Change ErrorNode to masquerade as a null literal.

dart/sdk/lib/_internal/compiler/implementation/warnings.dart

 // Copyright (c) 2011, 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.
 
 part of dart2js;
 
 const DONT_KNOW_HOW_TO_FIX = "";
 
 /**
  * The messages in this file should meet the following guide lines:
@@ skipping 1479 matching lines @@
 
   static const MessageKind ABSTRACT_METHOD = const MessageKind(
       "The method '#{name}' has no implementation in "
       "class '#{class}'.",
       howToFix: "Try adding a body to '#{name}' or declaring "
                 "'#{class}' to be 'abstract'.",
       examples: const ["""
 class Class {
   method();
 }
-main() => new Class();
+main() => new Class().method();
 """]);
 
   static const MessageKind ABSTRACT_GETTER = const MessageKind(
       "The getter '#{name}' has no implementation in "
       "class '#{class}'.",
       howToFix: "Try adding a body to '#{name}' or declaring "
                 "'#{class}' to be 'abstract'.",
       examples: const ["""
 class Class {
   get getter;
@@ skipping 204 matching lines @@
       examples: const ["""
 main() {
   var m = const {'foo': 1, 'foo': 2};
 }"""]);
 
   static const MessageKind BAD_INPUT_CHARACTER = const MessageKind(
       "Character U+#{characterHex} isn't allowed here.",
       howToFix: DONT_KNOW_HOW_TO_FIX,
       examples: const ["""
 main() {
-  print(ç);
+  String x = ç;
 }
 """]);
 
   static const MessageKind UNTERMINATED_STRING = const MessageKind(
       "String must end with #{quote}.",
       howToFix: DONT_KNOW_HOW_TO_FIX,
       examples: const ["""
 main() {
   return '
 ;
@@ skipping 304 matching lines @@
     return computeMessage();
   }
 
   bool operator==(other) {
     if (other is !Message) return false;
     return (kind == other.kind) && (toString() == other.toString());
   }
 
   int get hashCode => throw new UnsupportedError('Message.hashCode');
 }