import { Schema } from "../schema.js";
/**
 * Checks if the value is a primitive `boolean`; `true` or `false`
 * @example
 * ```ts
 * guard(true, $boolean); // ok
 * guard(false, $boolean); // ok
 * guard(1, $boolean); // will throw a `TypeError`
 * ```
 */
export declare const $boolean: Schema<boolean>;
/**
 * Checks if the value is `NaN` using `Number.isNaN`
 * @remarks
 * Unlike most other numbers, `NaN` cannot be used as a literal type, so this function
 * can only narrow the type to `number`
 * @internalRemarks
 * There are a couple issues tracking this and other adjacent problems
 * - <https://github.com/microsoft/TypeScript/issues/28682>
 * - <https://github.com/microsoft/TypeScript/issues/32277>
 * - <https://github.com/microsoft/TypeScript/issues/36964>
 * @example
 * ```ts
 * guard(NaN, $NaN); // ok
 * guard(0, $NaN); // throws a `TypeError` because `0` is not `NaN`
 * ```
 */
export declare const $NaN: Schema<number>;
/**
 * Alias for {@link $literal | `$literal(false)`}
 */
export declare const $false: Schema<false>;
/**
 * Alias for {@link $literal | `$literal(true)`}
 */
export declare const $true: Schema<true>;
/**
 * Alias for {@link $literal | `$literal(undefined)`}
 */
export declare const $undefined: Schema<undefined>;
/**
 * Alias for {@link $literal | `$literal(null)`}
 */
export declare const $null: Schema<null>;