import { StringRuleChecker } from './string-rule-checker';
import { GuardResult } from '../../core/guard-result';
/**
 * Boolean pattern.
 */
export declare const BOOLEAN_PATTERN = "^(true|false)$";
export declare class StringIsBoolean extends StringRuleChecker<{
    type: 'isBoolean';
}> {
    constructor(rule: {
        type: 'isBoolean';
    }, value: string);
    /**
     * @override
     */
    exec(): GuardResult;
    private isBoolean;
}