Issue 13239. Add the 'Encapsulate Field' refactoring.

pkg/analysis_server/lib/src/services/correction/assist.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.correction.assist;
 
 import 'package:analysis_server/src/protocol.dart';
 import 'package:analysis_server/src/services/correction/assist_internal.dart';
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/source.dart';
@@ skipping 39 matching lines @@
   static const CONVERT_INTO_BLOCK_BODY = const AssistKind(
       'CONVERT_INTO_BLOCK_BODY', 30, "Convert into block body");
   static const CONVERT_INTO_EXPRESSION_BODY = const AssistKind(
       'CONVERT_INTO_EXPRESSION_BODY', 30, "Convert into expression body");
   static const CONVERT_INTO_FOR_INDEX = const AssistKind(
       'CONVERT_INTO_FOR_INDEX', 30, "Convert into for-index loop");
   static const CONVERT_INTO_IS_NOT =
       const AssistKind('CONVERT_INTO_IS_NOT', 30, "Convert into is!");
   static const CONVERT_INTO_IS_NOT_EMPTY = const AssistKind(
       'CONVERT_INTO_IS_NOT_EMPTY', 30, "Convert into 'isNotEmpty'");
+  static const ENCAPSULATE_FIELD =
+      const AssistKind('ENCAPSULATE_FIELD', 30, "Encapsulate field");
   static const EXCHANGE_OPERANDS =
       const AssistKind('EXCHANGE_OPERANDS', 30, "Exchange operands");
   static const EXTRACT_CLASS =
       const AssistKind('EXTRACT_CLASS', 30, "Extract class into file '{0}'");
   static const IMPORT_ADD_SHOW =
       const AssistKind('IMPORT_ADD_SHOW', 30, "Add explicit 'show' combinator");
   static const INTRODUCE_LOCAL_CAST_TYPE = const AssistKind(
       'INTRODUCE_LOCAL_CAST_TYPE', 30, "Introduce new local with tested type");
   static const INVERT_IF_STATEMENT =
       const AssistKind('INVERT_IF_STATEMENT', 30, "Invert 'if' statement");
@@ skipping 34 matching lines @@
 
   final name;
   final int relevance;
   final String message;
 
   const AssistKind(this.name, this.relevance, this.message);
 
   @override
   String toString() => name;
 }