support destructuring in AssignmentStatement and ForOf loops

lib/6to5/transform.js

@@ -114,10 +114,10 @@ transform.transformers = {
   templateLiterals:         require("./transformers/template-literals"),
   propertyMethodAssignment: require("./transformers/property-method-assignment"),
   defaultParameters:        require("./transformers/default-parameters"),
-  destructuring:            require("./transformers/destructuring"),
   generators:               require("./transformers/generators"),
   blockBinding:             require("./transformers/block-binding"),
   restParameters:           require("./transformers/rest-parameters"),
   forOf:                    require("./transformers/for-of"),
+  destructuring:            require("./transformers/destructuring"),
   unicodeRegex:             require("./transformers/unicode-regex")
 };

lib/6to5/transformers/destructuring.js

@@ -2,15 +2,14 @@ var util = require("../util");
 var b    = require("ast-types").builders;
 var _    = require("lodash");
 
-var isPattern = function (id) {
-  return id.type === "ArrayPattern" || id.type === "ObjectPattern";
-};
-
-
 var buildVariableAssign = function (kind, id, init) {
-  return b.variableDeclaration(kind, [
-    b.variableDeclarator(id, init)
-  ]);
+  if (kind === false) {
+    return b.expressionStatement(b.assignmentExpression("=", id, init));
+  } else {
+    return b.variableDeclaration(kind, [
+      b.variableDeclarator(id, init)
+    ]);
+  }
 };
 
 var push = function (kind, nodes, pattern, parentId) {
@@ -26,7 +25,7 @@ var pushObjectPattern = function (kind, nodes, pattern, parentId) {
     var pattern2   = prop.value;
     var patternId2 = b.memberExpression(parentId, prop.key, false);
 
-    if (isPattern(pattern2)) {
+    if (util.isPattern(pattern2)) {
       push(kind, nodes, pattern2, patternId2);
     } else {
       nodes.push(buildVariableAssign(kind, pattern2, patternId2));
@@ -69,7 +68,7 @@ exports.FunctionExpression = function (node, parent, opts, generateUid) {
   var nodes = [];
 
   node.params = node.params.map(function (pattern) {
-    if (!isPattern(pattern)) return pattern;
+    if (!util.isPattern(pattern)) return pattern;
 
     var parentId = b.identifier(generateUid("ref"));
 
@@ -78,15 +77,35 @@ exports.FunctionExpression = function (node, parent, opts, generateUid) {
     return parentId;
   });
 
-  block.body = nodes.concat(block.body);
+  block.body = nodes.concat(block.body || []);
+};
+
+exports.ExpressionStatement = function (node, parent, opts, generateUid) {
+  var expr = node.expression;
+  if (expr.type !== "AssignmentExpression") return;
+
+  if (!util.isPattern(expr.left)) return;
+
+  var nodes = [];
+
+  var ref = b.identifier(generateUid("ref"));
+  nodes.push(b.variableDeclaration("var", [
+    b.variableDeclarator(ref, expr.right)
+  ]));
+
+  push(false, nodes, expr.left, ref);
+
+  return nodes;
 };
 
 exports.VariableDeclaration = function (node, parent, opts, generateUid) {
+  if (parent.type === "ForInStatement") return;
+
   var nodes = [];
 
   var hasPattern = false;
   _.each(node.declarations, function (declar) {
-    if (isPattern(declar.id)) {
+    if (util.isPattern(declar.id)) {
       hasPattern = true;
       return false;
     }
@@ -96,7 +115,7 @@ exports.VariableDeclaration = function (node, parent, opts, generateUid) {
   _.each(node.declarations, function (declar) {
     var patternId = declar.init;
     var pattern   = declar.id;
-    if (isPattern(pattern)) {
+    if (util.isPattern(pattern) && patternId) {
       pushPattern(node.kind, nodes, pattern, patternId, generateUid);
     } else {
       nodes.push(buildVariableAssign(node.kind, declar.id, declar.init));

lib/6to5/transformers/for-of.js

@@ -1,18 +1,39 @@
 var util = require("../util");
+var b    = require("ast-types").builders;
 
 exports.ForOfStatement = function (node, parent, opts, generateUid) {
+  var declar;
+  var isPattern = false;
+
+  var key;
+  if (node.left.type === "VariableDeclaration") {
+    declar = node.left;
+    key = declar.declarations[0].id;
+  } else {
+    isPattern = true;
+    declar = node.left[0];
+    key = b.identifier(generateUid("ref"));
+  }
+
   var node2 = util.template("for-of", {
     ITERATOR_KEY: generateUid("iterator"),
     STEP_KEY:     generateUid("step"),
     OBJECT:       node.right,
-    KEY:          node.left.declarations[0].id
+    KEY:          key
   });
 
   var block  = node2.body;
-  block.body = block.body.concat(node.body.body);
+
+  if (isPattern) {
+    block.body.push(b.variableDeclaration(declar.kind, [
+      b.variableDeclarator(declar.declarations[0].id, key)
+    ]));
+  }
+
+  block.body = block.body.concat(node.body.body || []);
 
   var declar  = block.body[0];
-  declar.kind = node.left.kind;
+  declar.kind = declar.kind;
 
   return node2;
 };

lib/6to5/util.js

@@ -11,15 +11,15 @@ _.each(esprima.Syntax, function (name) {
   estraverse.VisitorKeys[name] = estraverse.VisitorKeys[name] || [];
 });
 
-exports.parse = function (filename, code, callback) {
+exports.parse = function (filename, code, callback, opts) {
   try {
-    var ast = esprima.parse(code, {
+    var ast = esprima.parse(code, _.extend(opts || {}, {
       comment: true,
       source:  filename,
       tokens:  true,
       range:   true,
       loc:     true
-    });
+    }));
 
     estraverse.attachComments(ast, ast.comments, ast.tokens);
 
@@ -41,6 +41,10 @@ exports.parse = function (filename, code, callback) {
   }
 };
 
+exports.isPattern = function (node) {
+  return node.type === "ArrayPattern" || node.type === "ObjectPattern";
+};
+
 exports.generate = function (ast, opts) {
   opts = opts || {};
 
@@ -218,6 +222,8 @@ try {
     var loc  = templatesLoc + "/" + name;
     var code = fs.readFileSync(loc, "utf8");
 
-    exports.templates[key] = exports.removeProperties(exports.parse(loc, code));
+    exports.templates[key] = exports.removeProperties(exports.parse(loc, code, null, {
+      tolerant: true
+    }));
   });
 }

test/fixtures/destructuring/assignment/actual.js

@@ -0,0 +1 @@
+[a, b] = f();

test/fixtures/destructuring/assignment/expected.js

@@ -0,0 +1,3 @@
+var _ref = f();
+a = _ref[0];
+b = _ref[1];

test/fixtures/destructuring/for-in/actual.js

@@ -0,0 +1,3 @@
+for (var [name, value] in obj) {
+  print("Name: " + name + ", Value: " + value);
+}

test/fixtures/destructuring/for-in/expected.js

@@ -0,0 +1,4 @@
+for (var name in obj) {
+  var value = obj[name];
+  print("Name: " + name + ", Value: " + value);
+}

test/fixtures/destructuring/for-of/actual.js

@@ -0,0 +1,3 @@
+for (var [ name, before, after ] of this.test.expectation.registers) {
+
+}

test/fixtures/destructuring/for-of/expected.js

@@ -0,0 +1,5 @@
+for (var _iterator = this.test.expectation.registers[Symbol.iterator](), _step; !(_step = _iterator.next()).done;) {
+  var name = _step.value[0];
+  var before = _step.value[1];
+  var after = _step.value[2];
+}