我写了一个排序函数，想绑定一个比较函数。不幸的是，TypeScript编译器警告我比较函数的类型为unknown。
我已经尝试搜索SO: Bind function to function并在TS手册中搜索：绑定。但是，我找不到任何相关的问题。
并试图遵循声明文件中的类型：

/**
     * For a given function, creates a bound function that has the same body as the original function.
     * The this object of the bound function is associated with the specified object, and has the specified initial parameters.
     * @param thisArg The object to be used as the this object.
     * @param args Arguments to bind to the parameters of the function.
     */
    bind<T>(this: T, thisArg: ThisParameterType<T>): OmitThisParameter<T>;
    bind<T, A0, A extends any[], R>(this: (this: T, arg0: A0, ...args: A) => R, thisArg: T, arg0: A0): (...args: A) => R;
    bind<T, A0, A1, A extends any[], R>(this: (this: T, arg0: A0, arg1: A1, ...args: A) => R, thisArg: T, arg0: A0, arg1: A1): (...args: A) => R;
    bind<T, A0, A1, A2, A extends any[], R>(this: (this: T, arg0: A0, arg1: A1, arg2: A2, ...args: A) => R, thisArg: T, arg0: A0, arg1: A1, arg2: A2): (...args: A) => R;
    bind<T, A0, A1, A2, A3, A extends any[], R>(this: (this: T, arg0: A0, arg1: A1, arg2: A2, arg3: A3, ...args: A) => R, thisArg: T, arg0: A0, arg1: A1, arg2: A2, arg3: A3): (...args: A) => R;
    bind<T, AX, R>(this: (this: T, ...args: AX[]) => R, thisArg: T, ...args: AX[]): (...args: AX[]) => R;

function sorting<T>(a: T, fn: (v0: T, v1: T) => number,  b: T) {
  return fn(a, b)
}

sorting<number>.bind(null, 1, (a, b) => a + b)
//               ^ Cannot find name 'bind'.(2304)

sorting.bind<null, number, (v0: number, v1: number) => number, [b: number]>(null, 1, (a, b) => a + b)
//^ Argument of type '(b: number) => unknown' is not assignable to parameter of type //'(v0: number, v1: number) => number'.
//  Type 'unknown' is not assignable to type 'number'.(2345)

TSPlayground
而且它仍然不起作用。我在这里错过了什么吗？为什么我不能用bind参数a和fn？
附言
目前我使用箭头函数来作为一个变通办法来咖喱排序函数。