Generic type inferred as supertype if that's the callback parameter type

**TypeScript Version:**  nightly (2.2.0-dev.20161214)

(Ref: https://github.com/Microsoft/TypeScript/pull/12862#discussion_r92284049)

**Code**

```ts
function f<T>(x: T[], y: (t: T) => void): T[] { return x; }
function g(value: {}): void {}
const x: number[] = f([1, 2], g);
```

**Expected behavior:**

Infers `f<number>`.

**Actual behavior:**

Infers `f<{}>`.