Attribute Macro lifecycle 

#[lifecycle]

Turn a plain state enum into a statically-verified lifecycle.

Applied to an enum with an initial state, one or more terminal states, and a set of transitions, this preserves the original enum and appends metadata consts (LIFECYCLE_INITIAL, LIFECYCLE_TERMINALS, LIFECYCLE_STATES, LIFECYCLE_TRANSITIONS) plus can_transition_to on the enum, and a typestate transition module (named after the enum in snake_case) whose Machine<S> only exposes to_<target> methods for declared edges — firing an undeclared transition is a compile error.

Examples

use autumn_web::lifecycle;

#[lifecycle(
    initial = Draft,
    terminal(Archived),
    transitions(
        Draft -> Published,
        Published -> Archived,
        Published -> Draft,
    )
)]
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum ArticleState { Draft, Published, Archived }

Turn a plain state enum into a statically-verified lifecycle.

Given a declared initial state, one or more terminal states, and a set of transitions, #[lifecycle] preserves the original enum and appends:

1. Metadata consts (LIFECYCLE_INITIAL, LIFECYCLE_TERMINALS, LIFECYCLE_STATES, LIFECYCLE_TRANSITIONS) and a can_transition_to runtime check on the enum. Because these reference the enum’s own variants, a declared state that is not a real variant is a compile error.
2. A typestate transition module named after the enum in snake_case, whose Machine<S> exposes a consuming to_<target> method only for declared edges — firing an undeclared transition does not compile.

Example

use autumn_web::lifecycle;

#[lifecycle(
    initial = Draft,
    terminal(Archived),
    transitions(
        Draft -> Published,
        Published -> Archived,
        Published -> Draft,
    )
)]
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum ArticleState { Draft, Published, Archived }

let m = article_state::Machine::<article_state::Draft>::start();
let m = m.to_published();      // only declared edges exist as methods
assert_eq!(m.current(), ArticleState::Published);
assert!(ArticleState::Draft.can_transition_to(&ArticleState::Published));