add improved for-of loose behaviour that supports destructuring - fixes #615

lib/6to5/transformation/templates/for-of-loose.js

@@ -2,6 +2,7 @@ for (var LOOP_OBJECT = OBJECT,
          IS_ARRAY = Array.isArray(LOOP_OBJECT),
          INDEX = 0,
          LOOP_OBJECT = IS_ARRAY ? LOOP_OBJECT : LOOP_OBJECT[Symbol.iterator]();;) {
+  var ID;
   if (IS_ARRAY) {
     if (INDEX >= LOOP_OBJECT.length) break;
     ID = LOOP_OBJECT[INDEX++];

lib/6to5/transformation/transformers/es6/for-of.js

@@ -20,12 +20,8 @@ exports.ForOfStatement = function (node, parent, scope, context, file) {
 
   // add the value declaration to the new loop body
   if (declar) {
-    if (build.shouldUnshift) {
-      block.body.unshift(declar);
-    } else {
     block.body.push(declar);
   }
-  }
 
   // push the rest of the original loop body onto our new body
   block.body = block.body.concat(node.body.body);
@@ -45,9 +41,9 @@ var loose = function (node, parent, scope, context, file) {
     id = left;
   } else if (t.isVariableDeclaration(left)) {
     // for (var i of test)
-    id = left.declarations[0].id;
+    id = scope.generateUidIdentifier("ref");
     declar = t.variableDeclaration(left.kind, [
-      t.variableDeclarator(id)
+      t.variableDeclarator(left.declarations[0].id, id)
     ]);
   } else {
     throw file.errorWithNode(left, "Unknown node type " + left.type + " in ForOfStatement");
@@ -61,8 +57,13 @@ var loose = function (node, parent, scope, context, file) {
     ID:           id
   });
 
+  if (!declar) {
+    // no declaration so we need to remove the variable declaration at the top of
+    // the for-of-loose template
+    loop.body.body.shift();
+  }
+
   return {
-    shouldUnshift: true,
     declar: declar,
     loop:   loop
   };

test/fixtures/transformation/es6-for-of-loose/let/expected.js

@@ -1,13 +1,14 @@
 "use strict";
 
 for (var _iterator = arr, _isArray = Array.isArray(_iterator), _i = 0, _iterator = _isArray ? _iterator : _iterator[Symbol.iterator]();;) {
-  var i = undefined;
+  var _ref;
   if (_isArray) {
     if (_i >= _iterator.length) break;
-    i = _iterator[_i++];
+    _ref = _iterator[_i++];
   } else {
     _i = _iterator.next();
     if (_i.done) break;
-    i = _i.value;
+    _ref = _i.value;
   }
+  var i = _ref;
 }

test/fixtures/transformation/es6-for-of-loose/multiple/expected.js

@@ -1,25 +1,27 @@
 "use strict";
 
 for (var _iterator = arr, _isArray = Array.isArray(_iterator), _i = 0, _iterator = _isArray ? _iterator : _iterator[Symbol.iterator]();;) {
-  var i;
+  var _ref;
   if (_isArray) {
     if (_i >= _iterator.length) break;
-    i = _iterator[_i++];
+    _ref = _iterator[_i++];
   } else {
     _i = _iterator.next();
     if (_i.done) break;
-    i = _i.value;
+    _ref = _i.value;
   }
+  var i = _ref;
 }
 
 for (var _iterator2 = numbers, _isArray2 = Array.isArray(_iterator2), _i2 = 0, _iterator2 = _isArray2 ? _iterator2 : _iterator2[Symbol.iterator]();;) {
-  var i;
+  var _ref2;
   if (_isArray2) {
     if (_i2 >= _iterator2.length) break;
-    i = _iterator2[_i2++];
+    _ref2 = _iterator2[_i2++];
   } else {
     _i2 = _iterator2.next();
     if (_i2.done) break;
-    i = _i2.value;
+    _ref2 = _i2.value;
   }
+  var i = _ref2;
 }

test/fixtures/transformation/es6-for-of-loose/var/expected.js

@@ -1,13 +1,14 @@
 "use strict";
 
 for (var _iterator = arr, _isArray = Array.isArray(_iterator), _i = 0, _iterator = _isArray ? _iterator : _iterator[Symbol.iterator]();;) {
-  var i;
+  var _ref;
   if (_isArray) {
     if (_i >= _iterator.length) break;
-    i = _iterator[_i++];
+    _ref = _iterator[_i++];
   } else {
     _i = _iterator.next();
     if (_i.done) break;
-    i = _i.value;
+    _ref = _i.value;
   }
+  var i = _ref;
 }