Deprecate the generated AST library and clean up imports

pkg/analysis_server/lib/src/services/index/index_contributor.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.
 
 library services.src.index.index_contributor;
 
 import 'dart:collection' show Queue;
 
 import 'package:analysis_server/src/provisional/index/index_core.dart';
 import 'package:analysis_server/src/services/correction/namespace.dart';
 import 'package:analysis_server/src/services/index/index.dart';
 import 'package:analysis_server/src/services/index/index_store.dart';
 import 'package:analysis_server/src/services/index/indexable_element.dart';
 import 'package:analysis_server/src/services/index/indexable_file.dart';
+import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
+import 'package:analyzer/dart/ast/visitor.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
-import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/java_engine.dart';
 import 'package:analyzer/src/generated/source.dart';
 
 /**
  * An [IndexContributor] that contributes relationships for Dart files.
  */
 class DartIndexContributor extends IndexContributor {
   @override
   void contributeTo(IndexStore store, AnalysisContext context, Object object) {
@@ skipping 802 matching lines @@
   }
 
   /**
    * @return `true` if given "node" is part of [PrefixedIdentifier] "prefix.node".
    */
   static bool _isIdentifierInPrefixedIdentifier(SimpleIdentifier node) {
     AstNode parent = node.parent;
     return parent is PrefixedIdentifier && parent.identifier == node;
   }
 }