Currying manipulation for N-ary function.

multi-curry.ts

type Equal<X, Y> = (<T>() => T extends X ? 1 : 2) extends (<T>() => T extends Y ? 1 : 2) ? true : false;

type Curried<F> = F extends (...args: infer A) => infer R
  ? Equal<F, () => R> extends true
  ? () => R
  : (A extends [infer F, ...infer S]
    ? (arg: F) => Curried<(...rest: S) => R>
    : R
  )
  : never;

function curry<F extends (...args: any[]) => unknown>(fn: F): Curried<F> {
  if (fn.length === 0) {
    return (() => fn()) as Curried<F>;
  }
  const curried = (fn: F, ...argStack: unknown[]) => (newArg: unknown) => {
    const totalArgs = [...argStack, newArg];
    if (fn.length <= totalArgs.length) {
      return fn(...totalArgs);
    }
    return curried(fn, ...totalArgs);
  };
  return curried(fn) as Curried<F>;
}