Property does not exist on type

Version

4.0.0-beta.4

the console can print, but the compilation fails the check!!!

<script lang="ts">
import {Vue} from "vue-class-component";
import {useStore} from 'vuex'
import {AppState} from "@/types/state";

export default class Test extends Vue {

  private store = useStore<AppState>();

  public mounted(): void {
    console.log(this.store.state);
    console.log(this.store.state.app.count);
  }
}
</script>

[kiaking]

Please provide a valid reproduction. And also, it might be an issue with class component? Either way, we need to repro to look into it.