adds an explicit IdentityMap construct

addon/-private/system/identity-map.js

@@ -0,0 +1,28 @@
+import RecordMap from './record-map';
+import EmptyObject from './empty-object';
+
+export default class IdentityMap {
+  constructor() {
+    this._map = new EmptyObject();
+  }
+
+  retrieve(modelName) {
+    let recordMap = this._map[modelName];
+
+    if (!recordMap) {
+      recordMap = this._map[modelName] = new RecordMap(modelName);
+    }
+
+    return recordMap;
+  }
+
+  clear() {
+    let recordMaps = this._map;
+    let keys = Object.keys(recordMaps);
+
+    for (let i = 0; i < keys.length; i++) {
+      let key = keys[i];
+      recordMaps[key].clear();
+    }
+  }
+}

addon/-private/system/class-meta.js → addon/-private/system/record-map.js

@@ -1,12 +1,8 @@
 import EmptyObject from 'ember-data/-private/system/empty-object';
 
-const NULL_RESOLUTION = new EmptyObject();
-
 export default class ClassMeta {
-  constructor(store, modelName) {
+  constructor(modelName) {
     this.modelName = modelName;
-    this._store = store;
-    this._modelClass = null;
     this._idToRecord = null;
     this._records = null;
     this._metadata = null;
@@ -24,17 +20,9 @@ export default class ClassMeta {
     return this._metadata || (this._metadata = new EmptyObject());
   }
 
-  get modelClass() {
-    if (!this._modelClass) {
-      this._modelClass = this._store.modelFor(this.modelName) || NULL_RESOLUTION;
-    }
-
-    return this._modelClass === NULL_RESOLUTION ? null : this._modelClass;
-  }
-
   /* deprecated way of accessing modelClass */
   get type() {
-    return this.modelClass;
+    throw new Error('RecordMap.type is no longer available');
   }
 
   clear() {

addon/-private/system/store.js

@@ -7,7 +7,7 @@ import Model from 'ember-data/model';
 import { instrument, assert, deprecate, warn, runInDebug } from "ember-data/-private/debug";
 import normalizeModelName from "ember-data/-private/system/normalize-model-name";
 import { InvalidError } from 'ember-data/adapters/errors';
-import ClassMeta from 'ember-data/-private/system/class-meta';
+import IdentityMap from 'ember-data/-private/system/identity-map';
 import {
   promiseArray,
   promiseObject
@@ -213,7 +213,7 @@ Store = Service.extend({
       store: this
     });
 
-    this._recordMaps = new EmptyObject();
+    this._identityMap = new IdentityMap();
     this._pendingSave = [];
     this._instanceCache = new ContainerInstanceCache(getOwner(this), this);
 
@@ -1665,13 +1665,7 @@ Store = Service.extend({
     assert('Passing classes to store methods has been removed. Please pass a dasherized string instead of '+ inspect(modelName), !modelName || typeof modelName === 'string');
 
     if (arguments.length === 0) {
-      let recordMaps = this._recordMaps;
-      let keys = Object.keys(recordMaps);
-
-      for (let i = 0; i < keys.length; i++) {
-        let key = keys[i];
-        recordMaps[key].clear();
-      }
+      this._identityMap.clear();
     } else {
       let trueModelName = this._classKeyFor(modelName);
       this._recordMapFor(trueModelName).clear();
@@ -1975,15 +1969,7 @@ Store = Service.extend({
   */
   _recordMapFor(modelName) {
     heimdall.increment(_recordMapFor);
-    let recordMaps = this._recordMaps;
-    let recordMap = recordMaps[modelName];
-
-    if (recordMap) { return recordMap; }
-
-    recordMap = new ClassMeta(this, modelName);
-    recordMaps[modelName] = recordMap;
-
-    return recordMap;
+    return this._identityMap.retrieve(modelName);
   },
 
   // ................