Method visit

src/ast/ast_generate.cpp:904–907

            scopes.push_back(block);
        }
        virtual ExpressionPtr visit ( ExprBlock * block ) override {
            scopes.pop_back();
            return Visitor::visit(block);
        }
        virtual void preVisit ( ExprFor * expr ) override {
            Visitor::preVisit(expr);
            if ( scopes.size()==0 ) {   // only top level for loop