Attributes on binder don't apply to a group

In this snippet
```fstar
let f ([@@@"attr"] x y : int) = 1
```
the attribute is only on `x`. This looks confusing to me, is it intended? One can add the attribute to both binders like this:
```fstar
let f ([@@@"attr"] x [@@@"attr"] y : int) = 1
```
