Functional utility to recover from `undefined` values

recover.ts

function recover<T, F, A extends any[]>(
  fn: (...args: A) => T | undefined,
  fallback: () => F
): (...args: A) => T | F;
function recover<T, F>(value: T | undefined, fallback: () => F): T | F;
function recover<T, F, A extends any[]>(
  valueOrFn: T | undefined | ((...args: A) => T | undefined),
  fallback: () => F
): T | F | ((...args: A) => T | F) {
  if (typeof valueOrFn === "function") {
    return (...args: A) => {
      const result = (valueOrFn as (...args: A) => T | undefined)(...args);
      return result === undefined ? fallback() : result;
    };
  } else {
    return valueOrFn === undefined ? fallback() : valueOrFn;
  }
}