Make mappedBy lazy.

utils/pub/utils.dart

 // Copyright (c) 2012, 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.
 
 /**
  * Generic utility functions. Stuff that should possibly be in core.
  */
 library utils;
 
 import 'dart:async';
@@ skipping 37 matching lines @@
   future.then((_) => fn());
   future.handleException((_) {
     fn();
     return false;
   });
 }
 
 /**
  * Flattens nested lists into a single list containing only non-list elements.
  */
-List flatten(List nested) {
+List flatten(Iterable nested) {
   var result = [];
   helper(list) {
     for (var element in list) {
       if (element is List) {
         helper(element);
       } else {
         result.add(element);
       }
     }
   }
@@ skipping 55 matching lines @@
   CryptoUtils.bytesToHex(new SHA1().update(source.charCodes).digest());
 
 /**
  * Returns a [Future] that completes in [milliSeconds].
  */
 Future sleep(int milliSeconds) {
   var completer = new Completer();
   new Timer(milliSeconds, completer.complete);
   return completer.future;
 }