refactor(MergeMap): clarify any types which are used in MergeMapSubsc…

…riber (#1748)

* refactor(mergeMap): make MergeMapSubscriber._notifyResultSelector() private

* refactor(MergeMap): make the type of MergeMapSubscriber.buffer correctly.

* refactor(MergeMap): clarify arguments' types of MergeMapSubscriber._innerSub()

src/operator/mergeMap.ts

@@ -92,7 +92,7 @@ export class MergeMapOperator<T, I, R> implements Operator<T, I> {
  */
 export class MergeMapSubscriber<T, I, R> extends OuterSubscriber<T, I> {
  private hasCompleted: boolean = false;
- private buffer: Observable<any>[] = [];
+ private buffer: T[] = [];
  private active: number = 0;
  protected index: number = 0;
 
@@ -103,16 +103,16 @@ export class MergeMapSubscriber<T, I, R> extends OuterSubscriber<T, I> {
  super(destination);
  }
 
- protected _next(value: any): void {
+ protected _next(value: T): void {
  if (this.active < this.concurrent) {
  this._tryNext(value);
  } else {
  this.buffer.push(value);
  }
  }
 
- protected _tryNext(value: any) {
- let result: any;
+ protected _tryNext(value: T) {
+ let result: ObservableInput<I>;
  const index = this.index++;
  try {
  result = this.project(value, index);
@@ -124,7 +124,7 @@ export class MergeMapSubscriber<T, I, R> extends OuterSubscriber<T, I> {
  this._innerSub(result, value, index);
  }
 
- private _innerSub(ish: any, value: T, index: number): void {
+ private _innerSub(ish: ObservableInput<I>, value: T, index: number): void {
  this.add(subscribeToResult<T, I>(this, ish, value, index));
  }
 
@@ -145,7 +145,7 @@ export class MergeMapSubscriber<T, I, R> extends OuterSubscriber<T, I> {
  }
  }
 
- _notifyResultSelector(outerValue: T, innerValue: I, outerIndex: number, innerIndex: number) {
+ private _notifyResultSelector(outerValue: T, innerValue: I, outerIndex: number, innerIndex: number) {
  let result: R;
  try {
  result = this.resultSelector(outerValue, innerValue, outerIndex, innerIndex);