From 6c32fea3ae42b6ca57f79bdda70dba2c7f23c23f Mon Sep 17 00:00:00 2001
From: Dominic Gannaway <dg@domgan.com>
Date: Fri, 7 Apr 2017 22:42:05 +0100
Subject: [PATCH 01/15] made createFiber create a constructed FiberNode object

---
 src/renderers/shared/fiber/ReactFiber.js | 75 ++++++++++++------------
 1 file changed, 36 insertions(+), 39 deletions(-)

diff --git a/src/renderers/shared/fiber/ReactFiber.js b/src/renderers/shared/fiber/ReactFiber.js
index faf8f95d3704..638b7bfaceb2 100644
--- a/src/renderers/shared/fiber/ReactFiber.js
+++ b/src/renderers/shared/fiber/ReactFiber.js
@@ -163,6 +163,41 @@ if (__DEV__) {
   var debugCounter = 1;
 }
 
+function FiberNode(tag: TypeOfWork, key: null | string): Fiber {
+    // Instance
+    this.tag = tag;
+    this.key = key;
+    this.type = null;
+    this.stateNode = null;
+
+    // Fiber
+    this.return = null;
+    this.child = null;
+    this.sibling = null;
+    this.index = 0;
+
+    this.ref = null;
+
+    this.pendingProps = null;
+    this.memoizedProps = null;
+    this.updateQueue = null;
+    this.memoizedState = null;
+
+    // Effects
+    this.effectTag = NoEffect;
+    this.nextEffect = null;
+    this.firstEffect = null;
+    this.lastEffect = null;
+
+    this.pendingWorkPriority = NoWork;
+    this.progressedPriority = NoWork;
+    this.progressedChild = null;
+    this.progressedFirstDeletion = null;
+    this.progressedLastDeletion = null;
+
+    this.alternate = null;
+}
+
 // This is a constructor of a POJO instead of a constructor function for a few
 // reasons:
 // 1) Nobody should add any instance methods on this. Instance methods can be
@@ -177,45 +212,7 @@ if (__DEV__) {
 // 5) It should be easy to port this to a C struct and keep a C implementation
 //    compatible.
 var createFiber = function(tag: TypeOfWork, key: null | string): Fiber {
-  var fiber: Fiber = {
-    // Instance
-
-    tag: tag,
-
-    key: key,
-
-    type: null,
-
-    stateNode: null,
-
-    // Fiber
-
-    return: null,
-
-    child: null,
-    sibling: null,
-    index: 0,
-
-    ref: null,
-
-    pendingProps: null,
-    memoizedProps: null,
-    updateQueue: null,
-    memoizedState: null,
-
-    effectTag: NoEffect,
-    nextEffect: null,
-    firstEffect: null,
-    lastEffect: null,
-
-    pendingWorkPriority: NoWork,
-    progressedPriority: NoWork,
-    progressedChild: null,
-    progressedFirstDeletion: null,
-    progressedLastDeletion: null,
-
-    alternate: null,
-  };
+  var fiber: Fiber = new FiberNode(tag, key);
 
   if (__DEV__) {
     fiber._debugID = debugCounter++;

From 83830dab257c2a0fef9ae7682090770777b0f72b Mon Sep 17 00:00:00 2001
From: Dominic Gannaway <dg@domgan.com>
Date: Fri, 7 Apr 2017 22:46:19 +0100
Subject: [PATCH 02/15] updated comment

---
 src/renderers/shared/fiber/ReactFiber.js | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/src/renderers/shared/fiber/ReactFiber.js b/src/renderers/shared/fiber/ReactFiber.js
index 638b7bfaceb2..f2faf53c07d3 100644
--- a/src/renderers/shared/fiber/ReactFiber.js
+++ b/src/renderers/shared/fiber/ReactFiber.js
@@ -198,18 +198,16 @@ function FiberNode(tag: TypeOfWork, key: null | string): Fiber {
     this.alternate = null;
 }
 
-// This is a constructor of a POJO instead of a constructor function for a few
-// reasons:
+// This is now a constructor function again, rather than a POJO constructor, still
+// please ensure we do the following:
 // 1) Nobody should add any instance methods on this. Instance methods can be
 //    more difficult to predict when they get optimized and they are almost
 //    never inlined properly in static compilers.
 // 2) Nobody should rely on `instanceof Fiber` for type testing. We should
 //    always know when it is a fiber.
-// 3) We can easily go from a createFiber call to calling a constructor if that
-//    is faster. The opposite is not true.
-// 4) We might want to experiment with using numeric keys since they are easier
+// 3) We might want to experiment with using numeric keys since they are easier
 //    to optimize in a non-JIT environment.
-// 5) It should be easy to port this to a C struct and keep a C implementation
+// 4) It should be easy to port this to a C struct and keep a C implementation
 //    compatible.
 var createFiber = function(tag: TypeOfWork, key: null | string): Fiber {
   var fiber: Fiber = new FiberNode(tag, key);

From f6fedc36b3d432ba58c40adeb35a374e444d478e Mon Sep 17 00:00:00 2001
From: Dominic Gannaway <dg@domgan.com>
Date: Fri, 7 Apr 2017 23:18:19 +0100
Subject: [PATCH 03/15] satisfying flow and prettier

---
 src/renderers/shared/fiber/ReactFiber.js | 66 ++++++++++++------------
 1 file changed, 33 insertions(+), 33 deletions(-)

diff --git a/src/renderers/shared/fiber/ReactFiber.js b/src/renderers/shared/fiber/ReactFiber.js
index f2faf53c07d3..46c3ea9b37c9 100644
--- a/src/renderers/shared/fiber/ReactFiber.js
+++ b/src/renderers/shared/fiber/ReactFiber.js
@@ -163,39 +163,39 @@ if (__DEV__) {
   var debugCounter = 1;
 }
 
-function FiberNode(tag: TypeOfWork, key: null | string): Fiber {
-    // Instance
-    this.tag = tag;
-    this.key = key;
-    this.type = null;
-    this.stateNode = null;
-
-    // Fiber
-    this.return = null;
-    this.child = null;
-    this.sibling = null;
-    this.index = 0;
-
-    this.ref = null;
-
-    this.pendingProps = null;
-    this.memoizedProps = null;
-    this.updateQueue = null;
-    this.memoizedState = null;
-
-    // Effects
-    this.effectTag = NoEffect;
-    this.nextEffect = null;
-    this.firstEffect = null;
-    this.lastEffect = null;
-
-    this.pendingWorkPriority = NoWork;
-    this.progressedPriority = NoWork;
-    this.progressedChild = null;
-    this.progressedFirstDeletion = null;
-    this.progressedLastDeletion = null;
-
-    this.alternate = null;
+function FiberNode(tag: TypeOfWork, key: null | string) {
+  // Instance
+  this.tag = tag;
+  this.key = key;
+  this.type = null;
+  this.stateNode = null;
+
+  // Fiber
+  this.return = null;
+  this.child = null;
+  this.sibling = null;
+  this.index = 0;
+
+  this.ref = null;
+
+  this.pendingProps = null;
+  this.memoizedProps = null;
+  this.updateQueue = null;
+  this.memoizedState = null;
+
+  // Effects
+  this.effectTag = NoEffect;
+  this.nextEffect = null;
+  this.firstEffect = null;
+  this.lastEffect = null;
+
+  this.pendingWorkPriority = NoWork;
+  this.progressedPriority = NoWork;
+  this.progressedChild = null;
+  this.progressedFirstDeletion = null;
+  this.progressedLastDeletion = null;
+
+  this.alternate = null;
 }
 
 // This is now a constructor function again, rather than a POJO constructor, still

From 180bf7641c9f32dbeec63f9ce13d17f346952aa1 Mon Sep 17 00:00:00 2001
From: Dominic Gannaway <dg@domgan.com>
Date: Fri, 7 Apr 2017 23:26:50 +0100
Subject: [PATCH 04/15] better comments :)

---
 src/renderers/shared/fiber/ReactFiber.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/renderers/shared/fiber/ReactFiber.js b/src/renderers/shared/fiber/ReactFiber.js
index 46c3ea9b37c9..985ddb005c12 100644
--- a/src/renderers/shared/fiber/ReactFiber.js
+++ b/src/renderers/shared/fiber/ReactFiber.js
@@ -198,7 +198,7 @@ function FiberNode(tag: TypeOfWork, key: null | string) {
   this.alternate = null;
 }
 
-// This is now a constructor function again, rather than a POJO constructor, still
+// This is a constructor function, rather than a POJO constructor, still
 // please ensure we do the following:
 // 1) Nobody should add any instance methods on this. Instance methods can be
 //    more difficult to predict when they get optimized and they are almost

From 220735717b1643976f06c32869a8a63b4d5f1993 Mon Sep 17 00:00:00 2001
From: Dominic Gannaway <dg@domgan.com>
Date: Mon, 10 Apr 2017 12:40:26 +0100
Subject: [PATCH 05/15] fixes flow error

---
 src/renderers/shared/fiber/ReactFiber.js | 24 +++++++++++-------------
 1 file changed, 11 insertions(+), 13 deletions(-)

diff --git a/src/renderers/shared/fiber/ReactFiber.js b/src/renderers/shared/fiber/ReactFiber.js
index 985ddb005c12..1163f54e336c 100644
--- a/src/renderers/shared/fiber/ReactFiber.js
+++ b/src/renderers/shared/fiber/ReactFiber.js
@@ -196,6 +196,16 @@ function FiberNode(tag: TypeOfWork, key: null | string) {
   this.progressedLastDeletion = null;
 
   this.alternate = null;
+
+  if (__DEV__) {
+    this._debugID = debugCounter++;
+    this._debugSource = null;
+    this._debugOwner = null;
+    this._debugIsCurrentlyTiming = false;
+    if (typeof Object.preventExtensions === 'function') {
+      Object.preventExtensions(this);
+    }
+  }
 }
 
 // This is a constructor function, rather than a POJO constructor, still
@@ -210,19 +220,7 @@ function FiberNode(tag: TypeOfWork, key: null | string) {
 // 4) It should be easy to port this to a C struct and keep a C implementation
 //    compatible.
 var createFiber = function(tag: TypeOfWork, key: null | string): Fiber {
-  var fiber: Fiber = new FiberNode(tag, key);
-
-  if (__DEV__) {
-    fiber._debugID = debugCounter++;
-    fiber._debugSource = null;
-    fiber._debugOwner = null;
-    fiber._debugIsCurrentlyTiming = false;
-    if (typeof Object.preventExtensions === 'function') {
-      Object.preventExtensions(fiber);
-    }
-  }
-
-  return fiber;
+  return new FiberNode(tag, key);
 };
 
 function shouldConstruct(Component) {

From 61b3eb1004413a7cddd92bcf648ed74eb04a5f9b Mon Sep 17 00:00:00 2001
From: Dominic Gannaway <dg@domgan.com>
Date: Mon, 10 Apr 2017 12:41:42 +0100
Subject: [PATCH 06/15] updates comment

---
 src/renderers/shared/fiber/ReactFiber.js | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/renderers/shared/fiber/ReactFiber.js b/src/renderers/shared/fiber/ReactFiber.js
index 1163f54e336c..cae89bd68126 100644
--- a/src/renderers/shared/fiber/ReactFiber.js
+++ b/src/renderers/shared/fiber/ReactFiber.js
@@ -217,7 +217,9 @@ function FiberNode(tag: TypeOfWork, key: null | string) {
 //    always know when it is a fiber.
 // 3) We might want to experiment with using numeric keys since they are easier
 //    to optimize in a non-JIT environment.
-// 4) It should be easy to port this to a C struct and keep a C implementation
+// 4) We can easily go from a constructor to a createFiber object literal if that
+//    is faster.
+// 5) It should be easy to port this to a C struct and keep a C implementation
 //    compatible.
 var createFiber = function(tag: TypeOfWork, key: null | string): Fiber {
   return new FiberNode(tag, key);

From c020982c5fe62446667f6f933c834366c3f009b3 Mon Sep 17 00:00:00 2001
From: Dominic Gannaway <dg@domgan.com>
Date: Mon, 10 Apr 2017 13:04:39 +0100
Subject: [PATCH 07/15] converted function constructor to a ES2015 class

---
 src/renderers/shared/fiber/ReactFiber.js | 147 +++++++++++------------
 1 file changed, 73 insertions(+), 74 deletions(-)

diff --git a/src/renderers/shared/fiber/ReactFiber.js b/src/renderers/shared/fiber/ReactFiber.js
index cae89bd68126..dc77a7e91e91 100644
--- a/src/renderers/shared/fiber/ReactFiber.js
+++ b/src/renderers/shared/fiber/ReactFiber.js
@@ -55,12 +55,12 @@ if (__DEV__) {
 
 // A Fiber is work on a Component that needs to be done or was done. There can
 // be more than one per component.
-export type Fiber = {
+export class Fiber {
   // __DEV__ only
-  _debugID?: DebugID,
-  _debugSource?: Source | null,
-  _debugOwner?: Fiber | ReactInstance | null, // Stack compatible
-  _debugIsCurrentlyTiming?: boolean,
+  _debugID: DebugID;
+  _debugSource: Source | null;
+  _debugOwner: Fiber | ReactInstance | null; // Stack compatible
+  _debugIsCurrentlyTiming: boolean;
 
   // These first fields are conceptually members of an Instance. This used to
   // be split into a separate type and intersected with the other Fiber fields,
@@ -73,16 +73,16 @@ export type Fiber = {
   // minimize the number of objects created during the initial render.
 
   // Tag identifying the type of fiber.
-  tag: TypeOfWork,
+  tag: TypeOfWork;
 
   // Unique identifier of this child.
-  key: null | string,
+  key: null | string;
 
   // The function/class/module associated with this fiber.
-  type: any,
+  type: any;
 
   // The local state associated with this fiber.
-  stateNode: any,
+  stateNode: any;
 
   // Conceptual aliases
   // parent : Instance -> return The parent happens to be the same as the
@@ -94,120 +94,119 @@ export type Fiber = {
   // This is effectively the parent, but there can be multiple parents (two)
   // so this is only the parent of the thing we're currently processing.
   // It is conceptually the same as the return address of a stack frame.
-  return: Fiber | null,
+  return: Fiber | null;
 
   // Singly Linked List Tree Structure.
-  child: Fiber | null,
-  sibling: Fiber | null,
-  index: number,
+  child: Fiber | null;
+  sibling: Fiber | null;
+  index: number;
 
   // The ref last used to attach this node.
   // I'll avoid adding an owner field for prod and model that as functions.
-  ref: null | (((handle: mixed) => void) & {_stringRef: ?string}),
+  ref: null | (((handle: mixed) => void) & {_stringRef: ?string});
 
   // Input is the data coming into process this fiber. Arguments. Props.
-  pendingProps: any, // This type will be more specific once we overload the tag.
+  pendingProps: any; // This type will be more specific once we overload the tag.
   // TODO: I think that there is a way to merge pendingProps and memoizedProps.
-  memoizedProps: any, // The props used to create the output.
+  memoizedProps: any; // The props used to create the output.
 
   // A queue of state updates and callbacks.
-  updateQueue: UpdateQueue | null,
+  updateQueue: UpdateQueue | null;
 
   // The state used to create the output
-  memoizedState: any,
+  memoizedState: any;
 
   // Effect
-  effectTag: TypeOfSideEffect,
+  effectTag: TypeOfSideEffect;
 
   // Singly linked list fast path to the next fiber with side-effects.
-  nextEffect: Fiber | null,
+  nextEffect: Fiber | null;
 
   // The first and last fiber with side-effect within this subtree. This allows
   // us to reuse a slice of the linked list when we reuse the work done within
   // this fiber.
-  firstEffect: Fiber | null,
-  lastEffect: Fiber | null,
+  firstEffect: Fiber | null;
+  lastEffect: Fiber | null;
 
   // This will be used to quickly determine if a subtree has no pending changes.
-  pendingWorkPriority: PriorityLevel,
+  pendingWorkPriority: PriorityLevel;
 
   // This value represents the priority level that was last used to process this
   // component. This indicates whether it is better to continue from the
   // progressed work or if it is better to continue from the current state.
-  progressedPriority: PriorityLevel,
+  progressedPriority: PriorityLevel;
 
   // If work bails out on a Fiber that already had some work started at a lower
   // priority, then we need to store the progressed work somewhere. This holds
   // the started child set until we need to get back to working on it. It may
   // or may not be the same as the "current" child.
-  progressedChild: Fiber | null,
+  progressedChild: Fiber | null;
 
   // When we reconcile children onto progressedChild it is possible that we have
   // to delete some child fibers. We need to keep track of this side-effects so
   // that if we continue later on, we have to include those effects. Deletions
   // are added in the reverse order from sibling pointers.
-  progressedFirstDeletion: Fiber | null,
-  progressedLastDeletion: Fiber | null,
+  progressedFirstDeletion: Fiber | null;
+  progressedLastDeletion: Fiber | null;
 
   // This is a pooled version of a Fiber. Every fiber that gets updated will
   // eventually have a pair. There are cases when we can clean up pairs to save
   // memory if we need to.
-  alternate: Fiber | null,
+  alternate: Fiber | null;
 
   // Conceptual aliases
   // workInProgress : Fiber ->  alternate The alternate used for reuse happens
   // to be the same as work in progress.
+  constructor(tag: TypeOfWork, key: null | string) {
+    // Instance
+    this.tag = tag;
+    this.key = key;
+    this.type = null;
+    this.stateNode = null;
+
+    // Fiber
+    this.return = null;
+    this.child = null;
+    this.sibling = null;
+    this.index = 0;
+
+    this.ref = null;
+
+    this.pendingProps = null;
+    this.memoizedProps = null;
+    this.updateQueue = null;
+    this.memoizedState = null;
+
+    // Effects
+    this.effectTag = NoEffect;
+    this.nextEffect = null;
+    this.firstEffect = null;
+    this.lastEffect = null;
+
+    this.pendingWorkPriority = NoWork;
+    this.progressedPriority = NoWork;
+    this.progressedChild = null;
+    this.progressedFirstDeletion = null;
+    this.progressedLastDeletion = null;
+
+    this.alternate = null;
+
+    if (__DEV__) {
+      this._debugID = debugCounter++;
+      this._debugSource = null;
+      this._debugOwner = null;
+      this._debugIsCurrentlyTiming = false;
+      if (typeof Object.preventExtensions === 'function') {
+        Object.preventExtensions(this);
+      }
+    }
+  }
 };
 
 if (__DEV__) {
   var debugCounter = 1;
 }
 
-function FiberNode(tag: TypeOfWork, key: null | string) {
-  // Instance
-  this.tag = tag;
-  this.key = key;
-  this.type = null;
-  this.stateNode = null;
-
-  // Fiber
-  this.return = null;
-  this.child = null;
-  this.sibling = null;
-  this.index = 0;
-
-  this.ref = null;
-
-  this.pendingProps = null;
-  this.memoizedProps = null;
-  this.updateQueue = null;
-  this.memoizedState = null;
-
-  // Effects
-  this.effectTag = NoEffect;
-  this.nextEffect = null;
-  this.firstEffect = null;
-  this.lastEffect = null;
-
-  this.pendingWorkPriority = NoWork;
-  this.progressedPriority = NoWork;
-  this.progressedChild = null;
-  this.progressedFirstDeletion = null;
-  this.progressedLastDeletion = null;
-
-  this.alternate = null;
-
-  if (__DEV__) {
-    this._debugID = debugCounter++;
-    this._debugSource = null;
-    this._debugOwner = null;
-    this._debugIsCurrentlyTiming = false;
-    if (typeof Object.preventExtensions === 'function') {
-      Object.preventExtensions(this);
-    }
-  }
-}
-
 // This is a constructor function, rather than a POJO constructor, still
 // please ensure we do the following:
 // 1) Nobody should add any instance methods on this. Instance methods can be
@@ -222,7 +221,7 @@ function FiberNode(tag: TypeOfWork, key: null | string) {
 // 5) It should be easy to port this to a C struct and keep a C implementation
 //    compatible.
 var createFiber = function(tag: TypeOfWork, key: null | string): Fiber {
-  return new FiberNode(tag, key);
+  return new Fiber(tag, key);
 };
 
 function shouldConstruct(Component) {

From 395d750f47528ea2f430db9e4a70a81efc55a294 Mon Sep 17 00:00:00 2001
From: Dominic Gannaway <dg@domgan.com>
Date: Mon, 10 Apr 2017 13:36:58 +0100
Subject: [PATCH 08/15] Revert "converted function constructor to a ES2015
 class"

This reverts commit c020982c5fe62446667f6f933c834366c3f009b3.
---
 src/renderers/shared/fiber/ReactFiber.js | 147 ++++++++++++-----------
 1 file changed, 74 insertions(+), 73 deletions(-)

diff --git a/src/renderers/shared/fiber/ReactFiber.js b/src/renderers/shared/fiber/ReactFiber.js
index dc77a7e91e91..cae89bd68126 100644
--- a/src/renderers/shared/fiber/ReactFiber.js
+++ b/src/renderers/shared/fiber/ReactFiber.js
@@ -55,12 +55,12 @@ if (__DEV__) {
 
 // A Fiber is work on a Component that needs to be done or was done. There can
 // be more than one per component.
-export class Fiber {
+export type Fiber = {
   // __DEV__ only
-  _debugID: DebugID;
-  _debugSource: Source | null;
-  _debugOwner: Fiber | ReactInstance | null; // Stack compatible
-  _debugIsCurrentlyTiming: boolean;
+  _debugID?: DebugID,
+  _debugSource?: Source | null,
+  _debugOwner?: Fiber | ReactInstance | null, // Stack compatible
+  _debugIsCurrentlyTiming?: boolean,
 
   // These first fields are conceptually members of an Instance. This used to
   // be split into a separate type and intersected with the other Fiber fields,
@@ -73,16 +73,16 @@ export class Fiber {
   // minimize the number of objects created during the initial render.
 
   // Tag identifying the type of fiber.
-  tag: TypeOfWork;
+  tag: TypeOfWork,
 
   // Unique identifier of this child.
-  key: null | string;
+  key: null | string,
 
   // The function/class/module associated with this fiber.
-  type: any;
+  type: any,
 
   // The local state associated with this fiber.
-  stateNode: any;
+  stateNode: any,
 
   // Conceptual aliases
   // parent : Instance -> return The parent happens to be the same as the
@@ -94,119 +94,120 @@ export class Fiber {
   // This is effectively the parent, but there can be multiple parents (two)
   // so this is only the parent of the thing we're currently processing.
   // It is conceptually the same as the return address of a stack frame.
-  return: Fiber | null;
+  return: Fiber | null,
 
   // Singly Linked List Tree Structure.
-  child: Fiber | null;
-  sibling: Fiber | null;
-  index: number;
+  child: Fiber | null,
+  sibling: Fiber | null,
+  index: number,
 
   // The ref last used to attach this node.
   // I'll avoid adding an owner field for prod and model that as functions.
-  ref: null | (((handle: mixed) => void) & {_stringRef: ?string});
+  ref: null | (((handle: mixed) => void) & {_stringRef: ?string}),
 
   // Input is the data coming into process this fiber. Arguments. Props.
-  pendingProps: any; // This type will be more specific once we overload the tag.
+  pendingProps: any, // This type will be more specific once we overload the tag.
   // TODO: I think that there is a way to merge pendingProps and memoizedProps.
-  memoizedProps: any; // The props used to create the output.
+  memoizedProps: any, // The props used to create the output.
 
   // A queue of state updates and callbacks.
-  updateQueue: UpdateQueue | null;
+  updateQueue: UpdateQueue | null,
 
   // The state used to create the output
-  memoizedState: any;
+  memoizedState: any,
 
   // Effect
-  effectTag: TypeOfSideEffect;
+  effectTag: TypeOfSideEffect,
 
   // Singly linked list fast path to the next fiber with side-effects.
-  nextEffect: Fiber | null;
+  nextEffect: Fiber | null,
 
   // The first and last fiber with side-effect within this subtree. This allows
   // us to reuse a slice of the linked list when we reuse the work done within
   // this fiber.
-  firstEffect: Fiber | null;
-  lastEffect: Fiber | null;
+  firstEffect: Fiber | null,
+  lastEffect: Fiber | null,
 
   // This will be used to quickly determine if a subtree has no pending changes.
-  pendingWorkPriority: PriorityLevel;
+  pendingWorkPriority: PriorityLevel,
 
   // This value represents the priority level that was last used to process this
   // component. This indicates whether it is better to continue from the
   // progressed work or if it is better to continue from the current state.
-  progressedPriority: PriorityLevel;
+  progressedPriority: PriorityLevel,
 
   // If work bails out on a Fiber that already had some work started at a lower
   // priority, then we need to store the progressed work somewhere. This holds
   // the started child set until we need to get back to working on it. It may
   // or may not be the same as the "current" child.
-  progressedChild: Fiber | null;
+  progressedChild: Fiber | null,
 
   // When we reconcile children onto progressedChild it is possible that we have
   // to delete some child fibers. We need to keep track of this side-effects so
   // that if we continue later on, we have to include those effects. Deletions
   // are added in the reverse order from sibling pointers.
-  progressedFirstDeletion: Fiber | null;
-  progressedLastDeletion: Fiber | null;
+  progressedFirstDeletion: Fiber | null,
+  progressedLastDeletion: Fiber | null,
 
   // This is a pooled version of a Fiber. Every fiber that gets updated will
   // eventually have a pair. There are cases when we can clean up pairs to save
   // memory if we need to.
-  alternate: Fiber | null;
+  alternate: Fiber | null,
 
   // Conceptual aliases
   // workInProgress : Fiber ->  alternate The alternate used for reuse happens
   // to be the same as work in progress.
-  constructor(tag: TypeOfWork, key: null | string) {
-    // Instance
-    this.tag = tag;
-    this.key = key;
-    this.type = null;
-    this.stateNode = null;
-
-    // Fiber
-    this.return = null;
-    this.child = null;
-    this.sibling = null;
-    this.index = 0;
-
-    this.ref = null;
-
-    this.pendingProps = null;
-    this.memoizedProps = null;
-    this.updateQueue = null;
-    this.memoizedState = null;
-
-    // Effects
-    this.effectTag = NoEffect;
-    this.nextEffect = null;
-    this.firstEffect = null;
-    this.lastEffect = null;
-
-    this.pendingWorkPriority = NoWork;
-    this.progressedPriority = NoWork;
-    this.progressedChild = null;
-    this.progressedFirstDeletion = null;
-    this.progressedLastDeletion = null;
-
-    this.alternate = null;
-
-    if (__DEV__) {
-      this._debugID = debugCounter++;
-      this._debugSource = null;
-      this._debugOwner = null;
-      this._debugIsCurrentlyTiming = false;
-      if (typeof Object.preventExtensions === 'function') {
-        Object.preventExtensions(this);
-      }
-    }
-  }
 };
 
 if (__DEV__) {
   var debugCounter = 1;
 }
 
+function FiberNode(tag: TypeOfWork, key: null | string) {
+  // Instance
+  this.tag = tag;
+  this.key = key;
+  this.type = null;
+  this.stateNode = null;
+
+  // Fiber
+  this.return = null;
+  this.child = null;
+  this.sibling = null;
+  this.index = 0;
+
+  this.ref = null;
+
+  this.pendingProps = null;
+  this.memoizedProps = null;
+  this.updateQueue = null;
+  this.memoizedState = null;
+
+  // Effects
+  this.effectTag = NoEffect;
+  this.nextEffect = null;
+  this.firstEffect = null;
+  this.lastEffect = null;
+
+  this.pendingWorkPriority = NoWork;
+  this.progressedPriority = NoWork;
+  this.progressedChild = null;
+  this.progressedFirstDeletion = null;
+  this.progressedLastDeletion = null;
+
+  this.alternate = null;
+
+  if (__DEV__) {
+    this._debugID = debugCounter++;
+    this._debugSource = null;
+    this._debugOwner = null;
+    this._debugIsCurrentlyTiming = false;
+    if (typeof Object.preventExtensions === 'function') {
+      Object.preventExtensions(this);
+    }
+  }
+}
+
 // This is a constructor function, rather than a POJO constructor, still
 // please ensure we do the following:
 // 1) Nobody should add any instance methods on this. Instance methods can be
@@ -221,7 +222,7 @@ if (__DEV__) {
 // 5) It should be easy to port this to a C struct and keep a C implementation
 //    compatible.
 var createFiber = function(tag: TypeOfWork, key: null | string): Fiber {
-  return new Fiber(tag, key);
+  return new FiberNode(tag, key);
 };
 
 function shouldConstruct(Component) {

From d742a253cd928abd5d1706d4e6b702c373b7bdeb Mon Sep 17 00:00:00 2001
From: Dominic Gannaway <dg@domgan.com>
Date: Fri, 26 May 2017 22:31:22 +0100
Subject: [PATCH 09/15] fixed some merge conflict issues

---
 src/renderers/shared/fiber/ReactFiber.js | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/src/renderers/shared/fiber/ReactFiber.js b/src/renderers/shared/fiber/ReactFiber.js
index b511b5ff4936..ce163f3eea3c 100644
--- a/src/renderers/shared/fiber/ReactFiber.js
+++ b/src/renderers/shared/fiber/ReactFiber.js
@@ -50,7 +50,6 @@ var invariant = require('fbjs/lib/invariant');
 
 if (__DEV__) {
   var getComponentName = require('getComponentName');
-
   var hasBadMapPolyfill = false;
   try {
     const nonExtensibleObject = Object.preventExtensions({});
@@ -205,7 +204,7 @@ function FiberNode(
   this.memoizedProps = null;
   this.updateQueue = null;
   this.memoizedState = null;
-    
+
   this.internalContextTag = internalContextTag;
 
   // Effects
@@ -227,7 +226,7 @@ function FiberNode(
     this._debugSource = null;
     this._debugOwner = null;
     this._debugIsCurrentlyTiming = false;
-    if (typeof Object.preventExtensions === 'function') {
+    if (!hasBadMapPolyfill && typeof Object.preventExtensions === 'function') {
       Object.preventExtensions(this);
     }
   }
@@ -246,8 +245,12 @@ function FiberNode(
 //    is faster.
 // 5) It should be easy to port this to a C struct and keep a C implementation
 //    compatible.
-var createFiber = function(tag: TypeOfWork, key: null | string): Fiber {
-  return new FiberNode(tag, key);
+var createFiber = function(
+  tag: TypeOfWork,
+  key: null | string,
+  internalContextTag: TypeOfInternalContext,
+): Fiber {
+  return new FiberNode(tag, key, internalContextTag);
 };
 
 function shouldConstruct(Component) {

From 45e6375e9b0838566c891c017163b29e4f449fe9 Mon Sep 17 00:00:00 2001
From: Dominic Gannaway <dg@domgan.com>
Date: Fri, 26 May 2017 22:50:58 +0100
Subject: [PATCH 10/15] Flow....

---
 src/renderers/shared/fiber/ReactFiber.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/renderers/shared/fiber/ReactFiber.js b/src/renderers/shared/fiber/ReactFiber.js
index ce163f3eea3c..2331ecae9cf9 100644
--- a/src/renderers/shared/fiber/ReactFiber.js
+++ b/src/renderers/shared/fiber/ReactFiber.js
@@ -185,7 +185,7 @@ function FiberNode(
   tag: TypeOfWork,
   key: null | string,
   internalContextTag: TypeOfInternalContext,
-): Fiber {
+) {
   // Instance
   this.tag = tag;
   this.key = key;

From 332139ec377746a25533119722c4bcbdb8544f98 Mon Sep 17 00:00:00 2001
From: Dominic Gannaway <ADM@Dominics-MacBook-Pro.local>
Date: Wed, 9 Aug 2017 22:57:56 +0100
Subject: [PATCH 11/15] removed exact types to make flow pass

---
 src/renderers/shared/fiber/ReactFiber.js | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/src/renderers/shared/fiber/ReactFiber.js b/src/renderers/shared/fiber/ReactFiber.js
index 5d226c10e539..5f5beaf04baa 100644
--- a/src/renderers/shared/fiber/ReactFiber.js
+++ b/src/renderers/shared/fiber/ReactFiber.js
@@ -63,13 +63,7 @@ if (__DEV__) {
 
 // A Fiber is work on a Component that needs to be done or was done. There can
 // be more than one per component.
-export type Fiber = {|
-  // __DEV__ only
-  _debugID?: DebugID,
-  _debugSource?: Source | null,
-  _debugOwner?: Fiber | ReactInstance | null, // Stack compatible
-  _debugIsCurrentlyTiming?: boolean,
-
+export type Fiber = {
   // These first fields are conceptually members of an Instance. This used to
   // be split into a separate type and intersected with the other Fiber fields,
   // but until Flow fixes its intersection bugs, we've merged them into a
@@ -154,7 +148,12 @@ export type Fiber = {|
   // Conceptual aliases
   // workInProgress : Fiber ->  alternate The alternate used for reuse happens
   // to be the same as work in progress.
-|};
+  // __DEV__ only
+  _debugID?: DebugID,
+  _debugSource?: Source | null,
+  _debugOwner?: Fiber | ReactInstance | null, // Stack compatible
+  _debugIsCurrentlyTiming?: boolean,  
+};
 
 if (__DEV__) {
   var debugCounter = 1;
@@ -189,6 +188,7 @@ function FiberNode(
   // Effects
   this.effectTag = NoEffect;
   this.nextEffect = null;
+
   this.firstEffect = null;
   this.lastEffect = null;
 

From e6c208b82e57add1587cdc5de99a78df37c9a85c Mon Sep 17 00:00:00 2001
From: Dominic Gannaway <ADM@Dominics-MacBook-Pro.local>
Date: Wed, 9 Aug 2017 23:01:53 +0100
Subject: [PATCH 12/15] opted for $FlowFixMe instead

---
 src/renderers/shared/fiber/ReactFiber.js | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/renderers/shared/fiber/ReactFiber.js b/src/renderers/shared/fiber/ReactFiber.js
index 5f5beaf04baa..930daa862fb2 100644
--- a/src/renderers/shared/fiber/ReactFiber.js
+++ b/src/renderers/shared/fiber/ReactFiber.js
@@ -63,7 +63,7 @@ if (__DEV__) {
 
 // A Fiber is work on a Component that needs to be done or was done. There can
 // be more than one per component.
-export type Fiber = {
+export type Fiber = {|
   // These first fields are conceptually members of an Instance. This used to
   // be split into a separate type and intersected with the other Fiber fields,
   // but until Flow fixes its intersection bugs, we've merged them into a
@@ -153,7 +153,7 @@ export type Fiber = {
   _debugSource?: Source | null,
   _debugOwner?: Fiber | ReactInstance | null, // Stack compatible
   _debugIsCurrentlyTiming?: boolean,  
-};
+|};
 
 if (__DEV__) {
   var debugCounter = 1;
@@ -225,6 +225,7 @@ var createFiber = function(
   key: null | string,
   internalContextTag: TypeOfInternalContext,
 ): Fiber {
+  // $FlowFixMe: the shapes are exact here but Flow doesn't like constructors
   return new FiberNode(tag, key, internalContextTag);
 };
 

From 1ca665bf8c9f5a0569733d62a843bcfcda0e4d2e Mon Sep 17 00:00:00 2001
From: Dominic Gannaway <dg@domgan.com>
Date: Wed, 9 Aug 2017 22:57:56 +0100
Subject: [PATCH 13/15] removed exact types to make flow pass

---
 src/renderers/shared/fiber/ReactFiber.js | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/src/renderers/shared/fiber/ReactFiber.js b/src/renderers/shared/fiber/ReactFiber.js
index 5d226c10e539..5f5beaf04baa 100644
--- a/src/renderers/shared/fiber/ReactFiber.js
+++ b/src/renderers/shared/fiber/ReactFiber.js
@@ -63,13 +63,7 @@ if (__DEV__) {
 
 // A Fiber is work on a Component that needs to be done or was done. There can
 // be more than one per component.
-export type Fiber = {|
-  // __DEV__ only
-  _debugID?: DebugID,
-  _debugSource?: Source | null,
-  _debugOwner?: Fiber | ReactInstance | null, // Stack compatible
-  _debugIsCurrentlyTiming?: boolean,
-
+export type Fiber = {
   // These first fields are conceptually members of an Instance. This used to
   // be split into a separate type and intersected with the other Fiber fields,
   // but until Flow fixes its intersection bugs, we've merged them into a
@@ -154,7 +148,12 @@ export type Fiber = {|
   // Conceptual aliases
   // workInProgress : Fiber ->  alternate The alternate used for reuse happens
   // to be the same as work in progress.
-|};
+  // __DEV__ only
+  _debugID?: DebugID,
+  _debugSource?: Source | null,
+  _debugOwner?: Fiber | ReactInstance | null, // Stack compatible
+  _debugIsCurrentlyTiming?: boolean,  
+};
 
 if (__DEV__) {
   var debugCounter = 1;
@@ -189,6 +188,7 @@ function FiberNode(
   // Effects
   this.effectTag = NoEffect;
   this.nextEffect = null;
+
   this.firstEffect = null;
   this.lastEffect = null;
 

From 4d9b22d00d3f7d768fc5dce1d021a804fb02e44e Mon Sep 17 00:00:00 2001
From: Dominic Gannaway <dg@domgan.com>
Date: Wed, 9 Aug 2017 23:01:53 +0100
Subject: [PATCH 14/15] opted for $FlowFixMe instead

---
 src/renderers/shared/fiber/ReactFiber.js | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/renderers/shared/fiber/ReactFiber.js b/src/renderers/shared/fiber/ReactFiber.js
index 5f5beaf04baa..930daa862fb2 100644
--- a/src/renderers/shared/fiber/ReactFiber.js
+++ b/src/renderers/shared/fiber/ReactFiber.js
@@ -63,7 +63,7 @@ if (__DEV__) {
 
 // A Fiber is work on a Component that needs to be done or was done. There can
 // be more than one per component.
-export type Fiber = {
+export type Fiber = {|
   // These first fields are conceptually members of an Instance. This used to
   // be split into a separate type and intersected with the other Fiber fields,
   // but until Flow fixes its intersection bugs, we've merged them into a
@@ -153,7 +153,7 @@ export type Fiber = {
   _debugSource?: Source | null,
   _debugOwner?: Fiber | ReactInstance | null, // Stack compatible
   _debugIsCurrentlyTiming?: boolean,  
-};
+|};
 
 if (__DEV__) {
   var debugCounter = 1;
@@ -225,6 +225,7 @@ var createFiber = function(
   key: null | string,
   internalContextTag: TypeOfInternalContext,
 ): Fiber {
+  // $FlowFixMe: the shapes are exact here but Flow doesn't like constructors
   return new FiberNode(tag, key, internalContextTag);
 };
 

From 1a35a20c1c11f0bd657cd83f9b219984391f05e8 Mon Sep 17 00:00:00 2001
From: Dominic Gannaway <dg@domgan.com>
Date: Wed, 9 Aug 2017 23:14:44 +0100
Subject: [PATCH 15/15] run prettier

---
 src/renderers/shared/fiber/ReactFiber.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/renderers/shared/fiber/ReactFiber.js b/src/renderers/shared/fiber/ReactFiber.js
index 930daa862fb2..2a07cf2dc636 100644
--- a/src/renderers/shared/fiber/ReactFiber.js
+++ b/src/renderers/shared/fiber/ReactFiber.js
@@ -152,7 +152,7 @@ export type Fiber = {|
   _debugID?: DebugID,
   _debugSource?: Source | null,
   _debugOwner?: Fiber | ReactInstance | null, // Stack compatible
-  _debugIsCurrentlyTiming?: boolean,  
+  _debugIsCurrentlyTiming?: boolean,
 |};
 
 if (__DEV__) {