type-plus
Version:
Provides additional types for TypeScript.
49 lines • 1.23 kB
TypeScript
import type { IsAnyOrNever } from '../mix_types/any_or_never_type.js';
/**
* Check if the type `T` is exactly `false`.
*
* ```ts
* type R = FalseType<false> // false
*
* type R = FalseType<true> // never
* type R = FalseType<unknown> // never
* ```
*/
export type FalseType<T, Then = T, Else = never> = IsAnyOrNever<T, Else, [
T,
false
] extends [false, T] ? Then : Else>;
/**
* Check if the type `T` is not exactly `false`.
*
* ```ts
* type R = NotFalseType<false> // never
*
* type R = NotFalseType<true> // true
* type R = NotFalseType<unknown> // unknown
* ```
*/
export type NotFalseType<T, Then = T, Else = never> = FalseType<T, Else, Then>;
/**
* Is the type `T` exactly `false`.
*
* ```ts
* type R = IsFalse<false> // true
*
* type R = IsFalse<true> // false
* type R = IsFalse<unknown> // false
* ```
*/
export type IsFalse<T, Then = true, Else = false> = FalseType<T, Then, Else>;
/**
* Is the type `T` not exactly `false`.
*
* ```ts
* type R = IsNotFalse<false> // false
*
* type R = IsNotFalse<true> // true
* type R = IsNotFalse<unknown> // true
* ```
*/
export type IsNotFalse<T, Then = true, Else = false> = FalseType<T, Else, Then>;
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