[ide] hover over struct field name in type parameter not working

```haxe
typedef Response = {}

typedef ErrorResponse = Response<{
var error:String;
}>;
```

When hovering over the field name, you just get the entire range instead of a hover for the field:


Hovering over the `:String` type hint works fine. Isolated from vscode-debugadapter-extern, where a lot of types are defined like this.