Handle for-in loops

lib/runtime/dart/collection.js

Index: lib/runtime/dart/collection.js
diff --git a/lib/runtime/dart/collection.js b/lib/runtime/dart/collection.js
index 955c12a43897e6778a941264aec2cb11bfc34058..4892a7f7a6f900a2b24643f2b9873aaf941e3d4e 100644
--- a/lib/runtime/dart/collection.js
+++ b/lib/runtime/dart/collection.js
@@ -348,7 +348,7 @@ var collection;
         let result = this[_newSet]();
         for (let element of this) {
           if (!dart.notNull(other.contains(element)))
-            result.add(dart.as(element, E));
+            result.add(element);
         }
         return result;
       }
@@ -356,7 +356,7 @@ var collection;
         let result = this[_newSet]();
         for (let element of this) {
           if (other.contains(element))
-            result.add(dart.as(element, E));
+            result.add(element);
         }
         return result;
       }
@@ -405,7 +405,7 @@ var collection;
       }
       HashSet$from(elements) {
         let result = new HashSet();
-        for (let e of elements)
+        for (let e of dart.as(elements, core.Iterable$(E)))
           result.add(e);
         return result;
       }
@@ -2128,7 +2128,7 @@ var collection;
       }
       DoubleLinkedQueue$from(elements) {
         let list = dart.as(new DoubleLinkedQueue(), Queue$(E));
-        for (let e of elements) {
+        for (let e of dart.as(elements, core.Iterable$(E))) {
           list.addLast(e);
         }
         return dart.as(list, DoubleLinkedQueue$(E));
@@ -2309,7 +2309,7 @@ var collection;
             capacity = elements.length;
           }
           let result = new ListQueue(capacity);
-          for (let element of elements) {
+          for (let element of dart.as(elements, core.Iterable$(E))) {
             result.addLast(element);
           }
           return result;
@@ -3155,7 +3155,7 @@ var collection;
         if (isValidKey === void 0)
           isValidKey = null;
         let result = new SplayTreeSet(compare, isValidKey);
-        for (let element of elements) {
+        for (let element of dart.as(elements, core.Iterable$(E))) {
           result.add(element);
         }
         return result;