message: refactor(mergeMap): ensure buffered values are released.
diff: @@ -109,7 +109,13 @@ export function mergeMap<T, R, O extends ObservableInput<any>>(
  * Called to check to see if we can complete, and completes the result if
  * nothing is active.
  */
  - const checkComplete = () => isComplete && !active && subscriber.complete();
  + const checkComplete = () => {
  + if (isComplete && !active) {
  + subscriber.complete();
  + // Ensure any buffered values are released.
  + buffer = null!;
  + }
  + };
  /**
  * Attempts to start an inner subscription from a buffered value,
  