Emit a compile-time error when the name of a variable is referenced in the

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 620 matching lines @@
   // This is used as an exception.
   static const MessageKind INVALID_SOURCE_FILE_LOCATION = const MessageKind('''
 Invalid offset (#{offset}) in source map.
 File: #{fileName}
 Length: #{length}''');
 
   static const MessageKind TOP_LEVEL_VARIABLE_DECLARED_STATIC =
       const MessageKind(
           'Error: Top-level variable cannot be declared static.');
 
+  static const MessageKind REFERENCE_IN_INITIALIZATION = const MessageKind(
+       "Error: Variable '#{variableName}' is referenced during its "
+       "initialization.",
+       howToFix: "If you are trying to reference a shadowed variable, rename"
+         " one of the variables.",
+       examples: const ["""
+foo(t) {
+  var t = t;
+  return t;
+}
+
+main() => foo(1);
+"""]);
+
+
   static const MessageKind WRONG_NUMBER_OF_ARGUMENTS_FOR_ASSERT =
       const MessageKind(
           'Error: Wrong number of arguments to assert. Should be 1, but given '
           '#{argumentCount}.');
 
   static const MessageKind ASSERT_IS_GIVEN_NAMED_ARGUMENTS = const MessageKind(
       'Error: "assert" takes no named arguments, but given #{argumentCount}.');
 
   static const MessageKind FACTORY_REDIRECTION_IN_NON_FACTORY =
       const MessageKind(
@@ skipping 434 matching lines @@
 
 class CompileTimeConstantError extends Diagnostic {
   CompileTimeConstantError(MessageKind kind, Map arguments, bool terse)
     : super(kind, arguments, terse);
 }
 
 class CompilationError extends Diagnostic {
   CompilationError(MessageKind kind, Map arguments, bool terse)
     : super(kind, arguments, terse);
 }