import { ValidatorFn } from '@angular/forms';
export declare class CustomValidators {
    /**
     * Tests the control using Angular's required validator, except returns
     * an error map that triggers the plural 'are required' validation message
     * instead of 'is required'
     *
     * @returns An error map with the `requiredPlural` property
     * if the validation check fails, otherwise `null`.
     */
    static requiredPlural: ValidatorFn;
    /**
     * Returns a validation error if the control's value is not valid JSON.
     */
    static json: ValidatorFn;
    /**
     * Returns a validation error if the control's value is not a valid domain.
     */
    static domain: ValidatorFn;
}
