anchor.diff:        }
       }
   
  -    if (failed) {
  -      return const <_LinkedNode>[];
  -    }
       return dependencies.toList();
     }
   
  
positive.code:         _LinkedNode packageNode = packageToNode[package];
          if (packageNode == null) {
            failed = true;
          }
          dependencies.add(packageNode);
        } else {
          failed = true;
        }
      }
  
  
negative.code:     }
  
      // Link each package node.
  //    Stopwatch linkTimer = new Stopwatch()..start();
      for (_LinkedNode node in nodes) {
        if (!node.isEvaluated) {
          try {
            bool strong = context.analysisOptions.strongMode;
            new _LinkedWalker(store, strong).walk(node);
          } on _LinkException {
            // Linking of the node failed.
          }
        }
      }
      // TODO(scheglov) remove debug output after optimizing
  //    print('LINKED ${unlinkedBundles.length} bundles'
  //        ' in ${linkTimer.elapsedMilliseconds} ms');
  
      // Create successfully linked packages.
      List<LinkedPubPackage> linkedPackages = <LinkedPubPackage>[];
  