Typescript eats Google Closure type cast comment

**TypeScript Version:**  2.4.20

**Code**

```ts
function f() {
    return /* @type {number} */ 42;
}
```

**Expected behavior:**
Should be compiled to
```js
function f() {
    return /* @type {number} */ 42;
}
```

**Actual behavior:**
Compiled to
```js
function f() {
    return 42;
}
```
