Second attempt to make dartc green.

dart/compiler/lib/implementation/collections.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /**
  * The [Collections] class implements static methods useful when
  * writing a class that implements [Collection] and the [iterator]
  * method.
  */
 class Collections {
@@ skipping 33 matching lines @@
       if (f(e)) destination.add(e);
     }
     return destination;
   }
 
   static bool isEmpty(Iterable<Object> iterable) {
     return !iterable.iterator().hasNext();
   }
 
   static String collectionToString(Collection c) => c.toString();
+
+  static void _emitObject(Object o, StringBuffer result, List visiting) {
+  }
 }