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

@@ -20,11 +20,7 @@ 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);
-    }
+    block.body.push(declar);
   }
 
   // push the rest of the original loop body onto our new 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");
@@ -61,10 +57,15 @@ 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
+    declar: declar,
+    loop:   loop
   };
 };