type Success = { kind: "ok"; value: string };
type Failure = { kind: "err"; error: Error };
type Result = Success | Failure;

function handle(result: Result): string {
  switch (result.kind) {
    case "ok":
      return result.value.toUpperCase();
    case "err":
      return `failed: ${result.error.message}`;
    default: {
      const _exhaustive: never = result;
      return _exhaustive;
    }
  }
}

function label(input: string | number | { name: string }): string {
  if (typeof input === "string") return input.trim();
  if (typeof input === "number") return input.toFixed(2);
  if ("name" in input) return input.name;
  return "unknown";
}

function readId(payload: unknown): number | null {
  if (typeof payload !== "object" || payload === null) return null;
  if (!("id" in payload)) return null;
  const id = (payload as { id: unknown }).id;
  return typeof id === "number" ? id : null;
}

console.log(handle({ kind: "ok", value: "hello" }));
console.log(label(42));
console.log(readId({ id: 7 }));