import { of } from 'rxjs'; import { buffer } from 'rxjs/operators'; it('should infer correctly', () => { const o = of(1, 2, 3).pipe(buffer(of('foo'))); // $ExpectType Observable }); it('should enforce types', () => { const o = of(1, 2, 3).pipe(buffer()); // $ExpectError const p = of(1, 2, 3).pipe(buffer(6)); // $ExpectError });