message: refactor(map): a little smaller still
diff: +/** @prettier */
  import { Subscriber } from '../Subscriber';
  import { Observable } from '../Observable';
  import { OperatorFunction } from '../types';
  @@ -43,14 +44,15 @@ import { OperatorSubscriber } from './OperatorSubscriber';
  * @name map
  */
  export function map<T, R>(project: (value: T, index: number) => R, thisArg?: any): OperatorFunction<T, R> {
  - return function mapOperation(source: Observable<T>): Observable<R> {
  - return lift(source, function (this: Subscriber<R>, source: Observable<T>) {
  + return (source: Observable<T>) =>
  + lift(source, function (this: Subscriber<R>, source: Observable<T>) {
  const subscriber = this;
  // The index of the value from the source. Used with projection.
  let index = 0;
  - source.subscribe(new OperatorSubscriber(subscriber, (value: T) => {
  + source.subscribe(
  + new OperatorSubscriber(subscriber, (value: T) => {
  subscriber.next(project.call(thisArg, value, index++));
  - }))
  + })
  + );
  });
  - };
  }
  