I'm not sure if this is the right way to go. I'm more inclined to use a library like https://docs.rs/non-empty-vec/latest/non_empty_vec/ to make sure the fields always have a value, and None == struct but 0 fields == enum but 0 fields

Can you come up with a use-case where a developer who is using virtue wants to differentiate between struct Foo;, struct Foo { } and struct Foo();?

Codecov Report

Patch coverage: 94.28% and project coverage change: +0.94 🎉

Comparison is base (eb18f25) 49.13% compared to head (930d8d6) 50.07%.

@@            Coverage Diff             @@
##            trunk      #49      +/-   ##
==========================================
+ Coverage   49.13%   50.07%   +0.94%     
==========================================
  Files          19       19              
  Lines        1911     1945      +34     
==========================================
+ Hits          939      974      +35     
+ Misses        972      971       -1     

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At the moment I'm using empty-brace syntax for my empty structs, like NewKeys below. No particular reason other than consistency with my non-empty structs (they're a set of packet formats).

#[derive(Debug, SSHEncode, SSHDecode)]
pub struct NewKeys {}

// alternative using a unit struct
#[derive(Debug, SSHEncode, SSHDecode)]
pub struct Ignore;

From what I can tell with the new Virtue there isn't a way to distinguish between these two cases in the parser. If I want to generate a constructor for them they need different syntax, Self {} vs Self. I could just change all of them to be unit structs, but it seems Virtue should be able to express either?

// generated code
impl<'de> crate::sshwire::SSHDecode<'de> for NewKeys {
    fn dec<S: crate::sshwire::SSHSource<'de>>(
        s: &mut S,
    ) -> crate::sshwire::WireResult<Self> {
        Ok(Self)
    }
}

52 | #[derive(Debug, SSHEncode, SSHDecode)]
   |                            ^^^^^^^^^ help: use curly brackets: `Self { /* fields */ }`

Oh, I only just realised the empty brace constructor is fine for any of unit/empty-struct/empty-tuple. So perhaps the current behaviour is fine to leave as-is, any None fields variant can use Self {}.

    struct A;
    struct B();
    struct C {};
    let a = A {};
    let b = B {};
    let c = C {};

Thinking about it more I think it's probably beneficial to determine between the delimiter even if there's no fields.

There is also an assert here that should be removed.

If you can remove that and fix the linting issues I think this is good to merge

It turns out .names() wasn't getting called at all in tests so I've added that too. Thanks!