import { AsyncFunction } from "../types";
export declare class _SynchronousQueue {
    private _taskHandles;
    private _runningOrRunScheduled;
    private _draining;
    constructor();
    runTask(task: AsyncFunction): Promise<unknown>;
    queueTask(task: AsyncFunction): void;
    flush(): Promise<void>;
    drain(): Promise<void>;
    _scheduleRun(): void;
    _run(): Promise<void>;
}