00059-hard-get-optional.ts

// ============= Test Cases =============
import type { Equal, Expect } from './test-utils'

type cases = [
  Expect<Equal<GetOptional<{ foo: number; bar?: string }>, { bar?: string }>>,
  Expect<
    Equal<GetOptional<{ foo: undefined; bar?: undefined }>, { bar?: undefined }>
  >
]

// ============= Your Code Here =============
type GetOptional<T> = {
  [P in keyof T as T[P] extends Required<T>[P] ? never : P]: T[P]
}

type Test = GetOptional<{ foo: number; bar?: string }>