refactor optype to be computed once per refactoring request

pkg/analysis_server/lib/src/services/completion/imported_computer.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.computer.dart.toplevel;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:analysis_server/src/protocol_server.dart' hide Element,
     ElementKind;
 import 'package:analysis_server/src/services/completion/dart_completion_cache.dart';
 import 'package:analysis_server/src/services/completion/dart_completion_manager.dart';
-import 'package:analysis_server/src/services/completion/optype_ast_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';
 
 /**
  * A computer for calculating imported class and top level variable
  * `completion.getSuggestions` request results.
  */
 class ImportedComputer extends DartCompletionComputer {
   bool shouldWaitForLowPrioritySuggestions;
   _ImportedSuggestionBuilder builder;
 
   ImportedComputer({this.shouldWaitForLowPrioritySuggestions: false});
 
   @override
   bool computeFast(DartCompletionRequest request) {
-
-    // Determine the type of suggestions to be made
-    OpTypeAstVisitor opTypeVisitor = new OpTypeAstVisitor(request.offset);
-    request.node.accept(opTypeVisitor);
-
-    // Build the suggestions
-    if (opTypeVisitor.includeTopLevelSuggestions) {
+    OpType optype = request.optype;
+    if (optype.includeTopLevelSuggestions) {
       builder = new _ImportedSuggestionBuilder(
           request,
-          typesOnly: opTypeVisitor.includeOnlyTypeNameSuggestions,
-          excludeVoidReturn: !opTypeVisitor.includeVoidReturnSuggestions);
+          typesOnly: optype.includeOnlyTypeNameSuggestions,
+          excludeVoidReturn: !optype.includeVoidReturnSuggestions);
       builder.shouldWaitForLowPrioritySuggestions =
           shouldWaitForLowPrioritySuggestions;
       return builder.computeFast(request.node);
     }
     return true;
   }
 
   @override
   Future<bool> computeFull(DartCompletionRequest request) {
     if (builder != null) {
@@ skipping 144 matching lines @@
     addFilteredSuggestions(cache.importedTypeSuggestions);
     addFilteredSuggestions(cache.libraryPrefixSuggestions);
     if (!typesOnly) {
       addFilteredSuggestions(cache.otherImportedSuggestions);
       if (!excludeVoidReturn) {
         addFilteredSuggestions(cache.importedVoidReturnSuggestions);
       }
     }
   }
 }