Info missing when hover on a proptery compare to TS6

### Acknowledgement

- [x] I acknowledge that issues using this template may be closed without further explanation at the maintainer's discretion.

### Comment

## Platform

vscode

## code

```ts
declare const x: { [k: string]: number }

x./*1*/a
```

Hover on `a` of `x.a`.

## TS6

```
(index) x[string]: number
```

## TS7

```
number
```

notice that **ts7 only shows `number` here.**