vuex uses module, and then wants to use store.state.a to report type errors in the TS file

// store/index.ts

// ...
Vue.use(Vuex);

const store: StoreOptions<RootState> = {
    modules: {
        a
    }
};

export default new Vuex.Store<RootState>(store);

// a.ts
// ...
export const state: State = {
    id: 1
};

const namespaced: boolean = true;

export const user: Module<UserState, RootState> = {
    namespaced,
    state
};

// use.ts
// TSVue
store.state.a.id // [ts] "{}" "a"  [2339]

how should I correct this so that this exception is not thrown?
Thank you!