Many responses on Stack Overflow mention that to prevent issues like
Error message: Property 'toPromise' does not exist on type 'Observable'
in Angular, you are advised to import 'rxjs/add/operator/toPromise'. I followed this advice until recently. However, while working on an Angular 4.2.4 project, I forgot to include the import and expected to encounter an error. Surprisingly, no error appeared! Upon further investigation using Chrome's developer tools, I observed that "toPromise" was present in the Observable's prototype.
This situation has led me to wonder... how did 'toPromise' end up there? Is it a recent addition to TypeScript, Angular, or rxjs?