qubit_state_machine/standard/
state_machine_build_error.rs

1/*******************************************************************************
2 *
3 *    Copyright (c) 2026 Haixing Hu.
4 *
5 *    SPDX-License-Identifier: Apache-2.0
6 *
7 *    Licensed under the Apache License, Version 2.0.
8 *
9 ******************************************************************************/
10//! Validation errors returned when building a state machine.
11
12use std::fmt::Debug;
13
14use thiserror::Error;
15
16/// Error returned when state machine rules are internally inconsistent.
17///
18/// `S` is the state type and `E` is the event type.
19#[derive(Debug, Clone, Copy, Eq, PartialEq, Error)]
20pub enum StateMachineBuildError<S, E>
21where
22    S: Debug,
23    E: Debug,
24{
25    /// An initial state was configured but not registered as a state.
26    #[error("initial state is not registered: {state:?}")]
27    InitialStateNotRegistered {
28        /// The unregistered initial state.
29        state: S,
30    },
31    /// A final state was configured but not registered as a state.
32    #[error("final state is not registered: {state:?}")]
33    FinalStateNotRegistered {
34        /// The unregistered final state.
35        state: S,
36    },
37    /// A transition source was not registered as a state.
38    #[error("transition source is not registered: {source_state:?} --{event:?}--> {target:?}")]
39    TransitionSourceNotRegistered {
40        /// Source state of the invalid transition.
41        source_state: S,
42        /// Event of the invalid transition.
43        event: E,
44        /// Target state of the invalid transition.
45        target: S,
46    },
47    /// A transition target was not registered as a state.
48    #[error("transition target is not registered: {source_state:?} --{event:?}--> {target:?}")]
49    TransitionTargetNotRegistered {
50        /// Source state of the invalid transition.
51        source_state: S,
52        /// Event of the invalid transition.
53        event: E,
54        /// Target state of the invalid transition.
55        target: S,
56    },
57    /// Two transitions use the same `(source, event)` with different targets.
58    #[error(
59        "duplicate transition target: {source_state:?} --{event:?}--> \
60         {existing_target:?} conflicts with {new_target:?}"
61    )]
62    DuplicateTransition {
63        /// Source state shared by both transitions.
64        source_state: S,
65        /// Event shared by both transitions.
66        event: E,
67        /// Target registered first.
68        existing_target: S,
69        /// Conflicting target registered later.
70        new_target: S,
71    },
72}
qubit_state_machine/standard/state_machine_build_error.rs

qubit_state_machine/standard/
state_machine_build_error.rs
