type-plus
Version:
Provides additional types for TypeScript.
49 lines • 1.21 kB
TypeScript
import type { IsAnyOrNever } from '../mix_types/any_or_never_type.js';
/**
* Check if the type `T` is exactly `true`.
*
* ```ts
* type R = TrueType<true> // true
*
* type R = TrueType<false> // never
* type R = TrueType<unknown> // never
* ```
*/
export type TrueType<T, Then = T, Else = never> = IsAnyOrNever<T, Else, [
T,
true
] extends [true, T] ? Then : Else>;
/**
* Check if the type `T` is not exactly `true`.
*
* ```ts
* type R = NotTrueType<true> // never
*
* type R = NotTrueType<false> // false
* type R = NotTrueType<unknown> // unknown
* ```
*/
export type NotTrueType<T, Then = T, Else = never> = TrueType<T, Else, Then>;
/**
* Is the type `T` exactly `true`.
*
* ```ts
* type R = IsTrue<true> // true
*
* type R = IsTrue<false> // false
* type R = IsTrue<unknown> // false
* ```
*/
export type IsTrue<T, Then = true, Else = false> = TrueType<T, Then, Else>;
/**
* Is the type `T` not exactly `true`.
*
* ```ts
* type R = IsNotTrue<true> // false
*
* type R = IsNotTrue<false> // true
* type R = IsNotTrue<unknown> // true
* ```
*/
export type IsNotTrue<T, Then = true, Else = false> = TrueType<T, Else, Then>;
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