import { type StandardSchemaV1 } from "../../Validate/standardSchema";
export interface UndefinedReturn {
    validate: boolean;
    message: string;
    type: "undefined";
}
/**
 * Optional validator augmented with a reference to the wrapped validator,
 * used by `required()` to unwrap optional layers when rebuilding a shape
 * @template T - The type of value the wrapped validator expects
 * @template R - The return type of the wrapped validator (preserved so the inner type tag flows through)
 */
export type OptionalValidator<T, R extends {
    type: unknown;
    message: string;
    validate: boolean;
} = {
    type: unknown;
    message: string;
    validate: boolean;
}> = ((value?: T) => R | UndefinedReturn) & {
    inner: (value: T) => R;
    isOptional: true;
};
/**
 * Wraps a validator to accept undefined values
 * @template T - The type of value the wrapped validator expects
 * @template R - The return type of the wrapped validator (preserved so the inner type tag flows through)
 * @param {Function} validator - Validator function to make optional
 * @returns {OptionalValidator<T, R>} - Validator that passes for undefined or delegates to the wrapped validator
 */
export declare const optional: <T, R extends {
    type: unknown;
    message: string;
    validate: boolean;
}>(validator: (value: T) => R) => OptionalValidator<T, R> & StandardSchemaV1<T | undefined, T | undefined>;