export interface TestInterface {
  propertyExists: boolean;
}

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent {
  test: TestInterface;
  constructor() {
    this.test = {
      propertyExists: true
    };
  }
}

<p>
  Property exists: {{ test.propertyExists }}
</p>
<p *ngIf="true">
  Property does not exist: {{ test.propertyDoesNotExist }}
</p>

<p>
Property does not exist: {{ test.propertyDoesNotExist }}
</p>

ERROR in srcappapp.component.html(5,7): : Property 'propertyDoesNotExist'
does not exist on type 'TestInterface'.

Identifier 'propertyDoesNotExist' is not defined. 'TestInterface' does not
contain such a member(undefined)