Make it easier to pass empty state st = (;)

[gdalle]

Hi there!
I am writing code with stateless neural networks, and I would like to be able to pass st = (;) (empty NamedTuple) everywhere instead of remembering the state from the Lux.setup funtion.
Judging by the code in layers/basic.jl, it should work with every layer... except Chain because of this line, where st is annotated as a NamedTuple{fields} instead of a NamedTuple. Is there a specific reason for this?

[avik-pal]

Actually, the other ones should be annotated with fields. Also I don't think it will do what you want. It still tries to access the fields of the named tuple, so for an empty namedtuple it should error.

[gdalle]

At least the PR passes the tests 🤷 Since that Chain was incoherent with the rest, I knew it was either all or nothing on the NamedTuple annotation. Just kinda sad it ends up being all instead of nothing 😉

[gdalle]

Do you want a PR that does the change in the reverse direction, and annotates all st arguments with NamedTuple{blabla}? I think that one would be breaking though

[avik-pal]

It's not breaking, apply* are not public API. Also in either case it would error, with stricter types IMO it is easier to debug.

At least the PR passes the tests

Its because the layers use the correct structure. The failure will only occur if we pass an incorrectly structured nt.

[lungd]

Speaking of tests, are the tests setup and working properly?
With that PR basic.jl#268 should have failed?
Or is it because of the CI settings. I mean, why did that PR pass

[avik-pal]

Speaking of tests, are the tests setup and working properly?

That's just an untested code path.

[gdalle]

OK, so let's close this? One day, I'll make a PR to Lux that gets accepted 💪