src/pset-proto.lisp (default-slot-from-property): Maybe leave slot unbound.

If there are no DEFAULT-VALUE forms, and the property isn't set, then
leave the slot unbound.

diff --git a/src/pset-proto.lisp b/src/pset-proto.lisp
index e16e04c39c5a1f01a6b85ef11caf26de0442eb48..61793b5c5b5359e627be620265387431b212bd4d 100644 (file)
--- a/src/pset-proto.lisp
+++ b/src/pset-proto.lisp
@@ -317,7 +317,8 @@ (defmacro default-slot-from-property
    We initialize SLOT in INSTANCE.  In full: if PSET contains a property
    called NAME, then convert it to TYPE, bind the value to PVAR and evaluate
    CONVERT-FORMS -- these default to just using the property value.  If
    We initialize SLOT in INSTANCE.  In full: if PSET contains a property
    called NAME, then convert it to TYPE, bind the value to PVAR and evaluate
    CONVERT-FORMS -- these default to just using the property value.  If

-   there's no property, and the slot is named in SLOT-NAMES and currently
+   there's no property, and DEFAULT-FORMS contains at least one non-
+   declaration form, and the slot is named in SLOT-NAMES and currently

    unbound, then evaluate DEFAULT-FORMS and use their value to compute the
    slot value."
 
    unbound, then evaluate DEFAULT-FORMS and use their value to compute the
    slot value."
 


@@ -333,7 +334,8 @@ (defmacro default-slot-from-property
               (setf (slot-value ,instance ,slot)
                     (with-default-error-location (,floc)
                       ,@(or convert-forms `(,pvar))))
               (setf (slot-value ,instance ,slot)
                     (with-default-error-location (,floc)
                       ,@(or convert-forms `(,pvar))))

-              (default-slot (,instance ,slot ,slot-names)
-                ,@body)))))))
+              ,@(and body
+                     `((default-slot (,instance ,slot ,slot-names)
+                         ,@body)))))))))

 
 ;;;----- That's all, folks --------------------------------------------------
 
 ;;;----- That's all, folks --------------------------------------------------