`--noUnusedLocals` does not work at top-level of commonJS module

**TypeScript Version:**  nightly (2.5.0-dev.20170712)

**Code**

```ts
const a = 1;
const b = 2;
{
	const c = 3;
}

module.exports = { a };
```

**Expected behavior:**

Errors for both `b` and `c`.

**Actual behavior:**

Only error for `c`.