With TypeScript 2.4.2 and rxjs 5.0.1,
Visual Studio Code shows following error for this.heroes = this.searchTerms line
of ngOnInit in hero-search.component.ts.
main error message is
The 'this' context of type 'Subject' is not assignable to method's 'this' of type 'Observable'.
Types of property 'lift' are incompatible.
...
With TypeScript 2.4.2 and rxjs 5.0.1, Visual Studio Code shows following error for
this.heroes = this.searchTermsline ofngOnInitinhero-search.component.ts.main error message is
Updating rxjs to 5.4.2 solves the problem. (https://github.com/ReactiveX/rxjs/issues/2539 for detail)