Use single unit/node/element.

pkg/analysis_server/lib/src/domain_analysis.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 domain.analysis;
 
 import 'dart:async';
 import 'dart:core';
 
 import 'package:analysis_server/plugin/analysis/analysis_domain.dart';
@@ skipping 72 matching lines @@
     return Response.DELAYED_RESPONSE;
   }
 
   /**
    * Implement the `analysis.getHover` request.
    */
   Future<Null> getHover(Request request) async {
     var params = new AnalysisGetHoverParams.fromRequest(request);
 
     // Prepare the resolved units.
-    List<CompilationUnit> units;
+    CompilationUnit unit;
     if (server.options.enableNewAnalysisDriver) {
       AnalysisResult result = await server.getAnalysisResult(params.file);
-      units = result != null ? [result.unit] : null;
+      unit = result?.unit;
     } else {
-      units = server.getResolvedCompilationUnits(params.file);
+      unit = server.getResolvedCompilationUnit(params.file);
     }
 
     // Prepare the hovers.
     List<HoverInformation> hovers = <HoverInformation>[];
-    for (CompilationUnit unit in units) {
+    if (unit != null) {
       HoverInformation hoverInformation =
           new DartUnitHoverComputer(unit, params.offset).compute();
       if (hoverInformation != null) {
         hovers.add(hoverInformation);
       }
     }
 
     // Send the response.
     server.sendResponse(
         new AnalysisGetHoverResult(hovers).toResponse(request.id));
@@ skipping 26 matching lines @@
     var params = new AnalysisGetNavigationParams.fromRequest(request);
     String file = params.file;
     Future<AnalysisDoneReason> analysisFuture =
         server.onFileAnalysisComplete(file);
     if (analysisFuture == null) {
       return new Response.getNavigationInvalidFile(request);
     }
     analysisFuture.then((AnalysisDoneReason reason) {
       switch (reason) {
         case AnalysisDoneReason.COMPLETE:
-          List<CompilationUnit> units =
-              server.getResolvedCompilationUnits(file);
-          if (units.isEmpty) {
+          CompilationUnit unit = server.getResolvedCompilationUnit(file);
+          if (unit == null) {
             server.sendResponse(new Response.getNavigationInvalidFile(request));
           } else {
-            CompilationUnitElement unitElement = units.first.element;
+            CompilationUnitElement unitElement = unit.element;
             NavigationCollectorImpl collector = computeNavigation(
                 server,
                 unitElement.context,
                 unitElement.source,
                 params.offset,
                 params.length);
             server.sendResponse(new AnalysisGetNavigationResult(
                     collector.files, collector.targets, collector.regions)
                 .toResponse(request.id));
           }
@@ skipping 248 matching lines @@
       context.onResultChanged(descriptor).listen((result) {
         StreamController<engine.ResultChangedEvent> controller =
             controllers[result.descriptor];
         if (controller != null) {
           controller.add(result);
         }
       });
     }
   }
 }