JSDoc `Function` quickInfo shows `{}`

**TypeScript Version:**   nightly (2.4.0-dev.20170513)

**Code**

```ts
// @ts-check
/** @type {Function} */
const x = (a) => a + 1;
x(1);
```

**Expected behavior:**

Quick-info for `x` should show `Function`.

**Actual behavior:**

Quick-info for `x` shows `{}`.
But the program does not compile if I use `@type {{}}`, 