[Feature Request] Allow pre-declaring the `enumerate` type's output for Derive usage

[Dessix]

It would be helpful if the enum produced by typestate(enumerate = ...) could be pre-declared such that #[derive(...)] can be used upon it or potentially (a subset of?) its members.

#[typestate(enumerate = "StateMachineStates")
pub mod state_machine {
  #[automaton]
  #[derive(Debug, Clone, PartialEq, Eq)]
  pub struct StateMachine;

  #[state] pub struct In;
  #[state] pub struct Out;

  // No field-specific annotations
  #[enumerate]
  #[derive(Debug, Clone, PartialEq, Eq)]
  pub enum StateMachineStates;

  // or, with fields annotated for another annotation-macro
  #[enumerate]
  #[derive(derivative)]
  #[derivative(Debug)]
  pub enum StateMachineStates {
    #[derivative(Debug="transparent")]
    In,
    // Note that only some states are included
    // Any not explicitly mentioned are filled in prior to other #[derive]s expanding.
  }

  // ...
}

[jmg-duarte]

Hey @Dessix! Thank you for your interest!

This crate has been in a weird state since this was my MSc's thesis PoC and I haven't had time since to work on it. Only recently I have started to think about ways to make it simpler both the DSL and the macro powering it.

That said, I can't make any promises. If you have any more ideas or suggestions, feel free to share them in the discussions or issues!

[Dessix]

Thanks! I'm hoping to make use of this for its self-documenting features to more-strictly encode various protocols in one of my projects, and have been mulling over a helper annotation for creating the trait impls without all of the verbosity and boilerplate. Ideally, the proc-macro annotation would handle this so it could utilize the contextual information from the main mod body.

I think one of the big parts of making an effective DSL is keeping it from getting in the way of the language's features- the relevant one here being derive. Feel free to bounce ideas off of me if you're not sure of a particular syntactical direction to take, or how to implement some aspect of the macro processing.