Fix stateQueue typing

src/renderers/shared/fiber/ReactFiber.js

@@ -78,7 +78,7 @@ export type Fiber = Instance & {
   // TODO: I think that there is a way to merge pendingProps and memoizedProps.
   memoizedProps: any, // The props used to create the output.
   // A queue of local state updates.
-  stateQueue: StateQueue,
+  stateQueue: ?StateQueue,
   // The state used to create the output. This is a full state object.
   memoizedState: any,
   // Output is the return value of this fiber, or a linked list of return values

src/renderers/shared/fiber/ReactFiberBeginWork.js

@@ -152,7 +152,9 @@ module.exports = function<T, P, I, C>(config : HostConfig<T, P, I, C>, getSchedu
   const updater = {
     enqueueSetState(instance, partialState) {
       const fiber = instance._fiber;
-      const stateQueue = addToQueue(fiber.stateQueue, partialState);
+      const stateQueue = fiber.stateQueue ?
+        addToQueue(fiber.stateQueue, partialState) :
+        createStateQueue(partialState);
       scheduleUpdate(fiber, stateQueue, LowPriority);
     },
   };
@@ -181,7 +183,9 @@ module.exports = function<T, P, I, C>(config : HostConfig<T, P, I, C>, getSchedu
       state = instance.state || null;
       // The initial state must be added to the pending state queue in case
       // setState is called before the initial render.
-      workInProgress.stateQueue = createStateQueue(state);
+      if (state !== null) {
+        workInProgress.stateQueue = createStateQueue(state);
+      }
       // The instance needs access to the fiber so that it can schedule updates
       instance._fiber = workInProgress;
       instance.updater = updater;

src/renderers/shared/fiber/ReactFiberStateQueue.js

@@ -14,9 +14,9 @@
 
 export type StateQueue = {
   partialState: any,
-  next: StateQueue,
-  tail: StateQueue
-} | null;
+  next: StateQueue | null,
+  tail: StateQueue | null
+};
 
 exports.createStateQueue = function(partialState : mixed) : StateQueue {
   return {
@@ -28,9 +28,6 @@ exports.createStateQueue = function(partialState : mixed) : StateQueue {
 
 exports.addToQueue = function(queue : StateQueue, partialState : mixed): StateQueue {
   const node = exports.createStateQueue(partialState);
-  if (queue === null) {
-    return node;
-  }
   if (queue.tail === null) {
     queue.next = node;
   } else {
@@ -40,8 +37,8 @@ exports.addToQueue = function(queue : StateQueue, partialState : mixed): StateQu
   return queue;
 };
 
-exports.mergeStateQueue = function(prevState : any, props : any, queue : StateQueue) : any {
-  if (queue === null) {
+exports.mergeStateQueue = function(prevState : any, props : any, queue : ?StateQueue) : any {
+  if (!queue) {
     return prevState;
   }
   let state = Object.assign({}, prevState);