将两个类型合并成一个类型，第二个类型的键会覆盖第一个类型的键

例如：

type foo = {
  name: string;
  age: string;
}

type coo = {
  age: number;
  sex: string
}

type Result = Merge<foo, coo>; // expected to be {name: string, age: number, sex: string}

答案

// 答案 1
type Merge<F, S> = {
  [K in keyof F | keyof S]: K extends keyof S
    ? S[K]
    : K extends keyof F
      ? F[K]
      : never
}

// 答案 2
type Flatten<T> = { [K in keyof T]: T[K] }
type Merge<F, S> = Flatten<Omit<F, keyof S> & S>