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/**
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
```
@category Type Guard
@category Utilities
*/
export type IsNever<T> = [T] extends [never] ? true : false;
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28 entries across 28 versions & 2 rubygems