Type Alias IsNever<T>

Example

import type {IsNever} from 'type-fest';

type And<A, B> =
	A extends true
		? B extends true
			? true
			: false
		: false;

// https://github.com/andnp/SimplyTyped/blob/master/src/types/strings.ts
type AreStringsEqual<A extends string, B extends string> =
	And<
		IsNever<Exclude<A, B>> extends true ? true : false,
		IsNever<Exclude<B, A>> extends true ? true : false
	>;

type EndIfEqual<I extends string, O extends string> =
	AreStringsEqual<I, O> extends true
		? never
		: void;

function endIfEqual<I extends string, O extends string>(input: I, output: O): EndIfEqual<I, O> {
	if (input === output) {
		process.exit(0);
	}
}

endIfEqual('abc', 'abc');
//=> never

endIfEqual('abc', '123');
//=> void
Copy