I’m getting an error: Function lacks ending return statement and return type does not include ‘undefined’.

import { HttpInterceptor, HttpRequest, HttpHandler, HttpUserEvent, HttpEvent } from "@angular/common/http";
import { Observable } from "rxjs";
import { LoginService } from "../services/login.service";
import 'rxjs/add/operator/do';
import { Injectable } from "@angular/core";
import { Router } from "@angular/router";

@Injectable()
export class AuthInterceptor implements HttpInterceptor {

    constructor(private router: Router) { }

    intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> { // here error

        if (req.headers.get('No-Auth') == "True")
            return next.handle(req.clone());

        if (localStorage.getItem('userToken') != null) {
            const clonedreq = req.clone({
                headers: req.headers.set("Authorization", "Bearer " + localStorage.getItem('userToken'))
            });
            return next.handle(clonedreq)
                .do(
                succ => { },
                err => {
                    if (err.status === 401)
                        this.router.navigateByUrl('/signin');
                }
                );
        }
        else {
            this.router.navigateByUrl('/sigin');
        }
    }
}

I’ve tried do it with try but I’m still getting the same error.

Does anyone knows how to make it work?

Source: Angular Questions