/**
 * 🎯 Decorator `@mutex` ensures that an async method never runs concurrently.
 *
 * Every invocation of the decorated method is executed strictly one at a time.
 * If the method is called again while a previous call is still running,
 * the new call will wait in a queue until all earlier calls have finished.
 *
 * Unlike `@singleflight`, this decorator:
 * - Does NOT return the same Promise for concurrent calls;
 * - Runs every invocation independently with its own arguments and result;
 * - Guarantees that each call will eventually execute - queued behind previously scheduled ones.
 *
 * Usage:
 * ```typescript
 * class Example {
 *   @mutex async save(data: string): Promise<void> { ... }
 * }
 *
 * const e = new Example();
 * e.save('A'); // runs immediately
 * e.save('B'); // waits until A finishes
 * e.save('C'); // waits until B finishes
 * // start A → end A → start B → end B → start C → end C
 * ```
 */
export declare function mutex<A extends Array<unknown>, R extends Promise<unknown>>(value: unknown, context: ClassMethodDecoratorContext<object, (...args: A) => R>): (...args: A) => R;
export declare function mutex<A extends Array<unknown>, R extends Promise<unknown>>(value: unknown, context: ClassFieldDecoratorContext<object, (...args: A) => R>): (originalFn: (...args: A) => R) => (...args: A) => R;