From 80a3e664e66c6bb11f93ea90b9c48b1429d76444 Mon Sep 17 00:00:00 2001
From: Lee Byron <lee.byron@robinhood.com>
Date: Tue, 18 Sep 2018 20:36:18 -0700
Subject: [PATCH] WIP empty unwrapping

---
 src/List.js       |  2 ++
 src/Map.js        |  2 ++
 src/OrderedMap.js |  7 +++++--
 src/Stack.js      | 30 ++++++++++++++++--------------
 4 files changed, 25 insertions(+), 16 deletions(-)

diff --git a/src/List.js b/src/List.js
index 5f37846732..61507b5337 100644
--- a/src/List.js
+++ b/src/List.js
@@ -257,6 +257,8 @@ ListPrototype['@@transducer/result'] = function (obj) {
   return obj.asImmutable();
 };
 
+ListPrototype.__empty = emptyList;
+
 class VNode {
   constructor(array, ownerID) {
     this.array = array;
diff --git a/src/Map.js b/src/Map.js
index 9a3628c691..cbe7ed705e 100644
--- a/src/Map.js
+++ b/src/Map.js
@@ -185,6 +185,8 @@ MapPrototype['@@transducer/result'] = function (obj) {
   return obj.asImmutable();
 };
 
+MapPrototype.__empty = emptyMap;
+
 // #pragma Trie Nodes
 
 class ArrayMapNode {
diff --git a/src/OrderedMap.js b/src/OrderedMap.js
index 6da2d762b6..2ff216770a 100644
--- a/src/OrderedMap.js
+++ b/src/OrderedMap.js
@@ -93,8 +93,11 @@ export class OrderedMap extends Map {
 
 OrderedMap.isOrderedMap = isOrderedMap;
 
-OrderedMap.prototype[IS_ORDERED_SYMBOL] = true;
-OrderedMap.prototype[DELETE] = OrderedMap.prototype.remove;
+const OrderedMapPrototype = OrderedMap.prototype;
+OrderedMapPrototype[IS_ORDERED_SYMBOL] = true;
+OrderedMapPrototype[DELETE] = OrderedMapPrototype.remove;
+
+OrderedMapPrototype.__empty = emptyOrderedMap;
 
 function makeOrderedMap(map, list, ownerID, hash) {
   const omap = Object.create(OrderedMap.prototype);
diff --git a/src/Stack.js b/src/Stack.js
index 6a7a6f219f..05241a6191 100644
--- a/src/Stack.js
+++ b/src/Stack.js
@@ -192,6 +192,21 @@ export class Stack extends IndexedCollection {
   }
 }
 
+function makeStack(size, head, ownerID, hash) {
+  const map = Object.create(StackPrototype);
+  map.size = size;
+  map._head = head;
+  map.__ownerID = ownerID;
+  map.__hash = hash;
+  map.__altered = false;
+  return map;
+}
+
+let EMPTY_STACK;
+function emptyStack() {
+  return EMPTY_STACK || (EMPTY_STACK = makeStack(0));
+}
+
 Stack.isStack = isStack;
 
 const StackPrototype = Stack.prototype;
@@ -210,17 +225,4 @@ StackPrototype['@@transducer/result'] = function (obj) {
   return obj.asImmutable();
 };
 
-function makeStack(size, head, ownerID, hash) {
-  const map = Object.create(StackPrototype);
-  map.size = size;
-  map._head = head;
-  map.__ownerID = ownerID;
-  map.__hash = hash;
-  map.__altered = false;
-  return map;
-}
-
-let EMPTY_STACK;
-function emptyStack() {
-  return EMPTY_STACK || (EMPTY_STACK = makeStack(0));
-}
+StackPrototype.__empty = emptyStack;