title: Type is not assignable to type providedIn Property ProvidedIn is missing
body: <p>I am trying to create a service with the help of Angular's tutorial <a href="https://angular.io/guide/http" rel="nofollow noreferrer">https://angular.io/guide/http</a></p>
  
  <p>I'm using Angular <code>7.0.7</code>.</p>
  
  <p>The service would get json data from some url:</p>
  
  <pre><code>import { Injectable } from '@angular/core';
  import { HttpClient } from '@angular/common/http';
  
  @Injectable
  export class ProductListService {
    constructor(private http: HttpClient) {
    }
  
    productListUrl: string = "https://blahblah.com/products";
  
    getProductList() {
      return this.http.get(this.productListUrl);
    }
  }
  </code></pre>
  
  <p>I am getting a squiggly line under <code>@Injectable()</code> with the title of this question. Why is that happening, and how do I resolve it?</p>
  
  <p>I have a component which will be using this service:</p>
  
  <pre><code> import { ProductListService } from '../services/productList.service';
   @Component({
     selector: 'app-productlist',
     templateUrl: './productlist.component.html',
     styleUrls: ['./productlist.component.css'],
     providers: [ProductListService]
   })
  </code></pre>