Add --no-declaration-casts option to analyzer.

pkg/analyzer/lib/src/task/options.dart

 // 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.
 
 library analyzer.src.task.options;
 
 import 'dart:collection';
 
 import 'package:analyzer/analyzer.dart';
 import 'package:analyzer/plugin/options.dart';
@@ skipping 40 matching lines @@
   static const String enableSuperMixins = 'enableSuperMixins';
 
   static const String errors = 'errors';
   static const String exclude = 'exclude';
   static const String include = 'include';
   static const String language = 'language';
   static const String plugins = 'plugins';
   static const String strong_mode = 'strong-mode';
 
   // Strong mode options, see AnalysisOptionsImpl for documentation.
+  static const String declarationCasts = 'declaration-casts';
   static const String implicitCasts = 'implicit-casts';
   static const String implicitDynamic = 'implicit-dynamic';
 
   /// Ways to say `ignore`.
   static const List<String> ignoreSynonyms = const ['ignore', 'false'];
 
   /// Valid error `severity`s.
   static final List<String> severities =
       new List.unmodifiable(severityMap.keys);
 
@@ skipping 495 matching lines @@
 
   void _applyProcessors(AnalysisOptionsImpl options, Object codes) {
     ErrorConfig config = new ErrorConfig(codes);
     options.errorProcessors = config.processors;
   }
 
   void _applyStrongModeOption(
       AnalysisOptionsImpl options, Object feature, Object value) {
     bool boolValue = toBool(value);
     if (boolValue != null) {
+      if (feature == AnalyzerOptions.declarationCasts) {
+        options.declarationCasts = boolValue;
+      }
       if (feature == AnalyzerOptions.implicitCasts) {
         options.implicitCasts = boolValue;
       }
       if (feature == AnalyzerOptions.implicitDynamic) {
         options.implicitDynamic = boolValue;
       }
     }
   }
 
   void _applyStrongOptions(AnalysisOptionsImpl options, Object config) {
     if (config is YamlMap) {
       options.strongMode = true;
       config.nodes.forEach((k, v) {
         if (k is YamlScalar && v is YamlScalar) {
           _applyStrongModeOption(options, k.value?.toString(), v.value);
         }
       });
     } else if (config is Map) {
       options.strongMode = true;
       config.forEach((k, v) => _applyStrongModeOption(options, k, v));
     } else {
       options.strongMode = config is bool ? config : false;
     }
   }
 }