reformat for of transformers and add pattern support

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

@@ -8,7 +8,7 @@ exports.ForOfStatement = function (node, parent, file, scope) {
   var stepKey   = file.generateUidIdentifier("step", scope);
   var stepValue = t.memberExpression(stepKey, t.identifier("value"));
 
-  if (t.isIdentifier(left)) {
+  if (t.isIdentifier(left) || t.isPattern(left)) {
     declar = t.expressionStatement(t.assignmentExpression("=", left, stepValue));
   } else if (t.isVariableDeclaration(left)) {
     declar = t.variableDeclaration(left.kind, [

lib/6to5/transformation/transformers/optional-for-of-fast.js

@@ -7,33 +7,31 @@ exports.ForOfStatement = function (node, parent, file, scope) {
   var left = node.left;
   var declar, id;
 
-  if (t.isIdentifier(left)) {
+  if (t.isIdentifier(left) || t.isPattern(left)) {
     id = left;
   } else if (t.isVariableDeclaration(left)) {
     id = left.declarations[0].id;
     declar = t.variableDeclaration(left.kind, [
       t.variableDeclarator(id)
     ]);
-  } else  {
+  } else {
     throw file.errorWithNode(left, "Unknown node type " + left.type + " in ForOfStatement");
   }
 
   var node2 = util.template("for-of-fast", {
     LOOP_OBJECT:  file.generateUidIdentifier("loopObject", scope),
     IS_ARRAY:     file.generateUidIdentifier("isArray", scope),
+    OBJECT:       node.right,
     INDEX:        file.generateUidIdentifier("i", scope),
-    ID:           id,
-    OBJECT:       node.right
+    ID:           id
   });
 
   t.inheritsComments(node2, node);
   t.ensureBlock(node);
 
   var block = node2.body;
-  if (declar) {
-    block.body.unshift(declar);
-  }
+  if (declar) block.body.unshift(declar);
   block.body = block.body.concat(node.body.body);
-  
+
   return node2;
 };