Explicitly document that NavigationRegion.targets cannot be empty.

pkg/analysis_server/lib/src/generated_protocol.dart

 // Copyright (c) 2014, 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.
 //
 // This file has been automatically generated.  Please do not edit it manually.
 // To regenerate the file, use the script
 // "pkg/analysis_server/tool/spec/generate_files".
 
 part of protocol;
 /**
@@ skipping 11135 matching lines @@
    * The length of the region from which the user can navigate.
    */
   void set length(int value) {
     assert(value != null);
     this._length = value;
   }
 
   /**
    * The indexes of the targets (in the enclosing navigation response) to which
    * the given region is bound. By opening the target, clients can implement
-   * one form of navigation.
+   * one form of navigation. This list cannot be empty.
    */
   List<int> get targets => _targets;
 
   /**
    * The indexes of the targets (in the enclosing navigation response) to which
    * the given region is bound. By opening the target, clients can implement
-   * one form of navigation.
+   * one form of navigation. This list cannot be empty.
    */
   void set targets(List<int> value) {
     assert(value != null);
     this._targets = value;
   }
 
   NavigationRegion(int offset, int length, List<int> targets) {
     this.offset = offset;
     this.length = length;
     this.targets = targets;
@@ skipping 4418 matching lines @@
     return false;
   }
 
   @override
   int get hashCode {
     int hash = 0;
     hash = _JenkinsSmiHash.combine(hash, newName.hashCode);
     return _JenkinsSmiHash.finish(hash);
   }
 }