/**
 * `AsyncQueue<T>` — buffered async iterator helper.
 *
 * Producers `push` values; consumers `await next()` to receive them. Producers
 * call `close()` on clean termination or `fail(err)` on transport-level error.
 *
 * Single-consumer by design — every QAR task subscription owns one queue. If
 * you need fan-out, make N queues and push to each.
 */
export declare class AsyncQueue<T> {
    private readonly buffer;
    private readonly waiters;
    private closed;
    private terminalError;
    /** Push a value to the queue. No-op once the queue is closed. */
    push(value: T): void;
    /**
     * Mark the queue terminated cleanly. Pending and future `next()` calls
     * resolve with `{ done: true }` once the buffer drains.
     */
    close(): void;
    /**
     * Mark the queue terminated with an error. The next `next()` call (or any
     * pending one) rejects with `err`.
     */
    fail(err: Error): void;
    /** Whether the queue has been closed (cleanly or via `fail`). */
    get isClosed(): boolean;
    /** Pull the next value. Resolves on push, rejects on fail, terminates on close+drain. */
    next(): Promise<IteratorResult<T>>;
}
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