Not all versions of fiber.dependencies have `contextDependency.memo…

…izedValue`

I considered polyfilling `memoizedValue` but it seems safer to call this out when we read the context value.
And also to avoid deopts due to using expando properties on the ContextDependency type in old versions.

packages/react-debug-tools/src/ReactDebugHooks.js

@@ -1109,6 +1109,29 @@ export function inspectHooksOfFiber(
   currentHook = (fiber.memoizedState: Hook);
   currentFiber = fiber;
 
+  if (hasOwnProperty.call(currentFiber, 'dependencies')) {
+    // $FlowFixMe[incompatible-use]: Flow thinks hasOwnProperty might have nulled `currentFiber`
+    const dependencies = currentFiber.dependencies;
+    currentContextDependency =
+      dependencies !== null ? dependencies.firstContext : null;
+  } else if (hasOwnProperty.call(currentFiber, 'dependencies_old')) {
+    const dependencies: Dependencies = (currentFiber: any).dependencies_old;
+    currentContextDependency =
+      dependencies !== null ? dependencies.firstContext : null;
+  } else if (hasOwnProperty.call(currentFiber, 'dependencies_new')) {
+    const dependencies: Dependencies = (currentFiber: any).dependencies_new;
+    currentContextDependency =
+      dependencies !== null ? dependencies.firstContext : null;
+  } else if (hasOwnProperty.call(currentFiber, 'contextDependencies')) {
+    const contextDependencies = (currentFiber: any).contextDependencies;
+    currentContextDependency =
+      contextDependencies !== null ? contextDependencies.first : null;
+  } else {
+    throw new Error(
+      'Unsupported React version. This is a bug in React Debug Tools.',
+    );
+  }
+
   const type = fiber.type;
   let props = fiber.memoizedProps;
   if (type !== fiber.elementType) {
@@ -1118,30 +1141,11 @@ export function inspectHooksOfFiber(
   // Only used for versions of React without memoized context value in context dependencies.
   const contextMap = new Map<ReactContext<any>, any>();
   try {
-    if (hasOwnProperty.call(currentFiber, 'dependencies')) {
-      // $FlowFixMe[incompatible-use]: Flow thinks hasOwnProperty might have nulled `currentFiber`
-      const dependencies = currentFiber.dependencies;
-      currentContextDependency =
-        dependencies !== null ? dependencies.firstContext : null;
-    } else if (hasOwnProperty.call(currentFiber, 'dependencies_old')) {
-      const dependencies: Dependencies = (currentFiber: any).dependencies_old;
-      currentContextDependency =
-        dependencies !== null ? dependencies.firstContext : null;
-      setupContexts(contextMap, fiber);
-    } else if (hasOwnProperty.call(currentFiber, 'dependencies_new')) {
-      const dependencies: Dependencies = (currentFiber: any).dependencies_new;
-      currentContextDependency =
-        dependencies !== null ? dependencies.firstContext : null;
-      setupContexts(contextMap, fiber);
-    } else if (hasOwnProperty.call(currentFiber, 'contextDependencies')) {
-      const contextDependencies = (currentFiber: any).contextDependencies;
-      currentContextDependency =
-        contextDependencies !== null ? contextDependencies.first : null;
+    if (
+      currentContextDependency !== null &&
+      !hasOwnProperty.call(currentContextDependency, 'memoizedValue')
+    ) {
       setupContexts(contextMap, fiber);
-    } else {
-      throw new Error(
-        'Unsupported React version. This is a bug in React Debug Tools.',
-      );
     }
 
     if (fiber.tag === ForwardRef) {