logux-types.ts

class Post {
  title: string = ''
  text: string = ''
}

class Group {
  title: string = ''
  roles: string = ''
}

class User {
  login: string = ''
  age: string = ''
  group: Group = new Group()
  posts: Post[] = []
}

type Class = new (...args: any) => any

type Fields<I extends InstanceType<Class>> = {
  [key in keyof I]?: I[key] extends object[]
    ? boolean | Fields<I[key][0]>
    : I[key] extends object
    ? boolean | Fields<I[key]>
    : boolean
}

type DeepPick<I, F extends Fields<I>> = {
  [key in keyof I]: I[key] extends object[]
    ? DeepPick<I[key][0], F[key]>[]
    : I[key] extends object
    ? DeepPick<I[key], F[key]>
    : F[key] extends true
    ? I[key]
    : never
}

function useMap<K extends Class, F extends Fields<InstanceType<K>>> (
  cls: K,
  fields: F
): [false, DeepPick<InstanceType<K>, F>] | [true | null] {
  return {} as any
}

const fields: Fields<User> = {
  login: true
}

const [isLoading, user] = useMap(User, {
  login: true,
  group: {
    title: true
  },
  posts: {
    title: true
  }
})

if (user) {
  // Positive
  user.login = 'a'
  user.group.title = ''
  user.posts.forEach(post => {
    post.title = 'Test'
  })

  // Negative
  user.age = 21
  user.group.roles = ''
  user.posts.forEach(post => {
    post.text = 'Test'
  })
}