Unclosed object binding patterns do not give correct completions

Now that #3615 is in, here's an annoying one for editors without brace completion:

``` TypeScript
interface Thing {
    abcdef: any;
}

interface I {
    property1: Thing;
    property2: string;
}
var foo: I;
var { property1: { /**/ } = foo;
```

Expected: `abcdef` is in the completion list.
Actual: `property1` and `property2` are in the completion list.
