import type { AnyService, UnknownService } from "../service/index.js";
import type { Layer } from "./index.js";
/**
 * Two {@link Layer}s chained together.
 */
export declare class Stack<In extends AnyService = UnknownService, Mid extends AnyService = UnknownService, Out extends AnyService = UnknownService> implements Layer<Out, In> {
    private readonly inner;
    private readonly outer;
    /**
     * Creates a new {@link Stack}.
     */
    constructor(inner: Layer<Mid, In>, outer: Layer<Out, Mid>);
    layer(service: In): Out;
}