A NonEmpty<T> type for both objects and lists

non-empty-type.ts

// Typescript playground of this gist: https://www.typescriptlang.org/play?#code/PTAEBUE8AcFMGcCwAoFAXGtQDkD2A7AUQFtoMB5AIwCsAecAPlAF5QBvFUL7nrgbQDSoAJb5QAa1iRcAMwgBdAFygACsIDG4+gBpQAhp15cAvn0nS54eShvIMcHARJlIAQQBO7gIaR6TVnzgugB0oeB88vIA3Lb2WHhEpBh+LI6JLh7evoygAD5pzhQ0frYgoIQAHl6kADYIoLGYoADCBGhe6mipHMg8sMRewjXK8GjuogDm2oZc0AAWBLAjY5PTyMalwLg0oLjiKOoEo6BeoMoJhb6t+O2d-lxs84vKAERe8AAmLxvIh-jHlDOBSSVzaHTQ9zY-UGw1Ab0+3wORy66iBFxBtGutwh3Se+CWcPeX100KGryJiNQyBA22ooFgnlw7kUSP+XQ+aKcGKx4MhPz+xyw5y5LkxYLu3UoNS85IRPxQZRqwmOewav2RoDkwvSyXwAFdiJQGfc+KAAIygXQAJlA1nVbNAE05Ot8o3G+AmJrhZpelrhVt9doVYCVo1ODPcTJZ9uOc2dl1o+sNxtSprtAq6wnjGLdky9FvkQA

// My two references:
// for lists: https://stackoverflow.com/questions/56006111/is-it-possible-to-define-a-non-empty-array-type-in-typescript
// for objs: https://stackoverflow.com/questions/40510611/typescript-interface-require-one-of-two-properties-to-exist


// Special thanks to @CaioCSdev https://github.com/CaioCSdev

/*
 * Creating non empty types for both objects and lists
 */

// Types

type AnyArray = unknown[];
type AnyObj = Record<string | number, unknown>;

type NonEmptyObj<T extends AnyObj> = {
  [K in keyof T]: Pick<T, K> & Partial<T>;
}[keyof T];

type NonEmptyArray<T> = [T, ...T[]];

type NonEmpty<T extends AnyArray | AnyObj> = T extends (infer U)[]
  ? NonEmptyArray<U>
  : T extends AnyObj
  ? NonEmptyObj<T>
  : never;



// Examples

type Contact = {
  email: string;
  phone: string;
};

//obj: ok
const a: NonEmpty<Contact> = { phone: 'asd' };
const b: NonEmpty<Contact> = { email: 'asd' };
const c: NonEmpty<Contact> = { phone: 'asd', email: 'asd' };

// obj: type error:
const d: NonEmpty<Contact> = {};
const e: NonEmpty<Contact> = { bla: 'asd' };

// list: ok
const f: NonEmpty<number> = [1, 2];
const g: NonEmpty<string> = ['1', '2'];

// list: type error:
const h: NonEmpty<number> = [];
const i: NonEmpty<string> = [1];

// Destructuring:
const fasd = ({email}:  NonEmptyObj<Contact>) => ({email})

fasd({phone: "asd"}) // valid call, returns { email: undefined }