refactor optype to be computed once per refactoring request

pkg/analysis_server/lib/src/services/completion/dart_completion_manager.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.completion.dart;
 
 import 'dart:async';
 
 import 'package:analysis_server/src/protocol.dart';
 import 'package:analysis_server/src/services/completion/arglist_computer.dart';
 import 'package:analysis_server/src/services/completion/combinator_computer.dart';
 import 'package:analysis_server/src/services/completion/completion_manager.dart';
 import 'package:analysis_server/src/services/completion/dart_completion_cache.dart';
 import 'package:analysis_server/src/services/completion/imported_computer.dart';
 import 'package:analysis_server/src/services/completion/invocation_computer.dart';
 import 'package:analysis_server/src/services/completion/keyword_computer.dart';
 import 'package:analysis_server/src/services/completion/local_computer.dart';
+import 'package:analysis_server/src/services/completion/optype.dart';
 import 'package:analysis_server/src/services/search/search_engine.dart';
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/source.dart';
 
 /**
  * The base class for computing code completion suggestions.
  */
 abstract class DartCompletionComputer {
   /**
@@ skipping 202 matching lines @@
   CompilationUnit unit;
 
   /**
    * The node in which the completion occurred. This node
    * may or may not be resolved when [DartCompletionComputer.computeFast]
    * is called but is resolved when [DartCompletionComputer.computeFull].
    */
   AstNode node;
 
   /**
+   * Information about the types of suggestions that should be included.
+   */
+  OpType _optype;
+
+  /**
    * The offset of the start of the text to be replaced.
    * This will be different than the offset used to request the completion
    * suggestions if there was a portion of an identifier before the original
    * offset. In particular, the replacementOffset will be the offset of the
    * beginning of said identifier.
    */
   int replacementOffset;
 
   /**
    * The length of the text to be replaced if the remainder of the identifier
@@ skipping 12 matching lines @@
       : super(offset, performance);
 
   /**
    * Return the original text from the [replacementOffset] to the [offset]
    * that can be used to filter the suggestions on the server side.
    */
   String get filterText {
     return context.getContents(
         source).data.substring(replacementOffset, offset);
   }
+
+  /**
+   * Information about the types of suggestions that should be included.
+   * This will return `null` if the [node] has not been set.
+   */
+  OpType get optype {
+    if (_optype == null && node != null) {
+      _optype = new OpType.forCompletion(node, offset);
+    }
+    return _optype;
+  }
 }
 
 /**
  * Visitor used to determine the replacement offset and length
  * based upon the cursor location.
  */
 class _ReplacementOffsetBuilder extends SimpleAstVisitor {
   final DartCompletionRequest request;
 
   _ReplacementOffsetBuilder(this.request) {
     request.replacementOffset = request.offset;
     request.replacementLength = 0;
   }
 
   visitSimpleIdentifier(SimpleIdentifier node) {
     request.replacementOffset = node.offset;
     request.replacementLength = node.length;
   }
 }