anchor.diff:  import 'package:analysis_server/src/services/completion/dart/uri_contributor.dart';
   import 'package:analysis_server/src/services/completion/dart/variable_name_contributor.dart';
   import 'package:analyzer/dart/analysis/results.dart';
  +import 'package:analyzer/dart/analysis/session.dart';
   import 'package:analyzer/dart/ast/ast.dart';
   import 'package:analyzer/dart/element/element.dart';
   import 'package:analyzer/dart/element/type.dart';
  
positive.code:       new UriContributor(),
        new VariableNameContributor()
      ];
      for (DartCompletionContributor contributor in contributors) {
        String contributorTag =
            'DartCompletionManager - ${contributor.runtimeType}';
        performance.logStartTime(contributorTag);
        List<CompletionSuggestion> contributorSuggestions =
            await contributor.computeSuggestions(dartRequest);
        performance.logElapseTime(contributorTag);
        request.checkAborted();
  
        for (CompletionSuggestion newSuggestion in contributorSuggestions) {
          String key = newSuggestion.completion;
  
          // Append parenthesis for constructors to disambiguate from classes.
          if (_isConstructor(newSuggestion)) {
            key += '()';
            String className = _getConstructorClassName(newSuggestion);
            _ensureList(constructorMap, className).add(key);
          }
  
          // Local declarations hide both the class and its constructors.
          if (!_isClass(newSuggestion)) {
            List<String> constructorKeys = constructorMap[key];
            constructorKeys?.forEach(suggestionMap.remove);
          }
  
          CompletionSuggestion oldSuggestion = suggestionMap[key];
          if (oldSuggestion == null ||
              oldSuggestion.relevance < newSuggestion.relevance) {
            suggestionMap[key] = newSuggestion;
          }
        }
      }
  
      // Adjust suggestion relevance before returning
  
negative.code: // Copyright (c) 2015, 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.
  
  import 'dart:async';
  
  import 'package:analysis_server/src/provisional/completion/completion_core.dart'
      show AbortCompletion, CompletionContributor, CompletionRequest;
  import 'package:analysis_server/src/provisional/completion/dart/completion_dart.dart';
  import 'package:analysis_server/src/services/completion/completion_core.dart';
  import 'package:analysis_server/src/services/completion/completion_performance.dart';
  