Extract the types and properties from input literal/type/tuple of types

extract-types-properties.ts

type Decrement<N extends number> = [
  -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
  10, 11, 12, 13, 14, 15, 16, 17, 18, 19
][N];

type ExtractNthProperty<T, N extends number> =
  T extends readonly [infer First, ...infer Rest]
    ? N extends 0
      ? First
      : ExtractNthProperty<Rest, Decrement<N>>
    : never;

type ExtractPropertyByName<T, K extends keyof T> = T[K];

declare module 'typescript' {
  namespace BooleanLiteral {
    type yes = true;
    type no = false;
  }
}

type Male = { gender: 'male'; age: number };
type Female = { gender: 'female'; salary: number };
type NonBinary = { gender: 'non-binary'; pronouns: string };
type Hermaphrodite = { gender: 'hermaphrodite'; pronouns: string };
type Asexual = { gender: 'asexual'; hydra: (answer: boolean) => boolean };
type Trans = {
  gender: 'trans';
  thighHighs: (answer: BooleanLiteral.yes | BooleanLiteral.no) => boolean;
};

type Person = Male | Female | NonBinary | Hermaphrodite | Asexual | Trans;

type TestTuple = ExtractNthProperty<
  [Male, Female, NonBinary, Hermaphrodite, Asexual, Trans],
  5
>; // Trans
type TestSingle = ExtractNthProperty<
  [Person, Female, NonBinary, Hermaphrodite, Asexual, Trans],
  0
>; // Person
type TestAsexual = ExtractNthProperty<[Asexual], 0>; // Asexual
type AsexualHydra = ExtractPropertyByName<Asexual, 'hydra'>; // (answer: boolean) => boolean
type HermaphroditePronouns = ExtractPropertyByName<Hermaphrodite, 'pronouns'>; // string