chore(concatAll): make concatAll operator signature more precise

Author: jinroh

src/CoreOperators.ts

@@ -15,7 +15,7 @@ export interface CoreOperators<T> {
   combineAll?: <R>(project?: (...values: Array<any>) => R) => Observable<R>;
   combineLatest?: <R>(...observables: Array<Observable<any> | ((...values: Array<any>) => R)>) => Observable<R>;
   concat?: <R>(...observables: (Observable<any> | Scheduler)[]) => Observable<R>;
-  concatAll?: () => Observable<any>;
+  concatAll?: () => Observable<T>;
   concatMap?: <R>(project: ((x: T, ix: number) => Observable<any>), projectResult?: (x: T, y: any, ix: number, iy: number) => R) => Observable<R>;
   concatMapTo?: <R>(observable: Observable<any>, projectResult?: (x: T, y: any, ix: number, iy: number) => R) => Observable<R>;
   count?: (predicate?: (value: T, index: number, source: Observable<T>) => boolean, thisArg?: any) => Observable<number>;

src/operators/concatAll.ts

@@ -12,6 +12,6 @@ import { MergeAllOperator } from './mergeAll-support';
  *
  * @returns {Observable} an observable of values merged from the incoming observables.
  */
-export default function concatAll(): Observable<any> {
+export default function concatAll<T>(): Observable<T> {
   return this.lift(new MergeAllOperator(1));
 }