title: String Enum in typescript error
body: <p>I tried to add a string enum to my Angular 2 project, but error occur during starting of project with npm:</p>
  
  <pre><code>ERROR in e:/projects/dbtool-fullstack/dbtool-client/src/app/shared/models/full-m
  odels/enums/Sex.ts (2,10): Type '"Male"' is not assignable to type 'Sex'.
  ERROR in e:/projects/dbtool-fullstack/dbtool-client/src/app/shared/models/full-m
  odels/enums/Sex.ts (3,12): Type '"Female"' is not assignable to type 'Sex'.
  ERROR in e:/projects/dbtool-fullstack/dbtool-client/src/app/shared/models/full-m
  odels/enums/Sex.ts (4,8): Type '"NA"' is not assignable to type 'Sex'. 
  </code></pre>
  
  <p>The Enum declaration:</p>
  
  <pre><code>export enum Sex {
    Male = 'Male',
    Female = 'Female',
    NA = 'NA'
  }
  </code></pre>
  
  <p>And typescript version:</p>
  
  <pre><code>e:\projects\dbtool-fullstack\dbtool-client&gt;tsc --version
  Version 2.5.3
  
  e:\projects\dbtool-fullstack\dbtool-client&gt;npm list -g --depth=0
  C:\Users\pavlo\AppData\Roaming\npm
  +-- @angular/cli@1.4.4
  +-- npm@5.5.1
  `-- typescript@2.5.3
  </code></pre>
  
  <p>This type of Enum declaration should work starting from version 2.4.0</p>
  
  <p>What could cause this?</p>
  
  <p><strong>UPDATE</strong></p>
  
  <p>When i use ng -v:</p>
  
  <pre><code>e:\projects\TESTENUMS&gt;ng -v
      _                      _                 ____ _     ___
     / \   _ __   __ _ _   _| | __ _ _ __     / ___| |   |_ _|
    / △ \ | '_ \ / _` | | | | |/ _` | '__|   | |   | |    | |
   / ___ \| | | | (_| | |_| | | (_| | |      | |___| |___ | |
  /_/   \_\_| |_|\__, |\__,_|_|\__,_|_|       \____|_____|___|
                 |___/
  @angular/cli: 1.4.9
  node: 6.11.3
  os: win32 ia32
  @angular/animations: 4.4.6
  @angular/common: 4.4.6
  @angular/compiler: 4.4.6
  @angular/core: 4.4.6
  @angular/forms: 4.4.6
  @angular/http: 4.4.6
  @angular/platform-browser: 4.4.6
  @angular/platform-browser-dynamic: 4.4.6
  @angular/router: 4.4.6
  @angular/cli: 1.4.9
  @angular/compiler-cli: 4.4.6
  @angular/language-service: 4.4.6
  typescript: 2.3.4
  </code></pre>
  
  <p>the version of TS is 2.3.4 in this case. I don't know where does it come from though.</p>