react-querybuilder/dist/types-esm/types/type-fest/is-never.d.mts

React Query Builder component for constructing queries and filters, with utilities for executing them in various database and evaluation contexts

/**
Returns a boolean for whether the given type is `never`.

@link https://github.com/microsoft/TypeScript/issues/31751#issuecomment-498526919
@link https://stackoverflow.com/a/53984913/10292952
@link https://www.zhenghao.io/posts/ts-never

Useful in type utilities, such as checking if something does not occur.

@example
```
import type {IsNever, And} from 'type-fest';

// 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
```

@group type-fest
*/
export type IsNever<T> = [T] extends [never] ? true : false;