Require copy-expression is implemented

larcs.org

@@ -101,6 +101,9 @@ Note, by default, ~eqal~ will handle ~type-error~ by trying to switch the order
         (declare (ignore err))
         (eqal expression-b expression-a))))
 
+  @export
+  (defgeneric copy-expression (expression))
+
   @export
   (defgeneric substitute-expression (expression with in))