fix: check for interop subscriptions

src/internal/operators/catchError.ts

@@ -153,7 +153,10 @@ class CatchSubscriber<T, R> extends OuterSubscriber<T, T | R> {
       this._unsubscribeAndRecycle();
       const innerSubscriber = new InnerSubscriber(this, undefined, undefined);
       this.add(innerSubscriber);
-      subscribeToResult(this, result, undefined, undefined, innerSubscriber);
+      const innerSubscription = subscribeToResult(this, result, undefined, undefined, innerSubscriber);
+      if (innerSubscription !== innerSubscriber) {
+        this.add(innerSubscription);
+      }
     }
   }
 }

src/internal/operators/exhaustMap.ts

@@ -122,10 +122,13 @@ class ExhaustMapSubscriber<T, R> extends OuterSubscriber<T, R> {
   }
 
   private _innerSub(result: ObservableInput<R>, value: T, index: number): void {
-    const innerSubscriber = new InnerSubscriber(this, undefined, undefined);
+    const innerSubscriber = new InnerSubscriber(this, value, index);
     const destination = this.destination as Subscription;
     destination.add(innerSubscriber);
-    subscribeToResult<T, R>(this, result, value, index, innerSubscriber);
+    const innerSubscription = subscribeToResult<T, R>(this, result, undefined, undefined, innerSubscriber);
+    if (innerSubscription !== innerSubscriber) {
+      destination.add(innerSubscription);
+    }
   }
 
   protected _complete(): void {

src/internal/operators/mergeMap.ts

@@ -142,10 +142,13 @@ export class MergeMapSubscriber<T, R> extends OuterSubscriber<T, R> {
   }
 
   private _innerSub(ish: ObservableInput<R>, value: T, index: number): void {
-    const innerSubscriber = new InnerSubscriber(this, undefined, undefined);
+    const innerSubscriber = new InnerSubscriber(this, value, index);
     const destination = this.destination as Subscription;
     destination.add(innerSubscriber);
-    subscribeToResult<T, R>(this, ish, value, index, innerSubscriber);
+    const innerSubscription = subscribeToResult<T, R>(this, ish, undefined, undefined, innerSubscriber);
+    if (innerSubscription !== innerSubscriber) {
+      destination.add(innerSubscription);
+    }
   }
 
   protected _complete(): void {

src/internal/operators/mergeScan.ts

@@ -103,10 +103,13 @@ export class MergeScanSubscriber<T, R> extends OuterSubscriber<T, R> {
   }
 
   private _innerSub(ish: any, value: T, index: number): void {
-    const innerSubscriber = new InnerSubscriber(this, undefined, undefined);
+    const innerSubscriber = new InnerSubscriber(this, value, index);
     const destination = this.destination as Subscription;
     destination.add(innerSubscriber);
-    subscribeToResult<T, R>(this, ish, value, index, innerSubscriber);
+    const innerSubscription = subscribeToResult<T, R>(this, ish, undefined, undefined, innerSubscriber);
+    if (innerSubscription !== innerSubscriber) {
+      destination.add(innerSubscription);
+    }
   }
 
   protected _complete(): void {

src/internal/operators/onErrorResumeNext.ts

@@ -162,7 +162,10 @@ class OnErrorResumeNextSubscriber<T, R> extends OuterSubscriber<T, R> {
       const innerSubscriber = new InnerSubscriber(this, undefined, undefined);
       const destination = this.destination as Subscription;
       destination.add(innerSubscriber);
-      subscribeToResult(this, next, undefined, undefined, innerSubscriber);
+      const innerSubscription = subscribeToResult(this, next, undefined, undefined, innerSubscriber);
+      if (innerSubscription !== innerSubscriber) {
+        destination.add(innerSubscription);
+      }
     } else {
       this.destination.complete();
     }

src/internal/operators/skipUntil.ts

@@ -74,7 +74,11 @@ class SkipUntilSubscriber<T, R> extends OuterSubscriber<T, R> {
     const innerSubscriber = new InnerSubscriber(this, undefined, undefined);
     this.add(innerSubscriber);
     this.innerSubscription = innerSubscriber;
-    subscribeToResult(this, notifier, undefined, undefined, innerSubscriber);
+    const innerSubscription = subscribeToResult(this, notifier, undefined, undefined, innerSubscriber);
+    if (innerSubscription !== innerSubscriber) {
+      this.add(innerSubscription);
+      this.innerSubscription = innerSubscription;
+    }
   }
 
   protected _next(value: T) {

src/internal/operators/switchMap.ts

@@ -133,10 +133,13 @@ class SwitchMapSubscriber<T, R> extends OuterSubscriber<T, R> {
     if (innerSubscription) {
       innerSubscription.unsubscribe();
     }
-    const innerSubscriber = new InnerSubscriber(this, undefined, undefined);
+    const innerSubscriber = new InnerSubscriber(this, value, index);
     const destination = this.destination as Subscription;
     destination.add(innerSubscriber);
-    this.innerSubscription = subscribeToResult(this, result, value, index, innerSubscriber);
+    this.innerSubscription = subscribeToResult(this, result, undefined, undefined, innerSubscriber);
+    if (this.innerSubscription !== innerSubscriber) {
+      destination.add(this.innerSubscription);
+    }
   }
 
   protected _complete(): void {

src/internal/util/subscribeToResult.ts

@@ -10,20 +10,13 @@ export function subscribeToResult<T, R>(
   result: any,
   outerValue?: T,
   outerIndex?: number,
-  destination?: Subscriber<any>
-): Subscription;
-export function subscribeToResult<T, R>(
-  outerSubscriber: OuterSubscriber<T, R>,
-  result: any,
-  outerValue?: T,
-  outerIndex?: number,
-  destination: Subscriber<any> = new InnerSubscriber(outerSubscriber, outerValue, outerIndex)
-): Subscription | void {
+  destination: Subscriber<R> = new InnerSubscriber(outerSubscriber, outerValue, outerIndex)
+): Subscription | undefined {
   if (destination.closed) {
     return undefined;
   }
   if (result instanceof Observable) {
     return result.subscribe(destination);
   }
-  return subscribeTo(result)(destination);
+  return subscribeTo(result)(destination) as Subscription;
 }