nixf doesn't report unused @args with function arguments

[Aleksanaa]

Describe the bug

args in { foo, bar }@args isn't reported to be unused.

Logs (Required)

Configuration

If you have some custom configuration, please paste it here.

To Reproduce
Create a new Nix file and type this:

{ foo, bar }@args:

foo + bar

args is unused. nixd doesn't report this, also neither does nixf:

=> nixf-tidy < a.nix 
[]

Expected behavior
Report a warning on args being unused.

Screenshots

Additional context
Found in #558