Solution to Simple Vue by Anthony Fu (@antfu) from typescript-challenge

VueSimple.ts

type ToGetter<T> = {
  [P in keyof T]: T[P] extends (...args: any) => any ? ReturnType<T[P]> : never;
}

interface VueOptions<D, C, M> {
  data: () => D;
  computed: C;
  methods: M;
}

declare function SimpleVue<
  D, C, M, 
  ComputedProperties = ToGetter<C>, 
  BoundThis = D & ComputedProperties & M & { data: () => D}
>(options: 
  VueOptions<D, C, M> 
  &
  ThisType<BoundThis>): any


/* _____________ Test Cases _____________ */
import type { Equal, Expect } from '@type-challenges/utils'

SimpleVue({
  data() {

    this.firstname
    this.getRandom()
    this.data()
    
    return {
      firstname: 'Type',
      lastname: 'Challenges',
      amount: 10,
    }
  },
  computed: {
    fullname() {
      return `${this.firstname} ${this.lastname}`
    },
  },
  methods: {
    getRandom() {
      return Math.random()
    },
    hi() {
      alert(this.amount)
      alert(this.fullname.toLowerCase())
      alert(this.getRandom())
    },
    test() {
      const fullname = this.fullname
      const cases: [Expect<Equal<typeof fullname, string>>] = [] as any
    },
  },
})