How to return Observable<T> from Promise?

I am trying to return an authResult from the following method but it looks like all execution paths do not return a value.

Here's my method:

public loginWithFacebook(): Observable<AuthResult> {
this.fbService.login().then((authResponse: any) => {
const accessToken = authResponse.accessToken;
return this.model.loginWithFacebook(accessToken).pipe(tap(res => this.setSession(res)), shareReplay());

});
}


here's the error message:

A function whose declared type is neither 'undefined', 'void', nor 'any' must return a value.

How can I rewrite this to return Observable?

Thanks for any attention.

Continue reading...