import { ThroughIterator } from "./ThroughIterator.js";
/**
 * Iterable that inspects a source iterable as it iterates.
 * - Stores: first/last yielded value, returned value, whether iteration is done, the number of items that were iterated.
 *
 * @example
 * 	const watch = new InspectIterator(iterable);
 * 	for (const next of capture) console.log("YIELDED", next);
 * 	console.log("FIRST", watch.first);
 * 	console.log("RETURNED", watch.returned);
 */
export declare class InspectIterator<T, R, N> extends ThroughIterator<T, R, N> implements Iterator<T, R, N>, Iterable<T, R, N> {
    /** Get the number of results received by this iterator so far. */
    readonly count = 0;
    /** Is the iteration done? */
    readonly done: boolean;
    /** The first yielded value (throws if the iteration yielded no values, i.e. `this.count === 0`). */
    get first(): T;
    private _first;
    /** The last yielded value (throws if the iteration yielded no values, i.e. `this.count === 0`). */
    get last(): T;
    private _last;
    /** The returned value (throws if the iteration is not done, i.e. `this.done === false`). */
    get returned(): R;
    private _returned;
    next(value: N): IteratorResult<T, R>;
    throw(thrown: unknown): IteratorResult<T, R>;
    return(value: R): IteratorResult<T, R>;
    /** Capture a result. */
    private _inspect;
}