/**
 * A container object which may or may not contain a non-`nullish` value.
 *
 * @template TValue The type of value.
 */
export declare class Optional<TValue> {
    #private;
    private constructor();
    /**
     * Returns an empty `Optional` instance. No value is present for this `Optional`.
     *
     * @template TValue The type of value.
     * @returns {Optional<TValue>} An empty `Optional` instance.
     */
    static empty<TValue>(): Optional<TValue>;
    /**
     * Returns an `Optional` instance describing the given non-`nullish` value.
     *
     * @template TValue The type of value.
     * @param {TValue} value The value to describe, which must be non-`nullish`.
     * @returns {Optional<TValue>} An `Optional` instance with the value present.
     * @throws {TypeError} If value is `nullish`.
     */
    static of<TValue>(value: TValue): Optional<TValue>;
    /**
     * Returns an `Optional` instance describing the given value, if non-`nullish`,
     * otherwise returns an empty `Optional` instance.
     *
     * @template TValue The type of value.
     * @param {TValue} value The possibly-`nullish` value to describe.
     * @returns {Optional<TValue>} An `Optional` instance with a present value if the specified value is non-`nullish`,
     * otherwise an empty `Optional` instance.
     */
    static ofNullable<TValue>(value?: TValue): Optional<TValue>;
    /**
     * Indicates whether some other `Optional` instance is "equal to" this `Optional` instance.
     * The other `Optional` instance is considered equal if:
     *   - both instances have no value present or;
     *   - the present values are "equal to" each other.
     *
     * @param {Optional<TValue>} other An `Optional` instance to be tested for equality.
     * @returns {boolean} `true` if the other `Optional` instance is "equal to" this `Optional` instance, otherwise `false`.
     */
    equals(other: Optional<TValue>): boolean;
    /**
     * If a value is present, and the value matches the given `predicate`,
     * returns an `Optional` instance describing the value,
     * otherwise returns an empty `Optional` instance.
     *
     * @param {(value: TValue) => boolean} predicate The `predicate` to apply to the value, if present.
     * @returns {Optional<TValue>} An `Optional` instance describing the value of this `Optional`,
     * if a value is present and the value matches the given `predicate`, otherwise an empty `Optional` instance.
     * @throws {TypeError} If `predicate` is not a `function`.
     */
    filter(predicate: (value: TValue) => boolean): Optional<TValue>;
    /**
     * If a value is present, returns the result of applying the given `Optional`-bearing
     * mapping `function` to the value, otherwise returns an empty `Optional` instance.
     *
     * @template UValue The type of value of the `Optional` instance returned by the mapping `function`.
     * @param {(value: TValue) => Optional<UValue>} mapper The mapping `function` to apply to the value, if present.
     * @returns {Optional<UValue>} The result of applying an `Optional`-bearing mapping `function` to the value of
     * this `Optional`, if a value is present, otherwise an empty `Optional` instance.
     * @throws {TypeError} If `mapper` is not a `function` or does not return an `Optional` instance.
     */
    flatMap<UValue>(mapper: (value: TValue) => Optional<UValue>): Optional<UValue>;
    /**
     * If a value is present, returns the value, otherwise throws.
     *
     * @returns {TValue} The non-`nullish` value described by this `Optional` instance.
     * @throws {Error} If no value is present.
     */
    get(): TValue;
    /**
     * If a value is present, performs the given `action` with the value, otherwise does nothing.
     *
     * @param {(value: TValue) => void} action The `action` to be performed, if a value is present.
     * @throws {TypeError} If `action` is not a `function`.
     */
    ifPresent(action: (value: TValue) => void): void;
    /**
     * If a value is present, performs the given `action` with the value,
     * otherwise performs the given empty-based `action`.
     *
     * @param {(value: TValue) => void} action The `action` to be performed, if a value is present.
     * @param {() => void} emptyAction The empty-based `action` to be performed, if no value is present.
     * @throws {TypeError} If `action` or `emptyAction` is not a `function`.
     */
    ifPresentOrElse(action: (value: TValue) => void, emptyAction: () => void): void;
    /**
     * If a value is not present, returns `true`, otherwise `false`.
     *
     * @returns {boolean} `true` if a value is not present, otherwise `false`.
     */
    isEmpty(): boolean;
    /**
     * If a value is present, returns `true`, otherwise `false`.
     *
     * @returns {boolean} `true` if a value is present, otherwise `false`.
     */
    isPresent(): boolean;
    /**
     * If a value is present, returns an `Optional` instance describing
     * the result of applying the given mapping `function` to the value,
     * otherwise returns an empty `Optional` instance.
     *
     * @template UValue The type of the value returned from the mapping `function`.
     * @param {(value: TValue) => UValue} mapper The mapping `function` to apply to a value, if present.
     * @returns {Optional<UValue>} An `Optional` instance describing the result of applying a mapping `function`
     * to the value of this `Optional`, if a value is present, otherwise an empty `Optional` instance.
     * @throws {TypeError} If `mapper` is not a `function`.
     */
    map<UValue>(mapper: (value: TValue) => UValue): Optional<UValue>;
    /**
     * If a value is present, returns an `Optional` instance describing the value,
     * otherwise returns an `Optional` instance produced by the supplying `function`.
     *
     * @param {() => Optional<TValue>} supplier The supplying `function` that produces an `Optional` instance to be returned.
     * @returns {Optional<TValue>} An `Optional` instance describing the value of this `Optional`, if a value is present,
     * otherwise an `Optional` instance produced by the supplying `function`.
     * @throws {TypeError} If `supplier` is not a `function` or does not return an `Optional` instance.
     */
    or(supplier: () => Optional<TValue>): Optional<TValue>;
    /**
     * If a value is present, returns the value, otherwise returns other.
     *
     * @param {TValue | null} other The value to be returned, if no value is present. May be `nullish`.
     * @returns {TValue | null} The value, if present, otherwise other.
     */
    orElse(other?: TValue | null): TValue | null;
    /**
     * If a value is present, returns the value, otherwise returns the result produced by the supplying `function`.
     *
     * @param {() => TValue | null} supplier The supplying `function` that produces a value to be returned.
     * @returns {TValue | null} The value, if present, otherwise the result produced by the supplying `function`.
     * @throws {TypeError} If `supplier` is not a `function`.
     */
    orElseGet(supplier: () => TValue | null): TValue | null;
    /**
     * If a value is present, returns the value, otherwise throws.
     *
     * @returns {TValue} The non-`nullish` value described by this `Optional`.
     * @throws {Error} If no value is present.
     */
    orElseThrow(): TValue;
    /**
     * If a value is present, returns the value, otherwise throws an error produced by the error supplying `function`.
     *
     * @template TError Type of the error to be thrown.
     * @param {() => TError} errorSupplier The supplying `function` that produces an error to be thrown.
     * @returns {TValue} The value, if present.
     * @throws {TError} If no value is present.
     * @throws {TypeError} If `errorSupplier` is not a `function` or does not return an `Error` instance.
     */
    orElseGetThrow<TError extends Error>(errorSupplier: () => TError): TValue;
    /**
     * Returns a non-empty `string` representation of this `Optional` suitable for debugging.
     *
     * @returns {string} The `string` representation of this instance.
     */
    toString(): string;
}
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