title: Cannot compile @Injectable in angular 6
body: <p>recently I upgraded to:</p>
  
  <ul>
  <li>angular-cli 6.0.7</li>
  <li>angular 6.0.3</li>
  </ul>
  
  <p>I have generated a new project and wanted to use the new Injectable decorator.
  When decorating a class:</p>
  
  <pre><code>  @Injectable({
        providedIn: 'root'
     })
     export class SomeService {
         constructor() { }
     }
  </code></pre>
  
  <p>I get following compile error:</p>
  
  <blockquote>
    <p>Argument type {providedIn: "root"} is not assignable to parameter
    type {providedIn: Type | "root" | null} &amp; InjectableProvider 
        Checks TypeScript called function parameters , return values , assigned expressions to be of correct type.</p>
  </blockquote>
  
  <p>When I write the class like:</p>
  
  <pre><code> @Injectable
   export class SomeService {
      constructor() { }
   }
  </code></pre>
  
  <p>I get a runtime error with the same message.</p>
  
  <p>Any ideas?</p>