	     (error "Foreign reference ~A not found in object ~A (~A)"
+		    foreign-dao dao (slot-value dao (slot-definition-name slot)))))
+	  ((not (persistentp dao))
+	   (unless (find foreign-dao (%foreign-mods-insert %fm)
+			 :key #'car)
+	     (error
+	      "Foreign reference ~A not previously inserted in object ~A (~A)"
+	      foreign-dao dao (slot-value dao (slot-definition-name slot)))))
+	  (t (error "Object ~A and reference ~A must both be non-persistent or persistent" dao foreign-dao)))
}