No way to type an object with null prototype

まだ誰も着手していません。

Currently the base type of all objects in TS seems to be `{}`, which looks like an empty type but actually has members inherited from the Object object. This leaves no way to express a type with null prototype.

``` javascript
var foo: ??? = Object.create(null);
foo.toString(); // Want a compile error here
```

I did accidentally discover that it's possible to type a variable as void:

``` javascript
var foo: void = Object.create(null);
```

This appears to suppress intellisense for members in VS and the playground, and it is assignable to `any` (`Object.keys(foo)` compiles), so it would seem to be what I'm looking for. However this still lets `foo.toString()` compile somehow - I imagine the void type is getting elevated to Object automatically.

Edit: [Ryan's workaround](https://github.com/Microsoft/TypeScript/issues/1108#issuecomment-62406685) to subtype Object and override all its members to void prevents those properties from being called as functions, but as he points out, that doesn't prevent them from being accessed.

``` javascript
var bar = foo.toString; // Want a compiler error here too. Won't get one with Ryan's workaround.
```

TypeScript playground で Object.create(null) の例を再現し、その後、{}, void、Object のメンバーがどのようにモデル化されているかを追跡します。対応する型が null プロトタイプのオブジェクトを表現でき、メンバーアクセスの両方の例を拒否できれば完了です。この issue では対象とするファイルやテストは指定されていません。

索引モデルが issue の本文から書いたものです。