How to type a computed property in the new composition API?

There are two different types for that.

If your computed prop is readonly:

const nameAndCountry: ComputedRef<string> = computed((): string => `The movie name is ${movieName.value} from ${country.value}`);

if it has a setter method:

const nameAndCountry: WritableComputedRef<string> = computed({
  get(): string {
    return 'somestring'
  },
  set(newValue: string): void {
    // set something
  },
});