anchor.diff:      } else {
         impactBuilder.registerTypeUse(new TypeUse.asCast(type));
       }
  -    registerSeenClasses(node.type);
       visitNode(node.operand);
     }
   
  
positive.code: 
      InterfaceType type = elementMap.createInterfaceType(
          target.enclosingClass, node.arguments.types);
      classEnsurer.ensureClassesInType(type);
      CallStructure callStructure = elementMap.getCallStructure(node.arguments);
      impactBuilder.registerStaticUse(isConst
          ? new StaticUse.constConstructorInvoke(constructor, callStructure, type)
  
negative.code:   void visitIsExpression(ir.IsExpression node) {
      impactBuilder.registerTypeUse(
          new TypeUse.isCheck(elementMap.getDartType(node.type)));
      visitNode(node.operand);
    }
  
  