title: What happened with subscription if subject was destroyed in angular 2+?
body: <p><strong>UPDATE more details about observable usage</strong></p>
  
  <p><em>I've need service because checkboxcell component can't use @Output() property.</em>
  This happened becaues of wrong usage with ag-grid api - renderer component was used as editor. It can't be corrected at this moment.</p>
  
  <pre><code>@Component({
      ...
      template: `&lt;mat-checkbox (change)="onChanged($event)"&gt;&lt;/mat-checkbox&gt;`
  })
  export class CheckboxCellComponent implements ICellRendererAngularComp {
      ...
      //each component that use checkboxcell provide own instance of PermissionChange
      constructor(private permissionChange: PermissionChange) {
  
      }
      public onChanged({ checked }): void {
           //use observable
           this.permissionChange.changeEvent.next();
      }
  }
  </code></pre>
  
  <p><strong>ORIGINAL question</strong></p>
  
  <p>I have a simple service</p>
  
  <pre><code>export class PermissionChange {
      public changeEvent: Subject&lt;void&gt;;
      constructor() {
          this.changeEvent = new Subject&lt;void&gt;();
      }
  }
  </code></pre>
  
  <p>And component, that use the service:</p>
  
  <pre><code>@Component({
      ...
      providers: [PermissionChange]
  })
  export class ...Component implements OnInit {
      constructor(
          private permissionChange: PermissionChange,
      ) { }
  
      public ngOnInit(): void {
          //subscription
          this.permissionChange.changeEvent.subscribe(() =&gt; {...});
      }
  }
  </code></pre>
  
  <p><code>PermisionChange</code> is personal provider for this component => instance of <code>PermisionChange</code> will be destroyed in the moment when component will be destroyed => <code>changeEvent</code> observable will be destroyed too. So maybe there is no need to unsubscribe, maybe subscribtion will be destroyed too? But I don't know how to check it.</p>