···

       
16
       
16
       
 
       
  subscribe(observer: ObservableObserver<T>): ObservableSubscription;

     

       
17
       
17
       
 
       
}

     

       
18
       
18
       
 
       


     

       
19
       
19
       
-
       
const observableSymbol = (): symbol =>

     

       
20
       
20
       
-
       
  (Symbol as any).observable || ((Symbol as any).observable = Symbol('observable'));

     

       
19
       
19
       
+
       
const observableSymbol = (): symbol | string => Symbol.observable || '@@observable';

     

       
21
       
20
       
 
       


     

       
22
       
21
       
 
       
export function fromObservable<T>(input: Observable<T>): Source<T> {

     

       
23
       
22
       
 
       
  input = input[observableSymbol()] ? (input as any)[observableSymbol()]() : input;