/**
 * Wraps an async function so that concurrent calls share the same in-flight
 * Promise. Once the Promise settles, the next call starts fresh.
 *
 * @param fn - The async function to guard against concurrent execution
 * @returns {Function} A wrapped version of fn that never runs concurrently with itself
 */
export declare function singleFlight<T>(fn: () => Promise<T>): () => Promise<T>;