Extends

import type { Extends } from '@dr.pogodin/react-utils';
                  // or from '@dr.pogodin/js-utils';

type Extends<Base, T extends Base> = T;

The Extends generic validates compile-time that the type T extends (is assignable to) the given Base type. It returns T for chaining if the validation passes; otherwise it causes compilation error.

BEWARE: In case Base has some optional fields, T may still extends Base without having them; if you want to validate that T has all fields declared in Base, you should use Implements instead.