/**
 * Recursive helper type to extract the innermost non-array element types from T.
 * Handles nested arrays and unions of arrays/non-arrays.
 */
type FlattenElement<T> = T extends ReadonlyArray<infer U> ? FlattenElement<U> : T;
/**
 * Flattens an array of arrays with unknown depth into a single-level array.
 *
 * @template T The type of the potentially nested array. Must extend `readonly unknown[]`.
 *
 * @param array The array to flatten.
 *
 * @returns A new, single-level array containing all the innermost elements
 * extracted from the input array. The element type is inferred recursively.
 */
export declare const flattenDeep: <T extends ReadonlyArray<unknown>>(array: T) => FlattenElement<T>[];
export {};