this commit makes the following changes to the way paths are handled:

- store paths on parents instead of containers
 - implement one central hub that all traversal paths and scopes get access to in order to abstract out access to common functions

src/babel/traversal/path/index.js

@@ -1,4 +1,5 @@
 import type File from "../../transformation/file";
+import type Hub from "../hub";
 import * as virtualTypes from "./lib/virtual-types";
 import traverse from "../index";
 import assign from "lodash/object/assign";
@@ -6,22 +7,21 @@ import Scope from "../scope";
 import * as t from "../../types";
 
 export default class NodePath {
-  constructor(parent, container, containerKey) {
-    this.containerKey = containerKey;
-    this.container    = container;
-    this.contexts     = [];
-    this.parent       = parent;
-    this.data         = {};
+  constructor(hub, parent) {
+    this.contexts = [];
+    this.parent   = parent;
+    this.data     = {};
+    this.hub      = hub;
   }
 
   /**
    * Description
    */
 
-  static get({ parentPath, parent, container, containerKey, key }) {
+  static get({ hub, parentPath, parent, container, containerKey, key }) {
     var targetNode = container[key];
-    var paths = container._paths = container._paths || [];
-    var path;
+    var paths = parent._paths = parent._paths || [];
+    var path
 
     for (var i = 0; i < paths.length; i++) {
       var pathCheck = paths[i];
@@ -32,11 +32,11 @@ export default class NodePath {
     }
 
     if (!path) {
-      path = new NodePath(parent, container, containerKey);
+      path = new NodePath(hub, parent);
       paths.push(path);
     }
 
-    path.setup(parentPath, key);
+    path.setup(parentPath, container, containerKey, key);
 
     return path;
   }
@@ -45,12 +45,12 @@ export default class NodePath {
    * Description
    */
 
-  static getScope(path: NodePath, scope: Scope, file?: File) {
+  static getScope(path: NodePath, scope: Scope, hub?: Hub) {
     var ourScope = scope;
 
     // we're entering a new scope so let's construct it!
     if (path.isScope()) {
-      ourScope = new Scope(path, scope, file);
+      ourScope = new Scope(path, scope, hub);
     }
 
     return ourScope;

src/babel/traversal/scope/index.js

@@ -1,7 +1,7 @@
 import includes from "lodash/collection/includes";
 import repeating from "repeating";
 import type NodePath from "../path";
-import type File from "../../transformation/file";
+import type Hub from "../hub";
 import traverse from "../index";
 import defaults from "lodash/object/defaults";
 import * as messages from "../../messages";
@@ -140,7 +140,7 @@ export default class Scope {
    * within.
    */
 
-  constructor(path: NodePath, parent?: Scope, file?: File) {
+  constructor(path: NodePath, parent?: Scope, hub?: Hub) {
     if (parent && parent.block === path.node) {
       return parent;
     }
@@ -153,7 +153,7 @@ export default class Scope {
     }
 
     this.parent = parent;
-    this.file   = parent ? parent.file : file;
+    this.hub    = parent ? parent.hub : hub;
 
     this.parentBlock = path.parent;
     this.block       = path.node;
@@ -177,17 +177,6 @@ export default class Scope {
     traverse(node, opts, this, state, this.path);
   }
 
-
-  /**
-   * Since `Scope` instances are unique to their traversal we need some other
-   * way to compare if scopes are the same. Here we just compare `this.bindings`
-   * as it will be the same across all instances.
-   */
-
-  is(scope) {
-    return this.bindings === scope.bindings;
-  }
-
   /**
    * Description
    */
@@ -344,7 +333,7 @@ export default class Scope {
     if (!duplicate) duplicate = local.kind === "param" && (kind === "let" || kind === "const");
 
     if (duplicate) {
-      throw this.file.errorWithNode(id, messages.get("scopeDuplicateDeclaration", name), TypeError);
+      throw this.hub.file.errorWithNode(id, messages.get("scopeDuplicateDeclaration", name), TypeError);
     }
   }
 
@@ -374,7 +363,7 @@ export default class Scope {
       state.binding.name = newName;
     }
 
-    var file = this.file;
+    var file = this.hub.file;
     if (file) {
       this._renameFromMap(file.moduleFormatter.localImports, oldName, newName, state.binding);
       //this._renameFromMap(file.moduleFormatter.localExports, oldName, newName);
@@ -414,7 +403,7 @@ export default class Scope {
    */
 
   toArray(node: Object, i?: number) {
-    var file = this.file;
+    var file = this.hub.file;
 
     if (t.isIdentifier(node)) {
       var binding = this.getBinding(node.name);
@@ -436,7 +425,7 @@ export default class Scope {
     } else if (i) {
       args.push(t.literal(i));
       helperName = "sliced-to-array";
-      if (this.file.isLoose("es6.forOf")) helperName += "-loose";
+      if (this.hub.file.isLoose("es6.forOf")) helperName += "-loose";
     }
     return t.callExpression(file.addHelper(helperName), args);
   }
@@ -716,7 +705,7 @@ export default class Scope {
       declar._generated = true;
       declar._blockHoist = 2;
 
-      this.file.attachAuxiliaryComment(declar);
+      this.hub.file.attachAuxiliaryComment(declar);
 
       var [declarPath] = path.unshiftContainer("body", [declar]);
       this.registerBinding(kind, declarPath);