Don't include node in downcast error message.

pkg/analyzer/lib/src/task/strong/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.
 // TODO(jmesserly): this was ported from package:dev_compiler, and needs to be
 // refactored to fit into analyzer.
 library analyzer.src.task.strong.info;
 
@@ skipping 78 matching lines @@
       : super(rules, expression) {
     assert(_cast.toType != baseType &&
         _cast.fromType == baseType &&
         (baseType.isDynamic ||
             // Call methods make the following non-redundant
             _cast.toType.isSubtypeOf(baseType) ||
             baseType.isAssignableTo(_cast.toType)));
   }
 
   @override
-  List<Object> get arguments => [node, baseType, convertedType];
+  List<Object> get arguments => [baseType, convertedType];
 
   Cast get cast => _cast;
 
   DartType get convertedType => _cast.toType;
+
   @override
-  String get message => '{0} ({1}) will need runtime check '
-      'to cast to type {2}';
+  String get message => 'Unsound implicit cast from {0} to {1}';
 
   // Factory to create correct DownCast variant.
   static StaticInfo create(
       StrongTypeSystemImpl rules, Expression expression, Cast cast,
       {String reason}) {
     final fromT = cast.fromType;
     final toT = cast.toType;
 
     // toT <:_R fromT => to <: fromT
     // NB: classes with call methods are subtypes of function
@@ skipping 461 matching lines @@
 // TODO(vsm,leafp): Remove this.
 class UninferredClosure extends DownCast {
   UninferredClosure(TypeSystem rules, FunctionExpression expression, Cast cast)
       : super._internal(rules, expression, cast);
 
   @override
   String get name => 'STRONG_MODE_UNINFERRED_CLOSURE';
 
   toErrorCode() => new StaticTypeWarningCode(name, message);
 }