Typescript 泛型即函数

type IsPlainObject<T extends unknown> = T extends object 
  ? T extends null  
    ? never
    : T 
  : never;
type RemoveVoid<T> = T extends void ? never : T;
type Merge<T,U> = {
  [K in Exclude<keyof T, keyof U>]: T[K]
} & U