fix(change detection): Fix for comparing string by value

Author: vicb

lib/change_detection/dirty_checking_change_detector.dart

@@ -488,7 +488,7 @@ class _MapChangeRecord<K, V> implements MapChangeRecord<K, V> {
     _truncate(lastOldSeqRecord, oldSeqRecord);
     return isDirty;
   }
-  
+
   void _reset() {
     var record = _changesHead;
     while (record != null) {
@@ -577,7 +577,7 @@ class _MapChangeRecord<K, V> implements MapChangeRecord<K, V> {
       _removalsTail = record;
     }
   }
-  
+
   void _removeFromSeq(KeyValueRecord prev, KeyValueRecord record) {
     KeyValueRecord next = record._nextKeyValue;
     if (prev == null) _mapHead = next; else prev._nextKeyValue = next;
@@ -678,7 +678,7 @@ class _CollectionChangeRecord<K, V> implements CollectionChangeRecord<K, V> {
   }
 
   void forEachMove(void f(MovedItem<K, V> change)) {
-    ItemRecord record = _changesHead;
+    ItemRecord record = _movesHead;
     while(record != null) {
       f(record);
       record = record._nextMovedRec;
@@ -782,7 +782,7 @@ class _CollectionChangeRecord<K, V> implements CollectionChangeRecord<K, V> {
   mismatch(ItemRecord record, dynamic item, int index) {
     // Guard against bogus String changes
     if (record != null && item is String && record.item is String &&
-        record == item) {
+        record.item == item) {
       // this is false change in strings we need to recover, and pretend it is
       // the same. We save the value so that next time identity will pass
       return record..item = item;

test/change_detection/dirty_checking_change_detector_spec.dart

@@ -242,6 +242,16 @@ main() => describe('DirtyCheckingChangeDetector', () {
           removals: []));
     });
 
+    it('should test string by value rather than by reference', () {
+      var list = ['a', 'boo'];
+      var record = detector.watch(list, null, 'handler');
+      detector.collectChanges();
+
+      list[1] = 'b' + 'oo';
+
+      expect(detector.collectChanges()).toEqual(null);
+    });
+
     it('should remove and add same item', () {
       var list = ['a', 'b', 'c'];
       var record = detector.watch(list, null, 'handler');