index.test-d.ts

import {expectType, expectNever} from '../../../..';
import concat, {returnsNever} from '.';

expectType<string>(concat('foo', 'bar'));
expectType<number>(concat(1, 2));

expectType<any>(concat(1, 2));
expectType<string | number>(concat('unicorn', 'rainbow'));

expectType<false>(concat(1, 2) as any);

expectType<string>('' as never);
expectType<any>('' as never);

expectNever(returnsNever());
expectNever(5 as number);