export type Result<T> = T | Promise<T>;
export declare function isPromise(x: any): boolean;
export declare function then<T, R>(x: Result<T>, f: (x: T) => Result<R>, onError?: (e: any) => void): Result<R>;
export declare function thenF<T, R>(f: () => Result<T>, q: (x: T) => Result<R>, onError?: (e: any) => void): Result<R>;