Fix generated server code to be strong mode compliant

pkg/analysis_server/tool/spec/codegen_dart_protocol.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 codegen.protocol;
 
 import 'dart:convert';
 
 import 'package:analyzer/src/codegen/tools.dart';
 import 'package:html/dom.dart' as dom;
@@ skipping 952 matching lines @@
       } else {
         return new FromJsonSnippet((String jsonPath, String json) {
           StringBuffer result = new StringBuffer();
           result.write('jsonDecoder.decodeMap($jsonPath, $json');
           if (!keyCode.isIdentity) {
             result.write(', keyDecoder: ${keyCode.asClosure}');
           }
           if (!valueCode.isIdentity) {
             result.write(', valueDecoder: ${valueCode.asClosure}');
           }
-          result.write(')');
+          result.write(') as ${dartType(type)}');
           return result.toString();
         });
       }
     } else if (type is TypeList) {
       FromJsonCode itemCode = fromJsonCode(type.itemType);
       if (itemCode.isIdentity) {
         return new FromJsonFunction('jsonDecoder.decodeList');
       } else {
         return new FromJsonSnippet((String jsonPath, String json) =>
-            'jsonDecoder.decodeList($jsonPath, $json, ${itemCode.asClosure})');
+            'jsonDecoder.decodeList($jsonPath, $json, ${itemCode.asClosure}) as ${dartType(type)}');

[Paul Berry, 2016/03/31 18:30:44]

Would it be possible to avoid the type cast by making decodeList a generic
function, so that instead of:

  jsonDecoder.decodeList(...) as List<Foo>

we do this instead?

  jsonDecoder.decodeList/*<Foo>*/(...)

       }
     } else if (type is TypeUnion) {
       List<String> decoders = <String>[];
       for (TypeDecl choice in type.choices) {
         TypeDecl resolvedChoice = resolveTypeReferenceChain(choice);
         if (resolvedChoice is TypeObject) {
           TypeObjectField field = resolvedChoice.getField(type.field);
           if (field == null) {
             throw new Exception(
                 'Each choice in the union needs a field named ${type.field}');
@@ skipping 239 matching lines @@
 
   @override
   String get asClosure => '($type value) => ${callback('value')}';
 
   @override
   bool get isIdentity => false;
 
   @override
   String asSnippet(String value) => callback(value);
 }