Error: Type Observable is not assignable to type Observable

Type 'Observable<unknown>' is not assignable to type 'Observable<UserInfo>'. Type '{}' is missing the following properties from type 'UserInfo': displayName, email, phoneNumber, photoURL, and 2 more.

 get AppUser$(): Observable<firebase.default.UserInfo> {
    return this.authSvr.user$.pipe(
      switchMap((user) => {
          if(user){
              return this.getUser(user.uid).valueChanges()
            } else {
                  return Observable.of(null)
            }
        })
    );
}