/**
 * Shared utilities for async directive handling.
 *
 * @packageDocumentation
 */
/**
 * Thrown by `$fallback()` to signal that the directive wants fallback rendering.
 * The framework catches this at the directive execution boundary.
 */
export declare class FallbackSignal {
    readonly isFallbackSignal = true;
}
/**
 * Detect whether a function is async (declared with `async` keyword).
 *
 * @param fn - The function to check
 * @returns true if fn is an AsyncFunction
 */
export declare function isAsyncFunction(fn: Function): boolean;