fix: forkJoin POJO signature should match only ObservableInput values

api_guard/dist/types/index.d.ts

@@ -165,6 +165,7 @@ export declare type Falsy = null | undefined | false | 0 | -0 | 0n | '';
 
 export declare function firstValueFrom<T>(source: Observable<T>): Promise<T>;
 
+export declare function forkJoin(scheduler: null | undefined): Observable<never>;
 export declare function forkJoin(sources: readonly []): Observable<never>;
 export declare function forkJoin<A extends readonly unknown[]>(sources: readonly [...ObservableInputTuple<A>]): Observable<A>;
 export declare function forkJoin<A extends readonly unknown[], R>(sources: readonly [...ObservableInputTuple<A>], resultSelector: (...values: A) => R): Observable<R>;
@@ -173,7 +174,7 @@ export declare function forkJoin<A extends readonly unknown[], R>(...sourcesAndR
 export declare function forkJoin(sourcesObject: {
     [K in any]: never;
 }): Observable<never>;
-export declare function forkJoin<T>(sourcesObject: T): Observable<{
+export declare function forkJoin<T extends Record<string, ObservableInput<any>>>(sourcesObject: T): Observable<{
     [K in keyof T]: ObservedValueOf<T[K]>;
 }>;
 

spec-dtslint/observables/forkJoin-spec.ts

@@ -72,6 +72,12 @@ describe('forkJoin({})', () => {
     const obj = { foo: of(1), bar: of('two'), baz: of(false) };
     const res = forkJoin(obj); // $ExpectType Observable<{ foo: number; bar: string; baz: boolean; }>
   });
+
+  it('should reject non-ObservableInput values', () => {
+    const obj = { answer: 42 };
+    const res = forkJoin(obj); // $ExpectError
+
+  });
 });
 
 describe('forkJoin([])', () => {

spec/observables/forkJoin-spec.ts

@@ -471,11 +471,11 @@ describe('forkJoin', () => {
     it('should have same v5/v6 throwing behavior full argument of null', (done) => {
       rxTestScheduler.run(() => {
         // It doesn't throw when you pass null
-        expect(() => forkJoin(null)).not.to.throw();
+        expect(() => forkJoin(null as any)).not.to.throw();
 
         // It doesn't even throw if you subscribe to forkJoin(null).
         expect(() =>
-          forkJoin(null).subscribe({
+          forkJoin(null as any).subscribe({
             // It sends the error to the subscription.
             error: () => done(),
           })

src/internal/observable/forkJoin.ts

@@ -1,12 +1,14 @@
 import { Observable } from '../Observable';
-import { ObservedValueOf, ObservableInputTuple } from '../types';
+import { ObservedValueOf, ObservableInputTuple, ObservableInput } from '../types';
 import { argsArgArrayOrObject } from '../util/argsArgArrayOrObject';
 import { innerFrom } from './from';
 import { popResultSelector } from '../util/args';
 import { OperatorSubscriber } from '../operators/OperatorSubscriber';
 import { mapOneOrManyArgs } from '../util/mapOneOrManyArgs';
 import { createObject } from '../util/createObject';
 
+export function forkJoin(scheduler: null | undefined): Observable<never>;
+
 // forkJoin([a, b, c])
 export function forkJoin(sources: readonly []): Observable<never>;
 export function forkJoin<A extends readonly unknown[]>(sources: readonly [...ObservableInputTuple<A>]): Observable<A>;
@@ -26,7 +28,9 @@ export function forkJoin<A extends readonly unknown[], R>(
 
 // forkJoin({a, b, c})
 export function forkJoin(sourcesObject: { [K in any]: never }): Observable<never>;
-export function forkJoin<T>(sourcesObject: T): Observable<{ [K in keyof T]: ObservedValueOf<T[K]> }>;
+export function forkJoin<T extends Record<string, ObservableInput<any>>>(
+  sourcesObject: T
+): Observable<{ [K in keyof T]: ObservedValueOf<T[K]> }>;
 
 /**
  * Accepts an `Array` of {@link ObservableInput} or a dictionary `Object` of {@link ObservableInput} and returns