/**
 * Ensures that the array has at least one element. If not it returns `undefined`.
 *
 * @todo: Remove when Typescript can infer this
 * @see https://github.com/microsoft/TypeScript/issues/29841
 */
export declare const atLeastOne: <T>(array: T[]) => [T, ...T[]] | undefined;
export declare const mustHaveAtLeastOne: <T>(array: T[]) => [T, ...T[]];