Method visit

src/ast/ast_derive_alias.cpp:111–114

            disabled ++;
        }
        virtual ExpressionPtr visit ( ExprAt * expr ) override {
            disabled --;
            return Visitor::visit(expr);
        }
    // in ?[] only value can alias
        virtual void preVisit ( ExprSafeAt * expr ) override {
            Visitor::preVisit(expr);