type never - nberlette/is GitHub Wiki

@nick/is/type/never

IsNever

Signature

export type IsNever<T, True = true, False = false> = [T] extends [never] ? True
  : False;

Check if the type T is specifically never, returning True if it is, and False if not.

Type Parameters
  • T
  • True (default: true)
  • False (default: false)
Category

Types

Examples

import type { IsNever } from "@nick/is/type/never";

type A = IsNever<never>; // true
type B = IsNever<never, "never", "not never">; // "never"

OmitNever

Signature

export type OmitNever<T, Deep extends boolean = false> = T extends object ? {
         [K in [object Object]]: Deep extends true ? OmitNever<T[K], Deep> : T[K]
    } : T;

Omit properties from an object type where the value is never.

This relies on the IsNever utility type.

Type Parameters
  • T
  • Deep extends boolean (default: false)
Category

Types

Examples

import type { OmitNever } from "@nick/is/type/never";

type A = Required<{ a: string; b: number } & { b: bigint; c: number }>;
//   ^? type A = { a: string; b: never; c: number }

type B = OmitNever<A>;
//   ^? type B = { a: string; c: number }
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