Handle for-in loops

lib/runtime/dart/collection.js

 var collection;
 (function(exports) {
   'use strict';
   let _source = Symbol('_source');
   let UnmodifiableListView$ = dart.generic(function(E) {
     class UnmodifiableListView extends _internal.UnmodifiableListBase$(E) {
       UnmodifiableListView(source) {
         this[_source] = source;
         super.UnmodifiableListBase();
       }
@@ skipping 330 matching lines @@
     }
     return SetBase;
   });
   let SetBase = SetBase$(dart.dynamic);
   let _HashSetBase$ = dart.generic(function(E) {
     class _HashSetBase extends SetBase$(E) {
       difference(other) {
         let result = this[_newSet]();
         for (let element of this) {
           if (!dart.notNull(other.contains(element)))
-            result.add(dart.as(element, E));
+            result.add(element);
         }
         return result;
       }
       intersection(other) {
         let result = this[_newSet]();
         for (let element of this) {
           if (other.contains(element))
-            result.add(dart.as(element, E));
+            result.add(element);
         }
         return result;
       }
       toSet() {
         return ((_) => {
           _.addAll(this);
           return _;
         }).bind(this)(this[_newSet]());
       }
     }
@@ skipping 28 matching lines @@
             equals = dart.closureWrap(_defaultEquals, "(E, E) → bool");
           }
         }
         return new _CustomHashSet(equals, hashCode, isValidKey);
       }
       HashSet$identity() {
         return new _IdentityHashSet();
       }
       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;
       }
     }
     dart.defineNamedConstructor(HashSet, 'identity');
     dart.defineNamedConstructor(HashSet, 'from');
     return HashSet;
   });
   let HashSet = HashSet$(dart.dynamic);
   let IterableMixin$ = dart.generic(function(E) {
@@ skipping 1702 matching lines @@
   let DoubleLinkedQueue$ = dart.generic(function(E) {
     class DoubleLinkedQueue extends IterableBase$(E) {
       DoubleLinkedQueue() {
         this[_sentinel] = null;
         this[_elementCount] = 0;
         super.IterableBase();
         this[_sentinel] = new _DoubleLinkedQueueEntrySentinel();
       }
       DoubleLinkedQueue$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$(E));
       }
       get length() {
         return this[_elementCount];
       }
       addLast(value) {
         this[_sentinel].prepend(value);
         this[_elementCount] = dart.notNull(this[_elementCount]) + 1;
@@ skipping 160 matching lines @@
           let sourceList = elements;
           queue[_table].setRange(0, length, dart.as(sourceList, core.Iterable$(E)), 0);
           queue[_tail] = length;
           return queue;
         } else {
           let capacity = ListQueue[_INITIAL_CAPACITY];
           if (dart.is(elements, _internal.EfficientLength)) {
             capacity = elements.length;
           }
           let result = new ListQueue(capacity);
-          for (let element of elements) {
+          for (let element of dart.as(elements, core.Iterable$(E))) {
             result.addLast(element);
           }
           return result;
         }
       }
       get iterator() {
         return new _ListQueueIterator(this);
       }
       forEach(action) {
         let modificationCount = this[_modificationCount];
@@ skipping 825 matching lines @@
         this[_comparator] = dart.as(compare === null ? core.Comparable.compare : compare, core.Comparator);
         this[_validKey] = dart.as(isValidKey !== null ? isValidKey : (v) => dart.is(v, E), _Predicate);
         super._SplayTree();
       }
       SplayTreeSet$from(elements, compare, isValidKey) {
         if (compare === void 0)
           compare = null;
         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$(E))) {
           result.add(element);
         }
         return result;
       }
       [_compare](e1, e2) {
         return dart.dinvokef(this[_comparator], e1, e2);
       }
       get iterator() {
         return new _SplayTreeKeyIterator(this);
       }
@@ skipping 1726 matching lines @@
   exports.LinkedHashMapKeyIterable = LinkedHashMapKeyIterable;
   exports.LinkedHashMapKeyIterable$ = LinkedHashMapKeyIterable$;
   exports.LinkedHashMapKeyIterator = LinkedHashMapKeyIterator;
   exports.LinkedHashMapKeyIterator$ = LinkedHashMapKeyIterator$;
   exports.HashSetIterator = HashSetIterator;
   exports.HashSetIterator$ = HashSetIterator$;
   exports.LinkedHashSetCell = LinkedHashSetCell;
   exports.LinkedHashSetIterator = LinkedHashSetIterator;
   exports.LinkedHashSetIterator$ = LinkedHashSetIterator$;
 })(collection || (collection = {}));