[Bug] 'Pattern as' capture errors

[bashful-strix]

Sorry for the bunch of issues in one go...
The 'pattern as' capture seems be unhappy; I suspect it's interpreting it as visible type application instead.

With:

Without:

I had a quick look through the recent changes (since this used to work) and the only thing that looked likely was @ becoming external. I don't know enough about writing actual treesitter grammars to know if that's right or make a fix though.