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Remove unsafe type assertions in StateMachine #840

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Remove unsafe type assertions in StateMachine #840

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10 changes: 4 additions & 6 deletions lib/StateMachine.ts
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Original file line number Diff line number Diff line change
@@ -1,5 +1,3 @@
import type {ReadonlyDeep} from 'type-fest';

/**
* A directed transition graph keyed by state name.
* Use `as const` when defining a graph so illegal transitions are caught at compile time.
Expand Down Expand Up @@ -34,13 +32,13 @@ type TransitionsFrom<Graph extends TransitionGraph, Current extends keyof Graph
* loadingMachine.transition('success');
*/
class StateMachine<const Graph extends TransitionGraph, Current extends keyof Graph & string> {
/** The current state. Deeply readonly and owned by this state machine instance. */
readonly state: ReadonlyDeep<Current>;
/** The current state. Owned by this state machine instance. */
readonly state: Current;

private readonly transitions: Graph;

constructor(currentState: Current, transitions: Graph) {
this.state = currentState as ReadonlyDeep<Current>;
this.state = currentState;
this.transitions = transitions;
Object.freeze(this);
}
Expand All @@ -50,7 +48,7 @@ class StateMachine<const Graph extends TransitionGraph, Current extends keyof Gr
* Only transitions declared in the graph for the current state are accepted.
*/
transition<Target extends TransitionsFrom<Graph, Current>>(target: Target): StateMachine<Graph, Target> {
const validTargets = this.transitions[this.state as Current];
const validTargets = this.transitions[this.state];
if (!validTargets?.includes(target)) {
throw new Error(`Illegal transition from "${String(this.state)}" to "${String(target)}"`);
}
Expand Down
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