support patterns in constants

lib/6to5/transformers/constants.js

@@ -18,11 +18,33 @@ exports.ForStatement = function (node) {
   _.each(node.body, function (child) {
     if (child && child.type === "VariableDeclaration" && child.kind === "const") {
       _.each(child.declarations, function (declar) {
-        var name = declar.id.name;
-        check(declar, name);
+        var search = [declar.id];
+        var names  = [];
+
+        while (search.length) {
+          var id = search.shift();
+
+          if (id.type === "Identifier") {
+            names.push(id.name);
+          } else if (id.type === "ArrayPattern") {
+            _.each(id.elements, function (elem) {
+              search.push(elem);
+            });
+          } else if (id.type === "ObjectPattern") {
+            _.each(id.properties, function (prop) {
+              search.push(prop.value);
+            });
+          } else {
+            throw new Error("unknown node " + id.type);
+          }
+        }
+
+        _.each(names, function (name) {
+          check(declar, name);
+          constants.push(name);
+        });
 
         declar._ignoreConstant = true;
-        constants.push(name);
       });
       child.kind = "let";
     }