import { ErrorPredicate } from "./error-predicate";
/**
 * Normalizes an ErrorPredicate or Error constructor to an ErrorPredicate.
 *
 * @remarks
 * This internal function is used to support various signatures of `findCause`
 * and `filterCauses`. If the provided predicate function is an Error
 * contructor, this function returns a new predicate which checks if `is`
 * returns true with that constructor and the provided instance. Otherwise, this
 * simply returns the predicate function as-is.
 *
 * @param predicate - Predicate function to normalize.
 * @returns Normalized predicate function.
 */
export declare function normalizePredicate(predicate: ErrorPredicate | Function): ErrorPredicate;
/**
 * Internal function which is part of the implementation of `find`.
 * @param err - Error instance to search.
 * @param predicate - Normalized predicate function.
 * @returns First matching error, or null if none is found.
 */
export declare function findByPredicate(err: Error, predicate: ErrorPredicate): Error | null;
/**
 * Internal function which is part of the implementation of `filter`.
 * @param err - Error instance to search.
 * @param predicate - Normalized predicate function.
 * @returns Array of matched errors.
 */
export declare function filterByPredicate(err: Error, predicate: ErrorPredicate): Error[];