hkt-toolbelt/type/is-never.d.ts

Functional and composable type utilities

import { Conditional, Kind } from '..';
/**
 * `_$isNever` is a type-level function that checks if a type is `never`.
 *
 * @template X - The type to check.
 *
 * @example
 * type T0 = _$isNever<'1'> // false
 * type T1 = _$isNever<never> // true
 * type T2 = _$isNever<unknown> // false
 * type T3 = _$isNever<any> // false
 */
export type _$isNever<X> = Conditional._$equals<X, never>;
/**
 * `IsNever` is a type-level function that checks if a type is `never`.
 *
 * @template X - The type to check.
 *
 * @example
 * type T0 = $<IsNever, '1'> // false
 * type T1 = $<IsNever, never> // true
 * type T2 = $<IsNever, unknown> // false
 * type T3 = $<IsNever, any> // false
 */
export interface IsNever extends Kind.Kind {
    f(x: this[Kind._]): _$isNever<typeof x>;
}