Make implicit casts hints

lib/src/info.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.
 
 /// Defines static information collected by the type checker and used later by
 /// emitters to generate code.
 library dev_compiler.src.info;
 
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/element.dart';
@@ skipping 314 matching lines @@
 
   toErrorCode() => new StaticTypeWarningCode(name, message);
 }
 
 // A down cast to a non-ground type.  These behave differently from standard
 // Dart and may be more likely to fail at runtime.
 class DownCastImplicit extends DownCast {
   DownCastImplicit(TypeRules rules, Expression expression, Cast cast)
       : super._internal(rules, expression, cast);
 
-  toErrorCode() => new StaticTypeWarningCode(name, message);
+  toErrorCode() => new HintCode(name, message);
 }
 
 // An inferred type for the wrapped expression, which may need to be
 // reified into the term
 abstract class InferredTypeBase extends CoercionInfo {
   final DartType _type;
 
   InferredTypeBase._internal(TypeRules rules, Expression expression, this._type)
       : super(rules, expression);
 
@@ skipping 227 matching lines @@
 /// Better to have `super` at the end, as required by the Dart style guide:
 /// <http://goo.gl/q1T4BB>
 ///
 /// For now this is the only pattern we support.
 class InvalidSuperInvocation extends StaticError {
   InvalidSuperInvocation(SuperConstructorInvocation node) : super(node);
 
   @override String get message => "super call must be last in an initializer "
       "list (see http://goo.gl/q1T4BB): {0}";
 }