Function enqueueUpdate

packages/react-reconciler/src/updateQueue.ts:45–68

(
	updateQueue: UpdateQueue<State>,
	update: Update<State>,
	fiber: FiberNode,
	lane: Lane
)

};

export const enqueueUpdate = <State>(
	updateQueue: UpdateQueue<State>,
	update: Update<State>,
	fiber: FiberNode,
	lane: Lane
) => {
	const pending = updateQueue.shared.pending;
	if (pending === null) {
		// pending = a -> a
		update.next = update;
	} else {
		// pending = b -> a -> b
		// pending = c -> a -> b -> c
		update.next = pending.next;
		pending.next = update;
	}
	updateQueue.shared.pending = update;

	fiber.lanes = mergeLanes(fiber.lanes, lane);
	const alternate = fiber.alternate;
	if (alternate !== null) {
		alternate.lanes = mergeLanes(alternate.lanes, lane);
	}
};

export function basicStateReducer<State>(
	state: State,