import type { DefaultPropOptions, PropOptions, RequiredPropOptions } from '../types';
import type { Validator } from '../validators';
interface FunctionPropOptionsGenerator<T> {
    optional: PropOptions<T | undefined> & {
        default?: () => T;
    };
    nullable: DefaultPropOptions<T | null> & {
        default?: (() => T) | null;
    };
    required: RequiredPropOptions<T> & {
        default?: () => T;
    };
}
/**
 * Allows any function. No further runtime validation is performed by default.
 *
 * @template T - can be used to restrict the type to a specific function signature at compile time.
 * @param validator - Optional function for further runtime validation; should return `undefined` if valid, or an error string if invalid.
 */
export declare const functionProp: <T extends Function>(validator?: Validator) => FunctionPropOptionsGenerator<T>;
export {};