Use HasToJson when set Reponse/Notification parameters.

pkg/analysis_server/lib/src/computer/computer_hover.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 computer.hover;
 
 import 'dart:collection';
 
+import 'package:analysis_server/src/collections.dart';
 import 'package:analysis_server/src/constants.dart';
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/element.dart';
 
 
 /**
  * Converts [str] from a Dart Doc string with slashes and stars to a plain text
  * representation of the comment.
  */
 String _removeDartDocDelimiters(String str) {
@@ skipping 42 matching lines @@
  */
 class DartUnitHoverComputer {
   final CompilationUnit _unit;
   final int _offset;
 
   DartUnitHoverComputer(this._unit, this._offset);
 
   /**
    * Returns the computed hover, maybe `null`.
    */
-  Map<String, Object> compute() {
+  Hover compute() {
     AstNode node = new NodeLocator.con1(_offset).searchWithin(_unit);
     if (node is Expression) {
       Hover hover = new Hover(node.offset, node.length);
       // element
       Element element = ElementLocator.locateWithOffset(node, _offset);
       if (element != null) {
         // variable, if synthetic accessor
         if (element is PropertyAccessorElement) {
           PropertyAccessorElement accessor = element;
           if (accessor.isSynthetic) {
@@ skipping 13 matching lines @@
         String dartDoc = element.computeDocumentationComment();
         dartDoc = _removeDartDocDelimiters(dartDoc);
         hover.dartDoc = dartDoc;
       }
       // parameter
       hover.parameter = _safeToString(node.bestParameterElement);
       // types
       hover.staticType = _safeToString(node.staticType);
       hover.propagatedType = _safeToString(node.propagatedType);
       // done
-      return hover.toJson();
+      return hover;
     }
     // not an expression
     return null;
   }
 
   static _safeToString(obj) => obj != null ? obj.toString() : null;
 }
 
 
-class Hover {
+class Hover implements HasToJson {
   final int offset;
   final int length;
   String containingLibraryName;
   String containingLibraryPath;
   String dartDoc;
   String elementDescription;
   String elementKind;
   String parameter;
   String propagatedType;
   String staticType;
@@ skipping 39 matching lines @@
     }
     if (propagatedType != null) {
       json[PROPAGATED_TYPE] = propagatedType;
     }
     if (staticType != null) {
       json[STATIC_TYPE] = staticType;
     }
     return json;
   }
 }