const xx=ref<State>({yy:x}) xx.value 类型不等于State吗？

const xx=ref<State>({yy:x})  xx.value 类型不等于State吗？  

type State ={  
yy:string;  
}  
type ResultObj={  
   state:State;  
}  
const xx=ref<State>({yy:'xx'})    

function result():ResultObj{  

  return {  
    state:xx.value  

   } as ResultObj  

}  

**
异常：

error: java.lang.ClassCastException: io.dcloud.uniapp.vue.UTSReactiveJSONObject cannot be cast to uni.UNIC2451D5.State‌**