/**
 * Invokes the candidate function and returns undefined if an error is thrown from it.
 *
 * @param candidate -
 *        The candidate function to run.
 *
 * @returns
 *        The result from candidate.  Returns undefined if candidate throws an Error.
 */
export declare function tryFallback<T>(candidate: () => T): T | undefined;
/**
 * Invokes the candidate function and returns fallback if an error is thrown from it.
 *
 * @param candidate -
 *        The candidate function to run.
 * @param fallback -
 *        The fallback value to return if candidate throws an error.
 *
 * @returns
 *        The result from candidate.  Returns fallback if candidate throws an Error.
 */
export declare function tryFallback<T>(candidate: () => T, fallback: T): T;
/**
 * Invokes the candidate function and returns undefined if an rejected promise is returned from it.
 *
 * @param candidate -
 *        The candidate function to run.
 *
 * @returns
 *        A promise that resolves with the result from candidate.  Returns undefined
 *        if candidate returns a rejected promise.
 */
export declare function tryFallbackAsync<T>(candidate: () => Promise<T>): Promise<T | undefined>;
/**
 * Invokes the candidate function and returns undefined if an rejected promise is returned from it.
 *
 * @param candidate -
 *        The candidate function to run.
 * @param fallback -
 *        The fallback value that will be returned if candidate returns a rejected promise.
 *
 * @returns
 *        A promise that resolves with the result from candidate.  Returns fallback
 *        if candidate returns a rejected promise.
 */
export declare function tryFallbackAsync<T>(candidate: () => Promise<T>, fallback: T): Promise<T>;