rewrite constants transformer

lib/6to5/transformation/transformers/es6/constants.js

@@ -5,83 +5,38 @@ var t        = require("../../../types");
 var _        = require("lodash");
 
 var visitor = {
-  enter: function (child, parent, scope, context, state) {
-    if (child._ignoreConstant) return;
-    if (t.isVariableDeclaration(child)) return;
+  enter: function (node, parent, scope, context, state) {
+    if (t.isDeclaration(node) || t.isAssignmentExpression(node)) {
+      var ids = t.getIds(node, true);
 
-    if (t.isVariableDeclarator(child) || t.isDeclaration(child) || t.isAssignmentExpression(child)) {
-      state.check(parent, state.getIds(child), scope);
+      for (var key in ids) {
+        var id = ids[key];
+
+        var constant = state.constants[key];
+
+        // no constant exists
+        if (!constant) continue;
+
+        // check if the assignment id matches the constant declaration id
+        // if it does then it was the id used to initially declare the
+        // constant so we can just ignore it
+        if (id === constant) continue;
+
+        throw state.file.errorWithNode(id, key + " is read-only");
+      }
+    } else if (t.isScope(node)) {
+      context.skip();
     }
   }
 };
 
-exports.Program =
-exports.BlockStatement =
-exports.ForInStatement =
-exports.ForOfStatement =
-exports.ForStatement = function (node, parent, scope, context, file) {
-  var hasConstants = false;
-  var constants = {};
-
-  /**
-   * Check the results of `util.getIds` as `names` generated from a
-   * node against it's parent.
-   */
-
-  var check = function (parent, names, scope) {
-    for (var name in names) {
-      var nameNode = names[name];
-      if (!_.has(constants, name)) continue;
-      if (parent && t.isBlockStatement(parent) && parent !== constants[name]) continue;
-
-      if (scope) {
-        var defined = scope.get(name);
-        if (defined && defined === nameNode) continue;
-      }
-
-      throw file.errorWithNode(nameNode, name + " is read-only");
-    }
-  };
-
-  var getIds = function (node) {
-    return t.getIds(node, true, ["MemberExpression"]);
-  };
-
-  /**
-   * Collect all constants in this scope.
-   */
-
-  _.each(node.body, function (child, parent) {
-    if (t.isExportDeclaration(child)) {
-      child = child.declaration;
-    }
-
-    if (t.isVariableDeclaration(child, { kind: "const" })) {
-      for (var i = 0; i < child.declarations.length; i++) {
-        var declar = child.declarations[i];
-
-        var ids = getIds(declar);
-        for (var name in ids) {
-          var nameNode = ids[name];
-
-          var names = {};
-          names[name] = nameNode;
-          check(parent, names);
-
-          constants[name] = parent;
-          hasConstants = true;
-        }
-
-        declar._ignoreConstant = true;
-      }
-
-      child._ignoreConstant = true;
-      child.kind = "let";
-    }
+exports.Scope = function (node, parent, scope, context, file) {
+  traverse(node, visitor, scope, {
+    constants: scope.getAllOfKind("const"),
+    file:      file
   });
-
-  if (!hasConstants) return;
-
-  var state = { check: check, getIds: getIds };
-  traverse(node, visitor, scope, state);
+};
+
+exports.VariableDeclaration = function (node) {
+  if (node.kind === "const") node.kind = "let";
 };

lib/6to5/traverse/scope.js

@@ -25,6 +25,7 @@ function Scope(block, parent, file) {
   var info = this.getInfo();
   this.references = info.references;
   this.declarations = info.declarations;
+  this.declarationKinds = info.declarationKinds;
 }
 
 var vars = require("jshint/src/vars");
@@ -187,10 +188,15 @@ Scope.prototype.getInfo = function () {
   var info = block._scopeInfo = {};
   var references = info.references = {};
   var declarations = info.declarations = {};
+  var declarationKinds = info.declarationKinds = {};
 
   var add = function (node, reference, throwOnDuplicate) {
     self._add(node, references);
-    if (!reference) self._add(node, declarations, throwOnDuplicate);
+
+    if (!reference) {
+      self._add(node, declarations, throwOnDuplicate);
+      self._add(node, declarationKinds[node.kind] = declarationKinds[node.kind] || {});
+    }
   };
 
   if (parent && t.isBlockStatement(block) && t.isFor(parent.block)) {
@@ -240,7 +246,7 @@ Scope.prototype.getInfo = function () {
   // Function - params, rest
 
   if (t.isFunction(block)) {
-    add(block.rest);
+    if (block.rest) add(block.rest);
     _.each(block.params, function (param) {
       add(param);
     });
@@ -290,6 +296,24 @@ Scope.prototype.add = function (node) {
   scope._add(node, scope.references);
 };
 
+/**
+ * Walks the scope tree and gathers all declarations of `kind`.
+ *
+ * @returns {Object}
+ */
+
+Scope.prototype.getAllOfKind = function (kind) {
+  var ids = {};
+
+  var scope = this;
+  do {
+    _.defaults(ids, scope.declarationKinds[kind]);
+    scope = scope.parent;
+  } while (scope);
+
+  return ids;
+};
+
 /**
  * Description
  *