facebook · kassens · Aug 22, 2025 · Aug 20, 2025
diff --git a/package.json b/package.json
@@ -74,8 +74,8 @@
     "eslint-plugin-react-internal": "link:./scripts/eslint-rules",
     "fbjs-scripts": "^3.0.1",
     "filesize": "^6.0.1",
-    "flow-bin": "^0.266",
-    "flow-remove-types": "^2.266",
+    "flow-bin": "^0.267",
+    "flow-remove-types": "^2.267",
     "flow-typed": "^4.1.1",
     "glob": "^7.1.6",
     "glob-stream": "^6.1.0",

diff --git a/packages/react-devtools-shared/src/backend/fiber/renderer.js b/packages/react-devtools-shared/src/backend/fiber/renderer.js
@@ -1317,9 +1317,9 @@ export function attach(
     if (componentLogsEntry === undefined) {
       componentLogsEntry = {
         errors: new Map(),
-        errorsCount: 0,
+        errorsCount: 0 as number,
         warnings: new Map(),
-        warningsCount: 0,
+        warningsCount: 0 as number,
       };
       fiberToComponentLogsMap.set(fiber, componentLogsEntry);
     }

diff --git a/packages/react-devtools-shared/src/backend/flight/renderer.js b/packages/react-devtools-shared/src/backend/flight/renderer.js
@@ -118,9 +118,9 @@ export function attach(
     if (componentLogsEntry === undefined) {
       componentLogsEntry = {
         errors: new Map(),
-        errorsCount: 0,
+        errorsCount: 0 as number,
         warnings: new Map(),
-        warningsCount: 0,
+        warningsCount: 0 as number,
       };
       componentInfoToComponentLogsMap.set(componentInfo, componentLogsEntry);
     }

diff --git a/packages/react-reconciler/src/ReactFiberApplyGesture.js b/packages/react-reconciler/src/ReactFiberApplyGesture.js
@@ -488,7 +488,7 @@ function recursivelyInsertNewFiber(
       const viewTransitionState: ViewTransitionState = finishedWork.stateNode;
       // TODO: If this was already cloned by a previous pass we can reuse those clones.
       viewTransitionState.clones = null;
-      let nextPhase;
+      let nextPhase: VisitPhase;
       if (visitPhase === INSERT_EXIT) {
         // This was an Enter of a ViewTransition. We now move onto inserting the inner
         // HostComponents and finding inner pairs.
@@ -637,7 +637,7 @@ function recursivelyInsertClonesFromExistingTree(
         // So we need it to be cleared before we do that.
         // TODO: Use some other temporary state to track this.
         child.flags &= ~Update;
-        let nextPhase;
+        let nextPhase: VisitPhase;
         if (visitPhase === CLONE_EXIT) {
           // This was an Enter of a ViewTransition. We now move onto unhiding the inner
           // HostComponents and finding inner pairs.
@@ -894,7 +894,7 @@ function insertDestinationClonesOfFiber(
         // Only insert clones if this tree is going to be visible. No need to
         // clone invisible content.
         // TODO: If this is visible but detached it should still be cloned.
-        let nextPhase;
+        let nextPhase: VisitPhase;
         if (visitPhase === CLONE_UPDATE && (flags & Visibility) !== NoFlags) {
           // This is the root of an appear. We need to trigger Enter transitions.
           nextPhase = CLONE_EXIT;
@@ -922,7 +922,7 @@ function insertDestinationClonesOfFiber(
       const viewTransitionState: ViewTransitionState = finishedWork.stateNode;
       // TODO: If this was already cloned by a previous pass we can reuse those clones.
       viewTransitionState.clones = null;
-      let nextPhase;
+      let nextPhase: VisitPhase;
       if (visitPhase === CLONE_EXIT) {
         // This was an Enter of a ViewTransition. We now move onto unhiding the inner
         // HostComponents and finding inner pairs.

diff --git a/packages/react-reconciler/src/ReactFiberCacheComponent.js b/packages/react-reconciler/src/ReactFiberCacheComponent.js
@@ -25,7 +25,7 @@ const AbortControllerLocal: typeof AbortController =
       function AbortControllerShim() {
         const listeners = [];
         const signal = (this.signal = {
-          aborted: false,
+          aborted: false as boolean,
           addEventListener: (type, listener) => {
             listeners.push(listener);
           },

diff --git a/packages/react-reconciler/src/ReactFiberHooks.js b/packages/react-reconciler/src/ReactFiberHooks.js
@@ -1208,7 +1208,7 @@ function useMemoCache(size: number): Array<mixed> {
               ? currentMemoCache.data
               : // Clone the memo cache before each render (copy-on-write)
                 currentMemoCache.data.map(array => array.slice()),
-            index: 0,
+            index: 0 as number,
           };
         }
       }
@@ -1218,7 +1218,7 @@ function useMemoCache(size: number): Array<mixed> {
   if (memoCache == null) {
     memoCache = {
       data: [],
-      index: 0,
+      index: 0 as number,
     };
   }
   if (updateQueue === null) {

diff --git a/packages/react-reconciler/src/ReactFiberWorkLoop.js b/packages/react-reconciler/src/ReactFiberWorkLoop.js
@@ -1060,7 +1060,7 @@ export function performWorkOnRoot(
     // even for regular pings.
     checkIfRootIsPrerendering(root, lanes);
 
-  let exitStatus = shouldTimeSlice
+  let exitStatus: RootExitStatus = shouldTimeSlice
     ? renderRootConcurrent(root, lanes)
     : renderRootSync(root, lanes, true);
 
@@ -1212,7 +1212,7 @@ function recoverFromConcurrentError(
   root: FiberRoot,
   originallyAttemptedLanes: Lanes,
   errorRetryLanes: Lanes,
-) {
+): RootExitStatus {
   // If an error occurred during hydration, discard server response and fall
   // back to client side render.
 
@@ -2520,7 +2520,7 @@ function workLoopSync() {
   }
 }
 
-function renderRootConcurrent(root: FiberRoot, lanes: Lanes) {
+function renderRootConcurrent(root: FiberRoot, lanes: Lanes): RootExitStatus {
   const prevExecutionContext = executionContext;
   executionContext |= RenderContext;
   const prevDispatcher = pushDispatcher(root.containerInfo);

diff --git a/packages/react-server/src/ReactFlightReplyServer.js b/packages/react-server/src/ReactFlightReplyServer.js
@@ -556,7 +556,7 @@ function createModelResolver<T>(
     }
   } else {
     blocked = initializingChunkBlockedModel = {
-      deps: cyclic ? 0 : 1,
+      deps: (cyclic ? 0 : 1) as number,
       value: (null: any),
     };
   }

diff --git a/packages/scheduler/src/forks/Scheduler.js b/packages/scheduler/src/forks/Scheduler.js
@@ -283,7 +283,7 @@ function unstable_runWithPriority<T>(
 }
 
 function unstable_next<T>(eventHandler: () => T): T {
-  var priorityLevel;
+  var priorityLevel: PriorityLevel;
   switch (currentPriorityLevel) {
     case ImmediatePriority:
     case UserBlockingPriority:

diff --git a/packages/scheduler/src/forks/SchedulerMock.js b/packages/scheduler/src/forks/SchedulerMock.js
@@ -286,7 +286,7 @@ function unstable_runWithPriority<T>(
 }
 
 function unstable_next<T>(eventHandler: () => T): T {
-  var priorityLevel;
+  var priorityLevel: PriorityLevel;
   switch (currentPriorityLevel) {
     case ImmediatePriority:
     case UserBlockingPriority:

diff --git a/packages/scheduler/src/forks/SchedulerPostTask.js b/packages/scheduler/src/forks/SchedulerPostTask.js
@@ -196,7 +196,7 @@ export function unstable_getCurrentPriorityLevel(): PriorityLevel {
 }
 
 export function unstable_next<T>(callback: () => T): T {
-  let priorityLevel;
+  let priorityLevel: PriorityLevel;
   switch (currentPriorityLevel_DEPRECATED) {
     case ImmediatePriority:
     case UserBlockingPriority:

diff --git a/packages/shared/ReactPerformanceTrackProperties.js b/packages/shared/ReactPerformanceTrackProperties.js
@@ -19,7 +19,7 @@ const COMPLEX_ARRAY = 1;
 const PRIMITIVE_ARRAY = 2; // Primitive values only
 const ENTRIES_ARRAY = 3; // Tuple arrays of string and value (like Headers, Map, etc)
 function getArrayKind(array: Object): 0 | 1 | 2 | 3 {
-  let kind = EMPTY_ARRAY;
+  let kind: 0 | 1 | 2 | 3 = EMPTY_ARRAY;
   for (let i = 0; i < array.length; i++) {
     const value = array[i];
     if (typeof value === 'object' && value !== null) {

diff --git a/yarn.lock b/yarn.lock
@@ -9298,12 +9298,12 @@ flatted@^3.2.9:
   resolved "https://registry.yarnpkg.com/flatted/-/flatted-3.3.1.tgz#21db470729a6734d4997002f439cb308987f567a"
   integrity sha512-X8cqMLLie7KsNUDSdzeN8FYK9rEt4Dt67OsG/DNGnYTSDBG4uFAJFBnUeiV+zCVAvwFy56IjM9sH51jVaEhNxw==
 
-flow-bin@^0.266:
-  version "0.266.1"
-  resolved "https://registry.yarnpkg.com/flow-bin/-/flow-bin-0.266.1.tgz#8939be6fbd681c4ef8dc4873b22f4b79be76cb0a"
-  integrity sha512-c1lg1E8SDcuPSkrOeH0JTcNKMZOzXvqX2DuuXJ0amZec15uyuIi8QlGTO3OzYssMT/kwFdo5vviJqSUI/BNFbw==
+flow-bin@^0.267:
+  version "0.267.0"
+  resolved "https://registry.yarnpkg.com/flow-bin/-/flow-bin-0.267.0.tgz#a191375df35c768f1afaebfd0e25b06c8ab82a04"
+  integrity sha512-NsBcxdAqQauzgOaDf960M+eEnjcFS6FeMs93dEpkvQflwMlP4SRMdKQR8p5WzJJh07CXq9iQnxn+JjLN6kaLUw==
 
-flow-remove-types@^2.266:
+flow-remove-types@^2.267:
   version "2.279.0"
   resolved "https://registry.yarnpkg.com/flow-remove-types/-/flow-remove-types-2.279.0.tgz#3a3388d9158eba0f82c40d80d31d9640b883a3f5"
   integrity sha512-bPFloMR/A2b/r/sIsf7Ix0LaMicCJNjwhXc4xEEQVzJCIz5u7C7XDaEOXOiqveKlCYK7DcBNn6R01Cbbc9gsYA==