title: Typescript noImplicitAny and noImplicitReturns not working as expected
body: <p>I have added the "noImplicitAny" and "noImplicitReturns" to my Typescript tsconfig.json file:</p>
  
  <pre><code>{
      "compilerOptions": {
          "target":"es5",
          "noImplicitAny": true,
          "noImplicitThis": true,
          "noImplicitReturns": true,
          "noUnusedLocals":true,
          "out": "dist/js/main.js"
      }
  }
  </code></pre>
  
  <p>I expected that the following code would generate errors, or at least warnings:</p>
  
  <pre><code>private randomMove() {  // no return type but no warning :(
      let o = 3;          // no type for o but no warning :(
  }
  </code></pre>
  
  <p>The "noUnusedLocals" IS working.</p>
  
  <p>Is this how it's supposed to work, am I missing something?
  Is it possible to have Visual Studio Code generate warnings when you don't specify types / return types?</p>