Stricter type definition of Subject

spec/Subject-spec.ts

@@ -271,7 +271,7 @@ describe('Subject', () => {
   });
 
   it('should not allow values to be nexted after it is unsubscribed', (done: MochaDone) => {
-    const subject = new Subject();
+    const subject = new Subject<string>();
     const expected = ['foo'];
 
     subject.subscribe(function (x) {
@@ -397,7 +397,7 @@ describe('Subject', () => {
 
   it('should be an Observer which can be given to Observable.subscribe', (done: MochaDone) => {
     const source = of(1, 2, 3, 4, 5);
-    const subject = new Subject();
+    const subject = new Subject<number>();
     const expected = [1, 2, 3, 4, 5];
 
     subject.subscribe(
@@ -414,7 +414,7 @@ describe('Subject', () => {
 
   it('should be usable as an Observer of a finite delayed Observable', (done: MochaDone) => {
     const source = of(1, 2, 3).pipe(delay(50));
-    const subject = new Subject();
+    const subject = new Subject<number>();
 
     const expected = [1, 2, 3];
 
@@ -431,7 +431,7 @@ describe('Subject', () => {
   });
 
   it('should throw ObjectUnsubscribedError when emit after unsubscribed', () => {
-    const subject = new Subject();
+    const subject = new Subject<string>();
     subject.unsubscribe();
 
     expect(() => {

spec/observables/from-spec.ts

@@ -139,8 +139,8 @@ describe('from', () => {
       expect(nextInvoked).to.equal(false);
     });
     it(`should accept a function`, (done) => {
-      const subject = new Subject();
-      const handler: any = (...args: any[]) => subject.next(...args);
+      const subject = new Subject<any>();
+      const handler: any = (arg: any) => subject.next(arg);
       handler[observable] = () => subject;
       let nextInvoked = false;
 

spec/operators/bufferCount-spec.ts

@@ -45,7 +45,7 @@ describe('bufferCount operator', () => {
   });
 
   it('should buffer properly (issue #2062)', () => {
-    const item$ = new Subject();
+    const item$ = new Subject<number>();
     const results: any[] = [];
     item$.pipe(
       bufferCount(3, 1)

spec/operators/skipUntil-spec.ts

@@ -247,7 +247,7 @@ describe('skipUntil', () => {
     const e1 =   hot( '--a--b--c--d--e--|');
     const e1subs =   ['^                !',
                       '^                !']; // for the explicit subscribe some lines below
-    const skip = new Subject();
+    const skip = new Subject<string>();
     const expected =  '-----------------|';
 
     e1.subscribe((x: string) => {

src/internal/Subject.ts

@@ -25,7 +25,7 @@ export class SubjectSubscriber<T> extends Subscriber<T> {
  *
  * @class Subject<T>
  */
-export class Subject<T> extends Observable<T> implements SubscriptionLike {
+export class Subject<T = void> extends Observable<T> implements SubscriptionLike {
 
   [rxSubscriberSymbol]() {
     return new SubjectSubscriber(this);
@@ -58,7 +58,7 @@ export class Subject<T> extends Observable<T> implements SubscriptionLike {
     return <any>subject;
   }
 
-  next(value?: T) {
+  next(value: T) {
     if (this.closed) {
       throw new ObjectUnsubscribedError();
     }

src/internal/operators/repeatWhen.ts

@@ -60,7 +60,7 @@ class RepeatWhenOperator<T> implements Operator<T, T> {
  */
 class RepeatWhenSubscriber<T, R> extends OuterSubscriber<T, R> {
 
-  private notifications: Subject<any> | null = null;
+  private notifications: Subject<void> | null = null;
   private retries: Observable<any> | null = null;
   private retriesSubscription: Subscription | null | undefined = null;
   private sourceIsBeingSubscribedTo: boolean = true;

src/internal/operators/share.ts

@@ -6,7 +6,7 @@ import { Subject } from '../Subject';
 import { MonoTypeOperatorFunction } from '../types';
 
 function shareSubjectFactory() {
-  return new Subject();
+  return new Subject<any>();
 }
 
 /**

src/internal/operators/windowTime.ts

@@ -165,7 +165,7 @@ interface CloseState<T> {
 class CountedSubject<T> extends Subject<T> {
   private _numberOfNextedValues: number = 0;
 
-  next(value?: T): void {
+  next(value: T): void {
     this._numberOfNextedValues++;
     super.next(value);
   }