anchor.diff:    }
   
     @override
  -  Type _visit(
  -      Harness h, FlowAnalysis<Node, Statement, Expression, Var, Type> flow) {
  -    var type = expr._visit(h, flow);
  -    flow.parenthesizedExpression(this, expr);
  +  Type _visit(Harness h) {
  +    var type = expr._visit(h);
  +    h._flow.parenthesizedExpression(this, expr);
       return type;
     }
   }
  
positive.code:   }
  
    @override
    Type _visit(
        Harness h, FlowAnalysis<Node, Statement, Expression, Var, Type> flow) {
      target._visit(h, flow);
      flow.asExpression_end(target, type);
      return type;
    }
  }
  
negative.code:   void _preVisit(AssignedVariables<Node, Var> assignedVariables) {}
  
    @override
    Type _visit(Harness h) => type;
  }
  
  class _Property extends LValue {
  