A type safe curry function

curry.ts

type Curry = <A extends unknown[], R>(
  fn: (...arg: readonly [...A]) => R,
) => Curried<A, R>;

type Curried<A extends unknown[], R> = <T extends unknown[]>(
  ...arg: readonly [...T]
) => T extends A ? R : A extends [...T, ...infer U] ? Curried<U, R> : never;

const curry: Curry =
  <A extends unknown[], R>(fn: (...arg: readonly [...A]) => R): Curried<A, R> =>
  <T extends unknown[]>(
    ...args: readonly [...T]
  ): T extends A ? R : A extends [...T, ...infer U] ? Curried<U, R> : never =>
    fn.length <= args.length
      ? fn.apply(this, args)
      : curry(fn).bind(this, ...args);

function add(x: number, y: number, z: number): number {
  return x + y + z;
}

var a = curry(add);
var b = a(1, 2);
var c = b(3);
console.log(c);