import { BaseError } from 'make-error';
import { Constrained } from '../../core';
export declare class InvalidMailtoError extends BaseError {
    constructor();
}
export declare const mailtoSymbol: unique symbol;
export type Mailto = Constrained<typeof mailtoSymbol, string>;
export declare function isMailto(input: unknown): input is Mailto;
export declare function mailto(input: unknown): Mailto;