void visit(Expression * node) {
        VariableExpression *expr = freecad_dynamic_cast<VariableExpression>(node);

        if (expr) {
            if (expr->renameDocumentObject(oldName, newName)) {
                if (!changed) {
                    aboutToSetValue();
                    ++changed;
                }
            }
        }
    }
    void visit(Expression * node) {
        VariableExpression *expr = freecad_dynamic_cast<VariableExpression>(node);

        if (expr)
            expr->renameDocumentObject(oldName, newName);
    }