refactor optype to better filter invocation/prefixed suggestions

pkg/analysis_server/lib/src/services/completion/prefixed_element_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.completion.contributor.dart.invocation;
 
 import 'dart:async';
 
 import 'package:analysis_server/src/services/completion/dart_completion_manager.dart';
 import 'package:analysis_server/src/services/completion/local_declaration_visitor.dart';
 import 'package:analysis_server/src/services/completion/optype.dart';
 import 'package:analysis_server/src/services/completion/suggestion_builder.dart';
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/element.dart';
 
 import '../../protocol_server.dart' as protocol;
 import '../../protocol_server.dart'
     show CompletionSuggestion, CompletionSuggestionKind;
 
 /**
  * A contributor for calculating invocation / access suggestions
  * `completion.getSuggestions` request results.
  */
 class PrefixedElementContributor extends DartCompletionContributor {
   SuggestionBuilder builder;
 
   @override
   bool computeFast(DartCompletionRequest request) {
     OpType optype = request.optype;
-    if (optype.includeInvocationSuggestions) {
+    if (optype.isPrefixed) {
       builder = request.target.containingNode
           .accept(new _InvocationAstVisitor(request));
       if (builder != null) {
         return builder.computeFast(request.target.containingNode);
       }
     }
 
     return true;
   }
 
@@ skipping 310 matching lines @@
     }
     return new Future.value(false);
   }
 
   @override
   Future<bool> visitVariableElement(VariableElement element) {
     InterfaceTypeSuggestionBuilder.suggestionsFor(request, element.type);
     return new Future.value(true);
   }
 }