type-plus/esm/never/never_type.d.ts

Provides additional types for TypeScript.

import type { Brand } from '../nominal/brand.js';
/**
 * This is a unique type used in the `Else` branch of `NeverType`.
 */
export type Not_Never = Brand<'not_never', symbol>;
/**
 * This is a unique type used in the `Else` branch of `NotNeverType`.
 */
export type Is_Never = Brand<'is_never', symbol>;
/**
 * Check if `T` is `never`.
 * If it is not, returns `Not_Never`.
 *
 * ```ts
 * type R = NeverType<never> // never
 *
 * type R = NeverType<1> // 'not never'
 * ```
 */
export type NeverType<T, Then = T, Else = Not_Never> = [T, never] extends [never, T] ? Then : Else;
/**
 * Check if `T` is not `never`.
 * If it is not, returns `Is_Never`.
 *
 * ```ts
 * type R = NotNeverType<1> // 1
 *
 * type R = NotNeverType<never> // 'is_never'
 * ```
 */
export type NotNeverType<T, Then = T, Else = Is_Never> = NeverType<T, Else, Then>;
/**
 * Is `T` `never`.
 *
 * ```ts
 * type R = IsNever<never> // true
 *
 * type R = IsNever<1> // false
 * ```
 */
export type IsNever<T, Then = true, Else = false> = NeverType<T, Then, Else>;
/**
 * Is `T` not `never`.
 *
 * ```ts
 * type R = IsNotNever<1> // true
 *
 * type R = IsNotNever<never> // false
 */
export type IsNotNever<T, Then = true, Else = false> = NeverType<T, Else, Then>;
export declare namespace NeverType {
    /**
     * Type options when input type is `never`.
     */
    interface Options {
        caseNever?: unknown;
    }
    interface DefaultOptions {
        caseNever: never;
    }
}
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