Re-land "Clean up host pointers in level 2 of clean-up flag (#21112)"

This re-lands commit 8ed0c85.

Author: acdlite

packages/react-reconciler/src/ReactFiberCommitWork.new.js

@@ -1382,6 +1382,18 @@ function detachFiberAfterEffects(fiber: Fiber) {
 fiber.deletions=null;
 fiber.sibling=null;
 
+// The `stateNode` is cyclical because on host nodes it points to the host
+// tree, which has its own pointers to children, parents, and siblings.
+// The other host nodes also point back to fibers, so we should detach that
+// one, too.
+if(fiber.tag===HostComponent){
+consthostInstance: Instance=fiber.stateNode;
+if(hostInstance!==null){
+detachDeletedInstance(hostInstance);
+}
+}
+fiber.stateNode=null;
+
 // I'm intentionally not clearing the `return` field in this level. We
 // already disconnect the `return` pointer at the root of the deleted
 // subtree (in `detachFiberMutation`). Besides, `return` by itself is not
@@ -1400,15 +1412,6 @@ function detachFiberAfterEffects(fiber: Fiber) {
 // The purpose of this branch is to be super aggressive so we can measure
 // if there's any difference in memory impact. If there is, that could
 // indicate a React leak we don't know about.
-
-// For host components, disconnect host instance -> fiber pointer.
-if(fiber.tag===HostComponent){
-consthostInstance: Instance=fiber.stateNode;
-if(hostInstance!==null){
-detachDeletedInstance(hostInstance);
-}
-}
-
 fiber.return=null;
 fiber.dependencies=null;
 fiber.memoizedProps=null;

packages/react-reconciler/src/ReactFiberCommitWork.old.js

@@ -1382,6 +1382,18 @@ function detachFiberAfterEffects(fiber: Fiber) {
 fiber.deletions=null;
 fiber.sibling=null;
 
+// The `stateNode` is cyclical because on host nodes it points to the host
+// tree, which has its own pointers to children, parents, and siblings.
+// The other host nodes also point back to fibers, so we should detach that
+// one, too.
+if(fiber.tag===HostComponent){
+consthostInstance: Instance=fiber.stateNode;
+if(hostInstance!==null){
+detachDeletedInstance(hostInstance);
+}
+}
+fiber.stateNode=null;
+
 // I'm intentionally not clearing the `return` field in this level. We
 // already disconnect the `return` pointer at the root of the deleted
 // subtree (in `detachFiberMutation`). Besides, `return` by itself is not
@@ -1400,15 +1412,6 @@ function detachFiberAfterEffects(fiber: Fiber) {
 // The purpose of this branch is to be super aggressive so we can measure
 // if there's any difference in memory impact. If there is, that could
 // indicate a React leak we don't know about.
-
-// For host components, disconnect host instance -> fiber pointer.
-if(fiber.tag===HostComponent){
-consthostInstance: Instance=fiber.stateNode;
-if(hostInstance!==null){
-detachDeletedInstance(hostInstance);
-}
-}
-
 fiber.return=null;
 fiber.dependencies=null;
 fiber.memoizedProps=null;